to #26424323

Since we concern idle, let's take idle as the center state. And omit
transition between other stats. Below is the state transition graph:

                                sleep->deque
+-----------+ cpumask +-------+ exit->deque +-------+
|ineffective|-------- | idle  | <-----------|running|
+-----------+         +-------+             +-------+
                        ^ |
 unthrtl child -> deque | |
          wake -> deque | |thrtl chlid -> enque
       migrate -> deque | |migrate -> enque
                        | v
                      +-------+
                      | steal |
                      +-------+

We conclude idle state condition as:

!se->on_rq && !my_q->throttled && cpu allowed.

From this graph and condition, we can hook (de|en)queue_task_fair
update_cpumasks_hier, (un|)throttle_cfs_rq to account idle state.

In the hooked functions, we also check the conditions, to avoid
accounting unwanted cpu clocks.
Signed-off-by: NYihao Wu <wuyihao@linux.alibaba.com>
Signed-off-by: NShanpei Chen <shanpeic@linux.alibaba.com>
Acked-by: NMichael Wang <yun.wang@linux.alibaba.com>

to #26424323

It's relatively easy to maintain nr_uninterruptible in scheduler
compared to doing it in cpuacct, we assume that "cpu,cpuacct" are
bound together, so that it can be used for per-cgroup load.

This will be needed to calculate per-cgroup load average later.
Reviewed-by: NMichael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: NXunlei Pang <xlpang@linux.alibaba.com>
Signed-off-by: NYihao Wu <wuyihao@linux.alibaba.com>

fix #25892693

commit 26a8b12747c975b33b4a82d62e4a307e1c07f31b upstream

Currently, there is a potential race between distribute_cfs_runtime()
and assign_cfs_rq_runtime(). Race happens when cfs_b->runtime is read,
distributes without holding lock and finds out there is not enough
runtime to charge against after distribution. Because
assign_cfs_rq_runtime() might be called during distribution, and use
cfs_b->runtime at the same time.

Fibtest is the tool to test this race. Assume all gcfs_rq is throttled
and cfs period timer runs, slow threads might run and sleep, returning
unused cfs_rq runtime and keeping min_cfs_rq_runtime in their local
pool. If all this happens sufficiently quickly, cfs_b->runtime will drop
a lot. If runtime distributed is large too, over-use of runtime happens.

A runtime over-using by about 70 percent of quota is seen when we
test fibtest on a 96-core machine. We run fibtest with 1 fast thread and
95 slow threads in test group, configure 10ms quota for this group and
see the CPU usage of fibtest is 17.0%, which is far from than the
expected 10%.

On a smaller machine with 32 cores, we also run fibtest with 96
threads. CPU usage is more than 12%, which is also more than expected
10%. This shows that on similar workloads, this race do affect CPU
bandwidth control.

Solve this by holding lock inside distribute_cfs_runtime().

Fixes: c06f04c7 ("sched: Fix potential near-infinite distribute_cfs_runtime() loop")
Signed-off-by: NHuaixin Chang <changhuaixin@linux.alibaba.com>
Reviewed-by: NBen Segall <bsegall@google.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
Link: https://lore.kernel.org/lkml/20200325092602.22471-1-changhuaixin@linux.alibaba.com/Signed-off-by: NYihao Wu <wuyihao@linux.alibaba.com>

For a long time runnable cpu load has been used in selecting task rq
when waking up tasks. Recent test has shown for test load with a large
quantity of short running tasks and almost full cpu utility, static load
is more helpful.

In our e2e tests, runnable load avg of java threads ranges from less than
10 to as large as 362, while these java threads are no different from
each other, and should be treated in the same way. After using static
load, qps imporvement has been seen in multiple test cases.

A new sched feature WA_STATIC_WEIGHT is introduced here to control. Echo
WA_STATIC_WEIGHT to /sys/kernel/debug/sched_features to turn static load
in wake_affine_weight on and NO_WA_STATIC_WEIGHT to turn it off. This
feature is kept off by default.

Test is done on the following hardware:

4 threads Intel(R) Xeon(R) Platinum 8269CY CPU @ 2.50GHz

In tests with 120 threads and sql loglevel configured to info:

	NO_WA_STATIC_WEIGHT     WA_STATIC_WEIGHT
	33170.63                34614.95 (+4.35%)

In tests with 160 threads and sql loglevel configured to info:

	NO_WA_STATIC_WEIGHT     WA_STATIC_WEIGHT
	35888.71                38247.20 (+6.57%)

In tests with 160 threads and sql loglevel configured to warn:

	NO_WA_STATIC_WEIGHT     WA_STATIC_WEIGHT
	39118.72                39698.72 (+1.48%)
Signed-off-by: NHuaixin Chang <changhuaixin@linux.alibaba.com>
Acked-by: NShanpei Chen <shanpeic@linux.alibaba.com>

commit 66567fcbaecac455caa1b13643155d686b51ce63 upstream.

When a cfs_rq sleeps and returns its quota, we delay for 5ms before
waking any throttled cfs_rqs to coalesce with other cfs_rqs going to
sleep, as this has to be done outside of the rq lock we hold.

The current code waits for 5ms without any sleeps, instead of waiting
for 5ms from the first sleep, which can delay the unthrottle more than
we want. Switch this around so that we can't push this forward forever.

This requires an extra flag rather than using hrtimer_active, since we
need to start a new timer if the current one is in the process of
finishing.
Signed-off-by: NBen Segall <bsegall@google.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
Acked-by: NPhil Auld <pauld@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/xm26a7euy6iq.fsf_-_@bsegall-linux.svl.corp.google.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NShanpei Chen <shanpeic@linux.alibaba.com>
Acked-by: NMichael Wang <yun.wang@linux.alibaba.com>

commit 4929a4e6faa0f13289a67cae98139e727f0d4a97 upstream.

The quota/period ratio is used to ensure a child task group won't get
more bandwidth than the parent task group, and is calculated as:

  normalized_cfs_quota() = [(quota_us << 20) / period_us]

If the quota/period ratio was changed during this scaling due to
precision loss, it will cause inconsistency between parent and child
task groups.

See below example:

A userspace container manager (kubelet) does three operations:

 1) Create a parent cgroup, set quota to 1,000us and period to 10,000us.
 2) Create a few children cgroups.
 3) Set quota to 1,000us and period to 10,000us on a child cgroup.

These operations are expected to succeed. However, if the scaling of
147/128 happens before step 3, quota and period of the parent cgroup
will be changed:

  new_quota: 1148437ns,   1148us
 new_period: 11484375ns, 11484us

And when step 3 comes in, the ratio of the child cgroup will be
104857, which will be larger than the parent cgroup ratio (104821),
and will fail.

Scaling them by a factor of 2 will fix the problem.
Tested-by: NPhil Auld <pauld@redhat.com>
Signed-off-by: NXuewei Zhang <xueweiz@google.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NPhil Auld <pauld@redhat.com>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Fixes: 2e8e19226398 ("sched/fair: Limit sched_cfs_period_timer() loop to avoid hard lockup")
Link: https://lkml.kernel.org/r/20191004001243.140897-1-xueweiz@google.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit 3f130a37c442d5c4d66531b240ebe9abfef426b5 ]

When load_balance() fails to move some load because of task affinity,
we end up increasing sd->balance_interval to delay the next periodic
balance in the hopes that next time we look, that annoying pinned
task(s) will be gone.

However, idle_balance() pays no attention to sd->balance_interval, yet
it will still lead to an increase in balance_interval in case of
pinned tasks.

If we're going through several newidle balances (e.g. we have a
periodic task), this can lead to a huge increase of the
balance_interval in a very small amount of time.

To prevent that, don't increase the balance interval when going
through a newidle balance.

This is a similar approach to what is done in commit 58b26c4c
("sched: Increment cache_nice_tries only on periodic lb"), where we
disregard newidle balance and rely on periodic balance for more stable
results.
Signed-off-by: NValentin Schneider <valentin.schneider@arm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dietmar.Eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: patrick.bellasi@arm.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1537974727-30788-2-git-send-email-valentin.schneider@arm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>

commit 763a9ec06c409dcde2a761aac4bb83ff3938e0b3 upstream.

Commit:

   de53fd7aedb1 ("sched/fair: Fix low cpu usage with high throttling by removing expiration of cpu-local slices")

introduced a few compilation warnings:

  kernel/sched/fair.c: In function '__refill_cfs_bandwidth_runtime':
  kernel/sched/fair.c:4365:6: warning: variable 'now' set but not used [-Wunused-but-set-variable]
  kernel/sched/fair.c: In function 'start_cfs_bandwidth':
  kernel/sched/fair.c:4992:6: warning: variable 'overrun' set but not used [-Wunused-but-set-variable]

Also, __refill_cfs_bandwidth_runtime() does no longer update the
expiration time, so fix the comments accordingly.
Signed-off-by: NQian Cai <cai@lca.pw>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NBen Segall <bsegall@google.com>
Reviewed-by: NDave Chiluk <chiluk+linux@indeed.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: pauld@redhat.com
Fixes: de53fd7aedb1 ("sched/fair: Fix low cpu usage with high throttling by removing expiration of cpu-local slices")
Link: https://lkml.kernel.org/r/1566326455-8038-1-git-send-email-cai@lca.pwSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

commit de53fd7aedb100f03e5d2231cfce0e4993282425 upstream.

It has been observed, that highly-threaded, non-cpu-bound applications
running under cpu.cfs_quota_us constraints can hit a high percentage of
periods throttled while simultaneously not consuming the allocated
amount of quota. This use case is typical of user-interactive non-cpu
bound applications, such as those running in kubernetes or mesos when
run on multiple cpu cores.

This has been root caused to cpu-local run queue being allocated per cpu
bandwidth slices, and then not fully using that slice within the period.
At which point the slice and quota expires. This expiration of unused
slice results in applications not being able to utilize the quota for
which they are allocated.

The non-expiration of per-cpu slices was recently fixed by
'commit 512ac999 ("sched/fair: Fix bandwidth timer clock drift
condition")'. Prior to that it appears that this had been broken since
at least 'commit 51f2176d ("sched/fair: Fix unlocked reads of some
cfs_b->quota/period")' which was introduced in v3.16-rc1 in 2014. That
added the following conditional which resulted in slices never being
expired.

if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
	/* extend local deadline, drift is bounded above by 2 ticks */
	cfs_rq->runtime_expires += TICK_NSEC;

Because this was broken for nearly 5 years, and has recently been fixed
and is now being noticed by many users running kubernetes
(https://github.com/kubernetes/kubernetes/issues/67577) it is my opinion
that the mechanisms around expiring runtime should be removed
altogether.

This allows quota already allocated to per-cpu run-queues to live longer
than the period boundary. This allows threads on runqueues that do not
use much CPU to continue to use their remaining slice over a longer
period of time than cpu.cfs_period_us. However, this helps prevent the
above condition of hitting throttling while also not fully utilizing
your cpu quota.

This theoretically allows a machine to use slightly more than its
allotted quota in some periods. This overflow would be bounded by the
remaining quota left on each per-cpu runqueueu. This is typically no
more than min_cfs_rq_runtime=1ms per cpu. For CPU bound tasks this will
change nothing, as they should theoretically fully utilize all of their
quota in each period. For user-interactive tasks as described above this
provides a much better user/application experience as their cpu
utilization will more closely match the amount they requested when they
hit throttling. This means that cpu limits no longer strictly apply per
period for non-cpu bound applications, but that they are still accurate
over longer timeframes.

This greatly improves performance of high-thread-count, non-cpu bound
applications with low cfs_quota_us allocation on high-core-count
machines. In the case of an artificial testcase (10ms/100ms of quota on
80 CPU machine), this commit resulted in almost 30x performance
improvement, while still maintaining correct cpu quota restrictions.
That testcase is available at https://github.com/indeedeng/fibtest.

Fixes: 512ac999 ("sched/fair: Fix bandwidth timer clock drift condition")
Signed-off-by: NDave Chiluk <chiluk+linux@indeed.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NPhil Auld <pauld@redhat.com>
Reviewed-by: NBen Segall <bsegall@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: John Hammond <jhammond@indeed.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kyle Anderson <kwa@yelp.com>
Cc: Gabriel Munos <gmunoz@netflix.com>
Cc: Peter Oskolkov <posk@posk.io>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Brendan Gregg <bgregg@netflix.com>
Link: https://lkml.kernel.org/r/1563900266-19734-2-git-send-email-chiluk+linux@indeed.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit a46d14eca7b75fffe35603aa8b81df654353d80f ]

Enabling WARN_DOUBLE_CLOCK in /sys/kernel/debug/sched_features causes
warning to fire in update_rq_clock. This seems to be caused by onlining
a new fair sched group not using the rq lock wrappers.

  [] rq->clock_update_flags & RQCF_UPDATED
  [] WARNING: CPU: 5 PID: 54385 at kernel/sched/core.c:210 update_rq_clock+0xec/0x150

  [] Call Trace:
  []  online_fair_sched_group+0x53/0x100
  []  cpu_cgroup_css_online+0x16/0x20
  []  online_css+0x1c/0x60
  []  cgroup_apply_control_enable+0x231/0x3b0
  []  cgroup_mkdir+0x41b/0x530
  []  kernfs_iop_mkdir+0x61/0xa0
  []  vfs_mkdir+0x108/0x1a0
  []  do_mkdirat+0x77/0xe0
  []  do_syscall_64+0x55/0x1d0
  []  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Using the wrappers in online_fair_sched_group instead of the raw locking
removes this warning.

[ tglx: Use rq_*lock_irq() ]
Signed-off-by: NPhil Auld <pauld@redhat.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20190801133749.11033-1-pauld@redhat.comSigned-off-by: NSasha Levin <sashal@kernel.org>

[ Upstream commit f6cad8df6b30a5d2bbbd2e698f74b4cafb9fb82b ]

The load_balance() has a dedicated mecanism to detect when an imbalance
is due to CPU affinity and must be handled at parent level. In this case,
the imbalance field of the parent's sched_group is set.

The description of sg_imbalanced() gives a typical example of two groups
of 4 CPUs each and 4 tasks each with a cpumask covering 1 CPU of the first
group and 3 CPUs of the second group. Something like:

	{ 0 1 2 3 } { 4 5 6 7 }
	        *     * * *

But the load_balance fails to fix this UC on my octo cores system
made of 2 clusters of quad cores.

Whereas the load_balance is able to detect that the imbalanced is due to
CPU affinity, it fails to fix it because the imbalance field is cleared
before letting parent level a chance to run. In fact, when the imbalance is
detected, the load_balance reruns without the CPU with pinned tasks. But
there is no other running tasks in the situation described above and
everything looks balanced this time so the imbalance field is immediately
cleared.

The imbalance field should not be cleared if there is no other task to move
when the imbalance is detected.
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1561996022-28829-1-git-send-email-vincent.guittot@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>

commit 5e2d2cc2588bd3307ce3937acbc2ed03c830a861 upstream.

do_sched_cfs_period_timer() will refill cfs_b runtime and call
distribute_cfs_runtime to unthrottle cfs_rq, sometimes cfs_b->runtime
will allocate all quota to one cfs_rq incorrectly, then other cfs_rqs
attached to this cfs_b can't get runtime and will be throttled.

We find that one throttled cfs_rq has non-negative
cfs_rq->runtime_remaining and cause an unexpetced cast from s64 to u64
in snippet:

  distribute_cfs_runtime() {
    runtime = -cfs_rq->runtime_remaining + 1;
  }

The runtime here will change to a large number and consume all
cfs_b->runtime in this cfs_b period.

According to Ben Segall, the throttled cfs_rq can have
account_cfs_rq_runtime called on it because it is throttled before
idle_balance, and the idle_balance calls update_rq_clock to add time
that is accounted to the task.

This commit prevents cfs_rq to be assgined new runtime if it has been
throttled until that distribute_cfs_runtime is called.
Signed-off-by: NLiangyan <liangyan.peng@linux.alibaba.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NValentin Schneider <valentin.schneider@arm.com>
Reviewed-by: NBen Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: shanpeic@linux.alibaba.com
Cc: stable@vger.kernel.org
Cc: xlpang@linux.alibaba.com
Fixes: d3d9dc33 ("sched: Throttle entities exceeding their allowed bandwidth")
Link: https://lkml.kernel.org/r/20190826121633.6538-1-liangyan.peng@linux.alibaba.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

commit cb361d8cdef69990f6b4504dc1fd9a594d983c97 upstream.

The old code used RCU annotations and accessors inconsistently for
->numa_group, which can lead to use-after-frees and NULL dereferences.

Let all accesses to ->numa_group use proper RCU helpers to prevent such
issues.
Signed-off-by: NJann Horn <jannh@google.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Fixes: 8c8a743c ("sched/numa: Use {cpu, pid} to create task groups for shared faults")
Link: https://lkml.kernel.org/r/20190716152047.14424-3-jannh@google.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 16d51a590a8ce3befb1308e0e7ab77f3b661af33 upstream.

When going through execve(), zero out the NUMA fault statistics instead of
freeing them.

During execve, the task is reachable through procfs and the scheduler. A
concurrent /proc/*/sched reader can read data from a freed ->numa_faults
allocation (confirmed by KASAN) and write it back to userspace.
I believe that it would also be possible for a use-after-free read to occur
through a race between a NUMA fault and execve(): task_numa_fault() can
lead to task_numa_compare(), which invokes task_weight() on the currently
running task of a different CPU.

Another way to fix this would be to make ->numa_faults RCU-managed or add
extra locking, but it seems easier to wipe the NUMA fault statistics on
execve.
Signed-off-by: NJann Horn <jannh@google.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Fixes: 82727018 ("sched/numa: Call task_numa_free() from do_execve()")
Link: https://lkml.kernel.org/r/20190716152047.14424-1-jannh@google.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

commit e9666d10a5677a494260d60d1fa0b73cc7646eb3 upstream.

Currently, CONFIG_JUMP_LABEL just means "I _want_ to use jump label".

The jump label is controlled by HAVE_JUMP_LABEL, which is defined
like this:

  #if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
  # define HAVE_JUMP_LABEL
  #endif

We can improve this by testing 'asm goto' support in Kconfig, then
make JUMP_LABEL depend on CC_HAS_ASM_GOTO.

Ugly #ifdef HAVE_JUMP_LABEL will go away, and CONFIG_JUMP_LABEL will
match to the real kernel capability.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Tested-by: NSedat Dilek <sedat.dilek@gmail.com>
[nc: Fix trivial conflicts in 4.19
     arch/xtensa/kernel/jump_label.c doesn't exist yet
     Ensured CC_HAVE_ASM_GOTO and HAVE_JUMP_LABEL were sufficiently
     eliminated]
Signed-off-by: NNathan Chancellor <natechancellor@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit 9b019acb72e4b5741d88e8936d6f200ed44b66b2 ]

The NOHZ idle balancer runs on the lowest idle CPU. This can
interfere with isolated CPUs, so confine it to HK_FLAG_MISC
housekeeping CPUs.

HK_FLAG_SCHED is not used for this because it is not set anywhere
at the moment. This could be folded into HK_FLAG_SCHED once that
option is fixed.

The problem was observed with increased jitter on an application
running on CPU0, caused by NOHZ idle load balancing being run on
CPU1 (an SMT sibling).
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190412042613.28930-1-npiggin@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>

commit a860fa7b96e1a1c974556327aa1aee852d434c21 upstream.

sched_clock_cpu() may not be consistent between CPUs. If a task
migrates to another CPU, then se.exec_start is set to that CPU's
rq_clock_task() by update_stats_curr_start(). Specifically, the new
value might be before the old value due to clock skew.

So then if in numa_get_avg_runtime() the expression:

  'now - p->last_task_numa_placement'

ends up as -1, then the divider '*period + 1' in task_numa_placement()
is 0 and things go bang. Similar to update_curr(), check if time goes
backwards to avoid this.

[ peterz: Wrote new changelog. ]
[ mingo: Tweaked the code comment. ]
Signed-off-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: cj.chengjian@huawei.com
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20190425080016.GX11158@hirez.programming.kicks-ass.netSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit 2e8e19226398db8265a8e675fcc0118b9e80c9e8 ]

With extremely short cfs_period_us setting on a parent task group with a large
number of children the for loop in sched_cfs_period_timer() can run until the
watchdog fires. There is no guarantee that the call to hrtimer_forward_now()
will ever return 0.  The large number of children can make
do_sched_cfs_period_timer() take longer than the period.

 NMI watchdog: Watchdog detected hard LOCKUP on cpu 24
 RIP: 0010:tg_nop+0x0/0x10
  <IRQ>
  walk_tg_tree_from+0x29/0xb0
  unthrottle_cfs_rq+0xe0/0x1a0
  distribute_cfs_runtime+0xd3/0xf0
  sched_cfs_period_timer+0xcb/0x160
  ? sched_cfs_slack_timer+0xd0/0xd0
  __hrtimer_run_queues+0xfb/0x270
  hrtimer_interrupt+0x122/0x270
  smp_apic_timer_interrupt+0x6a/0x140
  apic_timer_interrupt+0xf/0x20
  </IRQ>

To prevent this we add protection to the loop that detects when the loop has run
too many times and scales the period and quota up, proportionally, so that the timer
can complete before then next period expires.  This preserves the relative runtime
quota while preventing the hard lockup.

A warning is issued reporting this state and the new values.
Signed-off-by: NPhil Auld <pauld@redhat.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190319130005.25492-1-pauld@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>

commit 0e9f02450da07fc7b1346c8c32c771555173e397 upstream.

A NULL pointer dereference bug was reported on a distribution kernel but
the same issue should be present on mainline kernel. It occured on s390
but should not be arch-specific.  A partial oops looks like:

  Unable to handle kernel pointer dereference in virtual kernel address space
  ...
  Call Trace:
    ...
    try_to_wake_up+0xfc/0x450
    vhost_poll_wakeup+0x3a/0x50 [vhost]
    __wake_up_common+0xbc/0x178
    __wake_up_common_lock+0x9e/0x160
    __wake_up_sync_key+0x4e/0x60
    sock_def_readable+0x5e/0x98

The bug hits any time between 1 hour to 3 days. The dereference occurs
in update_cfs_rq_h_load when accumulating h_load. The problem is that
cfq_rq->h_load_next is not protected by any locking and can be updated
by parallel calls to task_h_load. Depending on the compiler, code may be
generated that re-reads cfq_rq->h_load_next after the check for NULL and
then oops when reading se->avg.load_avg. The dissassembly showed that it
was possible to reread h_load_next after the check for NULL.

While this does not appear to be an issue for later compilers, it's still
an accident if the correct code is generated. Full locking in this path
would have high overhead so this patch uses READ_ONCE to read h_load_next
only once and check for NULL before dereferencing. It was confirmed that
there were no further oops after 10 days of testing.

As Peter pointed out, it is also necessary to use WRITE_ONCE() to avoid any
potential problems with store tearing.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NValentin Schneider <valentin.schneider@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Fixes: 68520796 ("sched: Move h_load calculation to task_h_load()")
Link: https://lkml.kernel.org/r/20190319123610.nsivgf3mjbjjesxb@techsingularity.netSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

commit b284909abad48b07d3071a9fc9b5692b3e64914b upstream.

With the following commit:

  73d5e2b4 ("cpu/hotplug: detect SMT disabled by BIOS")

... the hotplug code attempted to detect when SMT was disabled by BIOS,
in which case it reported SMT as permanently disabled.  However, that
code broke a virt hotplug scenario, where the guest is booted with only
primary CPU threads, and a sibling is brought online later.

The problem is that there doesn't seem to be a way to reliably
distinguish between the HW "SMT disabled by BIOS" case and the virt
"sibling not yet brought online" case.  So the above-mentioned commit
was a bit misguided, as it permanently disabled SMT for both cases,
preventing future virt sibling hotplugs.

Going back and reviewing the original problems which were attempted to
be solved by that commit, when SMT was disabled in BIOS:

  1) /sys/devices/system/cpu/smt/control showed "on" instead of
     "notsupported"; and

  2) vmx_vm_init() was incorrectly showing the L1TF_MSG_SMT warning.

I'd propose that we instead consider #1 above to not actually be a
problem.  Because, at least in the virt case, it's possible that SMT
wasn't disabled by BIOS and a sibling thread could be brought online
later.  So it makes sense to just always default the smt control to "on"
to allow for that possibility (assuming cpuid indicates that the CPU
supports SMT).

The real problem is #2, which has a simple fix: change vmx_vm_init() to
query the actual current SMT state -- i.e., whether any siblings are
currently online -- instead of looking at the SMT "control" sysfs value.

So fix it by:

  a) reverting the original "fix" and its followup fix:

     73d5e2b4 ("cpu/hotplug: detect SMT disabled by BIOS")
     bc2d8d26 ("cpu/hotplug: Fix SMT supported evaluation")

     and

  b) changing vmx_vm_init() to query the actual current SMT state --
     instead of the sysfs control value -- to determine whether the L1TF
     warning is needed.  This also requires the 'sched_smt_present'
     variable to exported, instead of 'cpu_smt_control'.

Fixes: 73d5e2b4 ("cpu/hotplug: detect SMT disabled by BIOS")
Reported-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Joe Mario <jmario@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kvm@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/e3a85d585da28cc333ecbc1e78ee9216e6da9396.1548794349.git.jpoimboe@redhat.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

commit c40f7d74c741a907cfaeb73a7697081881c497d0 upstream.

Zhipeng Xie, Xie XiuQi and Sargun Dhillon reported lockups in the
scheduler under high loads, starting at around the v4.18 time frame,
and Zhipeng Xie tracked it down to bugs in the rq->leaf_cfs_rq_list
manipulation.

Do a (manual) revert of:

  a9e7f654 ("sched/fair: Fix O(nr_cgroups) in load balance path")

It turns out that the list_del_leaf_cfs_rq() introduced by this commit
is a surprising property that was not considered in followup commits
such as:

  9c2791f9 ("sched/fair: Fix hierarchical order in rq->leaf_cfs_rq_list")

As Vincent Guittot explains:

 "I think that there is a bigger problem with commit a9e7f654 and
  cfs_rq throttling:

  Let take the example of the following topology TG2 --> TG1 --> root:

   1) The 1st time a task is enqueued, we will add TG2 cfs_rq then TG1
      cfs_rq to leaf_cfs_rq_list and we are sure to do the whole branch in
      one path because it has never been used and can't be throttled so
      tmp_alone_branch will point to leaf_cfs_rq_list at the end.

   2) Then TG1 is throttled

   3) and we add TG3 as a new child of TG1.

   4) The 1st enqueue of a task on TG3 will add TG3 cfs_rq just before TG1
      cfs_rq and tmp_alone_branch will stay  on rq->leaf_cfs_rq_list.

  With commit a9e7f654, we can del a cfs_rq from rq->leaf_cfs_rq_list.
  So if the load of TG1 cfs_rq becomes NULL before step 2) above, TG1
  cfs_rq is removed from the list.
  Then at step 4), TG3 cfs_rq is added at the beginning of rq->leaf_cfs_rq_list
  but tmp_alone_branch still points to TG3 cfs_rq because its throttled
  parent can't be enqueued when the lock is released.
  tmp_alone_branch doesn't point to rq->leaf_cfs_rq_list whereas it should.

  So if TG3 cfs_rq is removed or destroyed before tmp_alone_branch
  points on another TG cfs_rq, the next TG cfs_rq that will be added,
  will be linked outside rq->leaf_cfs_rq_list - which is bad.

  In addition, we can break the ordering of the cfs_rq in
  rq->leaf_cfs_rq_list but this ordering is used to update and
  propagate the update from leaf down to root."

Instead of trying to work through all these cases and trying to reproduce
the very high loads that produced the lockup to begin with, simplify
the code temporarily by reverting a9e7f654 - which change was clearly
not thought through completely.

This (hopefully) gives us a kernel that doesn't lock up so people
can continue to enjoy their holidays without worrying about regressions. ;-)

[ mingo: Wrote changelog, fixed weird spelling in code comment while at it. ]
Analyzed-by: NXie XiuQi <xiexiuqi@huawei.com>
Analyzed-by: NVincent Guittot <vincent.guittot@linaro.org>
Reported-by: NZhipeng Xie <xiezhipeng1@huawei.com>
Reported-by: NSargun Dhillon <sargun@sargun.me>
Reported-by: NXie XiuQi <xiexiuqi@huawei.com>
Tested-by: NZhipeng Xie <xiezhipeng1@huawei.com>
Tested-by: NSargun Dhillon <sargun@sargun.me>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: NVincent Guittot <vincent.guittot@linaro.org>
Cc: <stable@vger.kernel.org> # v4.13+
Cc: Bin Li <huawei.libin@huawei.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: a9e7f654 ("sched/fair: Fix O(nr_cgroups) in load balance path")
Link: http://lkml.kernel.org/r/1545879866-27809-1-git-send-email-xiexiuqi@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 11d4afd4ff667f9b6178ee8c142c36cb78bd84db upstream.

Create a config for enabling irq load tracking in the scheduler.
irq load tracking is useful only when irq or paravirtual time is
accounted but it's only possible with SMP for now.

Also use __maybe_unused to remove the compilation warning in
update_rq_clock_task() that has been introduced by:

  2e62c474 ("sched/fair: Remove #ifdefs from scale_rt_capacity()")
Suggested-by: NIngo Molnar <mingo@redhat.com>
Reported-by: NDou Liyang <douly.fnst@cn.fujitsu.com>
Reported-by: NMiguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bp@alien8.de
Cc: dou_liyang@163.com
Fixes: 2e62c474 ("sched/fair: Remove #ifdefs from scale_rt_capacity()")
Link: http://lkml.kernel.org/r/1537867062-27285-1-git-send-email-vincent.guittot@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>

[ Upstream commit c469933e ]

A ~10% regression has been reported for UnixBench's execl throughput
test by Aaron Lu and Ye Xiaolong:

  https://lkml.org/lkml/2018/10/30/765

That test is pretty simple, it does a "recursive" execve() syscall on the
same binary. Starting from the syscall, this sequence is possible:

   do_execve()
     do_execveat_common()
       __do_execve_file()
         sched_exec()
           select_task_rq_fair()          <==| Task already enqueued
             find_idlest_cpu()
               find_idlest_group()
                 capacity_spare_wake()    <==| Functions not called from
		   cpu_util_wake()           | the wakeup path

which means we can end up calling cpu_util_wake() not only from the
"wakeup path", as its name would suggest. Indeed, the task doing an
execve() syscall is already enqueued on the CPU we want to get the
cpu_util_wake() for.

The estimated utilization for a CPU computed in cpu_util_wake() was
written under the assumption that function can be called only from the
wakeup path. If instead the task is already enqueued, we end up with a
utilization which does not remove the current task's contribution from
the estimated utilization of the CPU.
This will wrongly assume a reduced spare capacity on the current CPU and
increase the chances to migrate the task on execve.

The regression is tracked down to:

 commit d519329f ("sched/fair: Update util_est only on util_avg updates")

because in that patch we turn on by default the UTIL_EST sched feature.
However, the real issue is introduced by:

 commit f9be3e59 ("sched/fair: Use util_est in LB and WU paths")

Let's fix this by ensuring to always discount the task estimated
utilization from the CPU's estimated utilization when the task is also
the current one. The same benchmark of the bug report, executed on a
dual socket 40 CPUs Intel(R) Xeon(R) CPU E5-2690 v2 @ 3.00GHz machine,
reports these "Execl Throughput" figures (higher the better):

   mainline     : 48136.5 lps
   mainline+fix : 55376.5 lps

which correspond to a 15% speedup.

Moreover, since {cpu_util,capacity_spare}_wake() are not really only
used from the wakeup path, let's remove this ambiguity by using a better
matching name: {cpu_util,capacity_spare}_without().

Since we are at that, let's also improve the existing documentation.
Reported-by: NAaron Lu <aaron.lu@intel.com>
Reported-by: NYe Xiaolong <xiaolong.ye@intel.com>
Tested-by: NAaron Lu <aaron.lu@intel.com>
Signed-off-by: NPatrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Perret <quentin.perret@arm.com>
Cc: Steve Muckle <smuckle@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Todd Kjos <tkjos@google.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Fixes: f9be3e59 (sched/fair: Use util_est in LB and WU paths)
Link: https://lore.kernel.org/lkml/20181025093100.GB13236@e110439-lin/Signed-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>

The comment and the code around the update_min_vruntime() call in
dequeue_entity() are not in agreement.

From commit:

  b60205c7 ("sched/fair: Fix min_vruntime tracking")

I think that we want to update min_vruntime when a task is sleeping/migrating.
So, the check is inverted there - fix it.
Signed-off-by: NSong Muchun <smuchun@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: b60205c7 ("sched/fair: Fix min_vruntime tracking")
Link: http://lkml.kernel.org/r/20181014112612.2614-1-smuchun@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

With a very low cpu.cfs_quota_us setting, such as the minimum of 1000,
distribute_cfs_runtime may not empty the throttled_list before it runs
out of runtime to distribute. In that case, due to the change from
c06f04c7 to put throttled entries at the head of the list, later entries
on the list will starve.  Essentially, the same X processes will get pulled
off the list, given CPU time and then, when expired, get put back on the
head of the list where distribute_cfs_runtime will give runtime to the same
set of processes leaving the rest.

Fix the issue by setting a bit in struct cfs_bandwidth when
distribute_cfs_runtime is running, so that the code in throttle_cfs_rq can
decide to put the throttled entry on the tail or the head of the list.  The
bit is set/cleared by the callers of distribute_cfs_runtime while they hold
cfs_bandwidth->lock.

This is easy to reproduce with a handful of CPU consumers. I use 'crash' on
the live system. In some cases you can simply look at the throttled list and
see the later entries are not changing:

  crash> list cfs_rq.throttled_list -H 0xffff90b54f6ade40 -s cfs_rq.runtime_remaining | paste - - | awk '{print $1"  "$4}' | pr -t -n3
    1     ffff90b56cb2d200  -976050
    2     ffff90b56cb2cc00  -484925
    3     ffff90b56cb2bc00  -658814
    4     ffff90b56cb2ba00  -275365
    5     ffff90b166a45600  -135138
    6     ffff90b56cb2da00  -282505
    7     ffff90b56cb2e000  -148065
    8     ffff90b56cb2fa00  -872591
    9     ffff90b56cb2c000  -84687
   10     ffff90b56cb2f000  -87237
   11     ffff90b166a40a00  -164582

  crash> list cfs_rq.throttled_list -H 0xffff90b54f6ade40 -s cfs_rq.runtime_remaining | paste - - | awk '{print $1"  "$4}' | pr -t -n3
    1     ffff90b56cb2d200  -994147
    2     ffff90b56cb2cc00  -306051
    3     ffff90b56cb2bc00  -961321
    4     ffff90b56cb2ba00  -24490
    5     ffff90b166a45600  -135138
    6     ffff90b56cb2da00  -282505
    7     ffff90b56cb2e000  -148065
    8     ffff90b56cb2fa00  -872591
    9     ffff90b56cb2c000  -84687
   10     ffff90b56cb2f000  -87237
   11     ffff90b166a40a00  -164582

Sometimes it is easier to see by finding a process getting starved and looking
at the sched_info:

  crash> task ffff8eb765994500 sched_info
  PID: 7800   TASK: ffff8eb765994500  CPU: 16  COMMAND: "cputest"
    sched_info = {
      pcount = 8,
      run_delay = 697094208,
      last_arrival = 240260125039,
      last_queued = 240260327513
    },
  crash> task ffff8eb765994500 sched_info
  PID: 7800   TASK: ffff8eb765994500  CPU: 16  COMMAND: "cputest"
    sched_info = {
      pcount = 8,
      run_delay = 697094208,
      last_arrival = 240260125039,
      last_queued = 240260327513
    },
Signed-off-by: NPhil Auld <pauld@redhat.com>
Reviewed-by: NBen Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: c06f04c7 ("sched: Fix potential near-infinite distribute_cfs_runtime() loop")
Link: http://lkml.kernel.org/r/20181008143639.GA4019@pauld.bos.csbSigned-off-by: NIngo Molnar <mingo@kernel.org>

Automatic NUMA Balancing uses a multi-stage pass to decide whether a page
should migrate to a local node. This filter avoids excessive ping-ponging
if a page is shared or used by threads that migrate cross-node frequently.

Threads inherit both page tables and the preferred node ID from the
parent. This means that threads can trigger hinting faults earlier than
a new task which delays scanning for a number of seconds. As it can be
load balanced very early in its lifetime there can be an unnecessary delay
before it starts migrating thread-local data. This patch migrates private
pages faster early in the lifetime of a thread using the sequence counter
as an identifier of new tasks.

With this patch applied, STREAM performance is the same as 4.17 even though
processes are not spread cross-node prematurely. Other workloads showed
a mix of minor gains and losses. This is somewhat expected most workloads
are not very sensitive to the starting conditions of a process.

                         4.19.0-rc5             4.19.0-rc5                 4.17.0
                         numab-v1r1       fastmigrate-v1r1                vanilla
MB/sec copy     43298.52 (   0.00%)    47335.46 (   9.32%)    47219.24 (   9.06%)
MB/sec scale    30115.06 (   0.00%)    32568.12 (   8.15%)    32527.56 (   8.01%)
MB/sec add      32825.12 (   0.00%)    36078.94 (   9.91%)    35928.02 (   9.45%)
MB/sec triad    32549.52 (   0.00%)    35935.94 (  10.40%)    35969.88 (  10.51%)
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Reviewed-by: NRik van Riel <riel@surriel.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jirka Hladky <jhladky@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20181001100525.29789-3-mgorman@techsingularity.netSigned-off-by: NIngo Molnar <mingo@kernel.org>

If NUMA improvement from the task migration is going to be very
minimal, then avoid task migration.

Specjbb2005 results (8 warehouses)
Higher bops are better

2 Socket - 2  Node Haswell - X86
JVMS  Prev    Current  %Change
4     198512  205910   3.72673
1     313559  318491   1.57291

2 Socket - 4 Node Power8 - PowerNV
JVMS  Prev     Current  %Change
8     74761.9  74935.9  0.232739
1     214874   226796   5.54837

2 Socket - 2  Node Power9 - PowerNV
JVMS  Prev    Current  %Change
4     180536  189780   5.12031
1     210281  205695   -2.18089

4 Socket - 4  Node Power7 - PowerVM
JVMS  Prev     Current  %Change
8     56511.4  60370    6.828
1     104899   108100   3.05151

1/7 cases is regressing, if we look at events migrate_pages seem
to vary the most especially in the regressing case. Also some
amount of variance is expected between different runs of
Specjbb2005.

Some events stats before and after applying the patch.

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        13,818,546      13,801,554
migrations                1,149,960       1,151,541
faults                    385,583         433,246
cache-misses              55,259,546,768  55,168,691,835
sched:sched_move_numa     2,257           2,551
sched:sched_stick_numa    9               24
sched:sched_swap_numa     512             904
migrate:mm_migrate_pages  2,225           1,571

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        72692   113682
numa_hint_faults_local  62270   102163
numa_hit                238762  240181
numa_huge_pte_updates   48      36
numa_interleave         75      64
numa_local              238676  240103
numa_other              86      78
numa_pages_migrated     2225    1564
numa_pte_updates        98557   134080

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        3,173,490       3,079,150
migrations                36,966          31,455
faults                    108,776         99,081
cache-misses              12,200,075,320  11,588,126,740
sched:sched_move_numa     1,264           1
sched:sched_stick_numa    0               0
sched:sched_swap_numa     0               0
migrate:mm_migrate_pages  899             36

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        21109   430
numa_hint_faults_local  17120   77
numa_hit                72934   71277
numa_huge_pte_updates   42      0
numa_interleave         33      22
numa_local              72866   71218
numa_other              68      59
numa_pages_migrated     915     23
numa_pte_updates        42326   0

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before       After
cs                        8,312,022    8,707,565
migrations                231,705      171,342
faults                    310,242      310,820
cache-misses              402,324,573  136,115,400
sched:sched_move_numa     193          215
sched:sched_stick_numa    0            6
sched:sched_swap_numa     3            24
migrate:mm_migrate_pages  93           162

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        11838   8985
numa_hint_faults_local  11216   8154
numa_hit                90689   93819
numa_huge_pte_updates   0       0
numa_interleave         1579    882
numa_local              89634   93496
numa_other              1055    323
numa_pages_migrated     92      169
numa_pte_updates        12109   9217

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before      After
cs                        2,170,481   2,152,072
migrations                10,126      10,704
faults                    160,962     164,376
cache-misses              10,834,845  3,818,437
sched:sched_move_numa     10          16
sched:sched_stick_numa    0           0
sched:sched_swap_numa     0           7
migrate:mm_migrate_pages  2           199

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        403     2248
numa_hint_faults_local  358     1666
numa_hit                25898   25704
numa_huge_pte_updates   0       0
numa_interleave         207     200
numa_local              25860   25679
numa_other              38      25
numa_pages_migrated     2       197
numa_pte_updates        400     2234

perf stats 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before           After
cs                        110,339,633      93,330,595
migrations                4,139,812        4,122,061
faults                    863,622          865,979
cache-misses              231,838,045,660  225,395,083,479
sched:sched_move_numa     2,196            2,372
sched:sched_stick_numa    33               24
sched:sched_swap_numa     544              769
migrate:mm_migrate_pages  2,469            1,677

vmstat 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        85748   91638
numa_hint_faults_local  66831   78096
numa_hit                242213  242225
numa_huge_pte_updates   0       0
numa_interleave         0       2
numa_local              242211  242219
numa_other              2       6
numa_pages_migrated     2376    1515
numa_pte_updates        86233   92274

perf stats 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before          After
cs                        59,331,057      51,487,271
migrations                552,019         537,170
faults                    266,586         256,921
cache-misses              73,796,312,990  70,073,831,187
sched:sched_move_numa     981             576
sched:sched_stick_numa    54              24
sched:sched_swap_numa     286             327
migrate:mm_migrate_pages  713             726

vmstat 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        14807   12000
numa_hint_faults_local  5738    5024
numa_hit                36230   36470
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              36228   36465
numa_other              2       5
numa_pages_migrated     703     726
numa_pte_updates        14742   11930
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jirka Hladky <jhladky@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1537552141-27815-7-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

migrate_task_rq_fair() resets the scan rate for NUMA balancing on every
cross-node migration. In the event of excessive load balancing due to
saturation, this may result in the scan rate being pegged at maximum and
further overloading the machine.

This patch only resets the scan if NUMA balancing is active, a preferred
node has been selected and the task is being migrated from the preferred
node as these are the most harmful. For example, a migration to the preferred
node does not justify a faster scan rate. Similarly, a migration between two
nodes that are not preferred is probably bouncing due to over-saturation of
the machine.  In that case, scanning faster and trapping more NUMA faults
will further overload the machine.

Specjbb2005 results (8 warehouses)
Higher bops are better

2 Socket - 2  Node Haswell - X86
JVMS  Prev    Current  %Change
4     203370  205332   0.964744
1     328431  319785   -2.63252

2 Socket - 4 Node Power8 - PowerNV
JVMS  Prev    Current  %Change
1     206070  206585   0.249915

2 Socket - 2  Node Power9 - PowerNV
JVMS  Prev    Current  %Change
4     188386  189162   0.41192
1     201566  213760   6.04963

4 Socket - 4  Node Power7 - PowerVM
JVMS  Prev     Current  %Change
8     59157.4  58736.8  -0.710985
1     105495   105419   -0.0720413

Some events stats before and after applying the patch.

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        13,825,492      14,285,708
migrations                1,152,509       1,180,621
faults                    371,948         339,114
cache-misses              55,654,206,041  55,205,631,894
sched:sched_move_numa     1,856           843
sched:sched_stick_numa    4               6
sched:sched_swap_numa     428             219
migrate:mm_migrate_pages  898             365

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        57146   26907
numa_hint_faults_local  51612   24279
numa_hit                238164  239771
numa_huge_pte_updates   16      0
numa_interleave         63      68
numa_local              238085  239688
numa_other              79      83
numa_pages_migrated     883     363
numa_pte_updates        67540   27415

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        3,288,525       3,202,779
migrations                38,652          37,186
faults                    111,678         106,076
cache-misses              12,111,197,376  12,024,873,744
sched:sched_move_numa     900             931
sched:sched_stick_numa    0               0
sched:sched_swap_numa     5               1
migrate:mm_migrate_pages  714             637

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        18572   17409
numa_hint_faults_local  14850   14367
numa_hit                73197   73953
numa_huge_pte_updates   11      20
numa_interleave         25      25
numa_local              73138   73892
numa_other              59      61
numa_pages_migrated     712     668
numa_pte_updates        24021   27276

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before       After
cs                        8,451,543    8,474,013
migrations                202,804      254,934
faults                    310,024      320,506
cache-misses              253,522,507  110,580,458
sched:sched_move_numa     213          725
sched:sched_stick_numa    0            0
sched:sched_swap_numa     2            7
migrate:mm_migrate_pages  88           145

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        11830   22797
numa_hint_faults_local  11301   21539
numa_hit                90038   89308
numa_huge_pte_updates   0       0
numa_interleave         855     865
numa_local              89796   88955
numa_other              242     353
numa_pages_migrated     88      149
numa_pte_updates        12039   22930

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before     After
cs                        2,049,153  2,195,628
migrations                11,405     11,179
faults                    162,309    149,656
cache-misses              7,203,343  8,117,515
sched:sched_move_numa     22         49
sched:sched_stick_numa    0          0
sched:sched_swap_numa     0          0
migrate:mm_migrate_pages  1          5

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        1693    3577
numa_hint_faults_local  1669    3476
numa_hit                25177   26142
numa_huge_pte_updates   0       0
numa_interleave         194     358
numa_local              24993   26042
numa_other              184     100
numa_pages_migrated     1       5
numa_pte_updates        1577    3587

perf stats 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before           After
cs                        94,515,937       100,602,296
migrations                4,203,554        4,135,630
faults                    832,697          789,256
cache-misses              226,248,698,331  226,160,621,058
sched:sched_move_numa     1,730            1,366
sched:sched_stick_numa    14               16
sched:sched_swap_numa     432              374
migrate:mm_migrate_pages  1,398            1,350

vmstat 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        80079   47857
numa_hint_faults_local  68620   39768
numa_hit                241187  240165
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              241186  240165
numa_other              1       0
numa_pages_migrated     1347    1224
numa_pte_updates        80729   48354

perf stats 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before          After
cs                        63,704,961      58,515,496
migrations                573,404         564,845
faults                    230,878         245,807
cache-misses              76,568,222,781  73,603,757,976
sched:sched_move_numa     509             996
sched:sched_stick_numa    31              10
sched:sched_swap_numa     182             193
migrate:mm_migrate_pages  541             646

vmstat 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        8501    13422
numa_hint_faults_local  2960    5619
numa_hit                35526   36118
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              35526   36116
numa_other              0       2
numa_pages_migrated     539     616
numa_pte_updates        8433    13374
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jirka Hladky <jhladky@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1537552141-27815-5-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Currently task scan rate is reset when NUMA balancer migrates the task
to a different node. If NUMA balancer initiates a swap, reset is only
applicable to the task that initiates the swap. Similarly no scan rate
reset is done if the task is migrated across nodes by traditional load
balancer.

Instead move the scan reset to the migrate_task_rq. This ensures the
task moved out of its preferred node, either gets back to its preferred
node quickly or finds a new preferred node. Doing so, would be fair to
all tasks migrating across nodes.

Specjbb2005 results (8 warehouses)
Higher bops are better

2 Socket - 2  Node Haswell - X86
JVMS  Prev    Current  %Change
4     200668  203370   1.3465
1     321791  328431   2.06345

2 Socket - 4 Node Power8 - PowerNV
JVMS  Prev    Current  %Change
1     204848  206070   0.59654

2 Socket - 2  Node Power9 - PowerNV
JVMS  Prev    Current  %Change
4     188098  188386   0.153112
1     200351  201566   0.606436

4 Socket - 4  Node Power7 - PowerVM
JVMS  Prev     Current  %Change
8     58145.9  59157.4  1.73959
1     103798   105495   1.63491

Some events stats before and after applying the patch.

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        13,912,183      13,825,492
migrations                1,155,931       1,152,509
faults                    367,139         371,948
cache-misses              54,240,196,814  55,654,206,041
sched:sched_move_numa     1,571           1,856
sched:sched_stick_numa    9               4
sched:sched_swap_numa     463             428
migrate:mm_migrate_pages  703             898

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        50155   57146
numa_hint_faults_local  45264   51612
numa_hit                239652  238164
numa_huge_pte_updates   36      16
numa_interleave         68      63
numa_local              239576  238085
numa_other              76      79
numa_pages_migrated     680     883
numa_pte_updates        71146   67540

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        3,156,720       3,288,525
migrations                30,354          38,652
faults                    97,261          111,678
cache-misses              12,400,026,826  12,111,197,376
sched:sched_move_numa     4               900
sched:sched_stick_numa    0               0
sched:sched_swap_numa     1               5
migrate:mm_migrate_pages  20              714

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        272     18572
numa_hint_faults_local  186     14850
numa_hit                71362   73197
numa_huge_pte_updates   0       11
numa_interleave         23      25
numa_local              71299   73138
numa_other              63      59
numa_pages_migrated     2       712
numa_pte_updates        0       24021

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before       After
cs                        8,606,824    8,451,543
migrations                155,352      202,804
faults                    301,409      310,024
cache-misses              157,759,224  253,522,507
sched:sched_move_numa     168          213
sched:sched_stick_numa    0            0
sched:sched_swap_numa     3            2
migrate:mm_migrate_pages  125          88

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        4650    11830
numa_hint_faults_local  3946    11301
numa_hit                90489   90038
numa_huge_pte_updates   0       0
numa_interleave         892     855
numa_local              90034   89796
numa_other              455     242
numa_pages_migrated     124     88
numa_pte_updates        4818    12039

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before     After
cs                        2,113,167  2,049,153
migrations                10,533     11,405
faults                    142,727    162,309
cache-misses              5,594,192  7,203,343
sched:sched_move_numa     10         22
sched:sched_stick_numa    0          0
sched:sched_swap_numa     0          0
migrate:mm_migrate_pages  6          1

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        744     1693
numa_hint_faults_local  584     1669
numa_hit                25551   25177
numa_huge_pte_updates   0       0
numa_interleave         263     194
numa_local              25302   24993
numa_other              249     184
numa_pages_migrated     6       1
numa_pte_updates        744     1577

perf stats 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before           After
cs                        101,227,352      94,515,937
migrations                4,151,829        4,203,554
faults                    745,233          832,697
cache-misses              224,669,561,766  226,248,698,331
sched:sched_move_numa     617              1,730
sched:sched_stick_numa    2                14
sched:sched_swap_numa     187              432
migrate:mm_migrate_pages  316              1,398

vmstat 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        24195   80079
numa_hint_faults_local  21639   68620
numa_hit                238331  241187
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              238331  241186
numa_other              0       1
numa_pages_migrated     204     1347
numa_pte_updates        24561   80729

perf stats 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before          After
cs                        62,738,978      63,704,961
migrations                562,702         573,404
faults                    228,465         230,878
cache-misses              75,778,067,952  76,568,222,781
sched:sched_move_numa     648             509
sched:sched_stick_numa    13              31
sched:sched_swap_numa     137             182
migrate:mm_migrate_pages  733             541

vmstat 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        10281   8501
numa_hint_faults_local  3242    2960
numa_hit                36338   35526
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              36338   35526
numa_other              0       0
numa_pages_migrated     706     539
numa_pte_updates        10176   8433
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jirka Hladky <jhladky@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1537552141-27815-4-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This additional parameter (new_cpu) is used later for identifying if
task migration is across nodes.

No functional change.

Specjbb2005 results (8 warehouses)
Higher bops are better

2 Socket - 2  Node Haswell - X86
JVMS  Prev    Current  %Change
4     203353  200668   -1.32036
1     328205  321791   -1.95427

2 Socket - 4 Node Power8 - PowerNV
JVMS  Prev    Current  %Change
1     214384  204848   -4.44809

2 Socket - 2  Node Power9 - PowerNV
JVMS  Prev    Current  %Change
4     188553  188098   -0.241311
1     196273  200351   2.07772

4 Socket - 4  Node Power7 - PowerVM
JVMS  Prev     Current  %Change
8     57581.2  58145.9  0.980702
1     103468   103798   0.318939

Brings out the variance between different specjbb2005 runs.

Some events stats before and after applying the patch.

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        13,941,377      13,912,183
migrations                1,157,323       1,155,931
faults                    382,175         367,139
cache-misses              54,993,823,500  54,240,196,814
sched:sched_move_numa     2,005           1,571
sched:sched_stick_numa    14              9
sched:sched_swap_numa     529             463
migrate:mm_migrate_pages  1,573           703

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        67099   50155
numa_hint_faults_local  58456   45264
numa_hit                240416  239652
numa_huge_pte_updates   18      36
numa_interleave         65      68
numa_local              240339  239576
numa_other              77      76
numa_pages_migrated     1574    680
numa_pte_updates        77182   71146

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        3,176,453       3,156,720
migrations                30,238          30,354
faults                    87,869          97,261
cache-misses              12,544,479,391  12,400,026,826
sched:sched_move_numa     23              4
sched:sched_stick_numa    0               0
sched:sched_swap_numa     6               1
migrate:mm_migrate_pages  10              20

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        236     272
numa_hint_faults_local  201     186
numa_hit                72293   71362
numa_huge_pte_updates   0       0
numa_interleave         26      23
numa_local              72233   71299
numa_other              60      63
numa_pages_migrated     8       2
numa_pte_updates        0       0

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before       After
cs                        8,478,820    8,606,824
migrations                171,323      155,352
faults                    307,499      301,409
cache-misses              240,353,599  157,759,224
sched:sched_move_numa     214          168
sched:sched_stick_numa    0            0
sched:sched_swap_numa     4            3
migrate:mm_migrate_pages  89           125

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        5301    4650
numa_hint_faults_local  4745    3946
numa_hit                92943   90489
numa_huge_pte_updates   0       0
numa_interleave         899     892
numa_local              92345   90034
numa_other              598     455
numa_pages_migrated     88      124
numa_pte_updates        5505    4818

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before      After
cs                        2,066,172   2,113,167
migrations                11,076      10,533
faults                    149,544     142,727
cache-misses              10,398,067  5,594,192
sched:sched_move_numa     43          10
sched:sched_stick_numa    0           0
sched:sched_swap_numa     0           0
migrate:mm_migrate_pages  6           6

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        3552    744
numa_hint_faults_local  3347    584
numa_hit                25611   25551
numa_huge_pte_updates   0       0
numa_interleave         213     263
numa_local              25583   25302
numa_other              28      249
numa_pages_migrated     6       6
numa_pte_updates        3535    744

perf stats 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before           After
cs                        99,358,136       101,227,352
migrations                4,041,607        4,151,829
faults                    749,653          745,233
cache-misses              225,562,543,251  224,669,561,766
sched:sched_move_numa     771              617
sched:sched_stick_numa    14               2
sched:sched_swap_numa     204              187
migrate:mm_migrate_pages  1,180            316

vmstat 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        27409   24195
numa_hint_faults_local  20677   21639
numa_hit                239988  238331
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              239983  238331
numa_other              5       0
numa_pages_migrated     1016    204
numa_pte_updates        27916   24561

perf stats 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before          After
cs                        60,899,307      62,738,978
migrations                544,668         562,702
faults                    270,834         228,465
cache-misses              74,543,455,635  75,778,067,952
sched:sched_move_numa     735             648
sched:sched_stick_numa    25              13
sched:sched_swap_numa     174             137
migrate:mm_migrate_pages  816             733

vmstat 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        11059   10281
numa_hint_faults_local  4733    3242
numa_hit                41384   36338
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              41383   36338
numa_other              1       0
numa_pages_migrated     815     706
numa_pte_updates        11323   10176
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jirka Hladky <jhladky@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1537552141-27815-3-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Task migration under NUMA balancing can happen in parallel. More than
one task might choose to migrate to the same CPU at the same time. This
can result in:

- During task swap, choosing a task that was not part of the evaluation.
- During task swap, task which just got moved into its preferred node,
  moving to a completely different node.
- During task swap, task failing to move to the preferred node, will have
  to wait an extra interval for the next migrate opportunity.
- During task movement, multiple task movements can cause load imbalance.

This problem is more likely if there are more cores per node or more
nodes in the system.

Use a per run-queue variable to check if NUMA-balance is active on the
run-queue.

Specjbb2005 results (8 warehouses)
Higher bops are better

2 Socket - 2  Node Haswell - X86
JVMS  Prev    Current  %Change
4     200194  203353   1.57797
1     311331  328205   5.41995

2 Socket - 4 Node Power8 - PowerNV
JVMS  Prev    Current  %Change
1     197654  214384   8.46429

2 Socket - 2  Node Power9 - PowerNV
JVMS  Prev    Current  %Change
4     192605  188553   -2.10379
1     213402  196273   -8.02664

4 Socket - 4  Node Power7 - PowerVM
JVMS  Prev     Current  %Change
8     52227.1  57581.2  10.2516
1     102529   103468   0.915838

There is a regression on power 9 box. If we look at the details,
that box has a sudden jump in cache-misses with this patch.
All other parameters seem to be pointing towards NUMA
consolidation.

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        13,345,784      13,941,377
migrations                1,127,820       1,157,323
faults                    374,736         382,175
cache-misses              55,132,054,603  54,993,823,500
sched:sched_move_numa     1,923           2,005
sched:sched_stick_numa    52              14
sched:sched_swap_numa     595             529
migrate:mm_migrate_pages  1,932           1,573

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        60605   67099
numa_hint_faults_local  51804   58456
numa_hit                239945  240416
numa_huge_pte_updates   14      18
numa_interleave         60      65
numa_local              239865  240339
numa_other              80      77
numa_pages_migrated     1931    1574
numa_pte_updates        67823   77182

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                     Before          After
cs                        3,016,467       3,176,453
migrations                37,326          30,238
faults                    115,342         87,869
cache-misses              11,692,155,554  12,544,479,391
sched:sched_move_numa     965             23
sched:sched_stick_numa    8               0
sched:sched_swap_numa     35              6
migrate:mm_migrate_pages  1,168           10

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Haswell - X86
Event                   Before  After
numa_hint_faults        16286   236
numa_hint_faults_local  11863   201
numa_hit                112482  72293
numa_huge_pte_updates   33      0
numa_interleave         20      26
numa_local              112419  72233
numa_other              63      60
numa_pages_migrated     1144    8
numa_pte_updates        32859   0

perf stats 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before       After
cs                        8,629,724    8,478,820
migrations                221,052      171,323
faults                    308,661      307,499
cache-misses              135,574,913  240,353,599
sched:sched_move_numa     147          214
sched:sched_stick_numa    0            0
sched:sched_swap_numa     2            4
migrate:mm_migrate_pages  64           89

vmstat 8th warehouse Multi JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        11481   5301
numa_hint_faults_local  10968   4745
numa_hit                89773   92943
numa_huge_pte_updates   0       0
numa_interleave         1116    899
numa_local              89220   92345
numa_other              553     598
numa_pages_migrated     62      88
numa_pte_updates        11694   5505

perf stats 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                     Before     After
cs                        2,272,887  2,066,172
migrations                12,206     11,076
faults                    163,704    149,544
cache-misses              4,801,186  10,398,067
sched:sched_move_numa     44         43
sched:sched_stick_numa    0          0
sched:sched_swap_numa     0          0
migrate:mm_migrate_pages  17         6

vmstat 8th warehouse Single JVM 2 Socket - 2  Node Power9 - PowerNV
Event                   Before  After
numa_hint_faults        2261    3552
numa_hint_faults_local  1993    3347
numa_hit                25726   25611
numa_huge_pte_updates   0       0
numa_interleave         239     213
numa_local              25498   25583
numa_other              228     28
numa_pages_migrated     17      6
numa_pte_updates        2266    3535

perf stats 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before           After
cs                        117,980,962      99,358,136
migrations                3,950,220        4,041,607
faults                    736,979          749,653
cache-misses              224,976,072,879  225,562,543,251
sched:sched_move_numa     504              771
sched:sched_stick_numa    50               14
sched:sched_swap_numa     239              204
migrate:mm_migrate_pages  1,260            1,180

vmstat 8th warehouse Multi JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        18293   27409
numa_hint_faults_local  11969   20677
numa_hit                240854  239988
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              240851  239983
numa_other              3       5
numa_pages_migrated     1190    1016
numa_pte_updates        18106   27916

perf stats 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                     Before          After
cs                        61,053,158      60,899,307
migrations                551,586         544,668
faults                    244,174         270,834
cache-misses              74,326,766,973  74,543,455,635
sched:sched_move_numa     344             735
sched:sched_stick_numa    24              25
sched:sched_swap_numa     140             174
migrate:mm_migrate_pages  568             816

vmstat 8th warehouse Single JVM 4 Socket - 4  Node Power7 - PowerVM
Event                   Before  After
numa_hint_faults        6461    11059
numa_hint_faults_local  2283    4733
numa_hit                35661   41384
numa_huge_pte_updates   0       0
numa_interleave         0       0
numa_local              35661   41383
numa_other              0       1
numa_pages_migrated     568     815
numa_pte_updates        6518    11323
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NRik van Riel <riel@surriel.com>
Acked-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Jirka Hladky <jhladky@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1537552141-27815-2-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Fix kernel-doc warning for missing 'flags' parameter description:

../kernel/sched/fair.c:3371: warning: Function parameter or member 'flags' not described in 'attach_entity_load_avg'
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: ea14b57e ("sched/cpufreq: Provide migration hint")
Link: http://lkml.kernel.org/r/cdda0d42-880d-4229-a9f7-5899c977a063@infradead.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

It can happen that load_balance() finds a busiest group and then a
busiest rq but the calculated imbalance is in fact 0.

In such situation, detach_tasks() returns immediately and lets the
flag LBF_ALL_PINNED set. The busiest CPU is then wrongly assumed to
have pinned tasks and removed from the load balance mask. then, we
redo a load balance without the busiest CPU. This creates wrong load
balance situation and generates wrong task migration.

If the calculated imbalance is 0, it's useless to try to find a
busiest rq as no task will be migrated and we can return immediately.

This situation can happen with heterogeneous system or smp system when
RT tasks are decreasing the capacity of some CPUs.
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: jhugo@codeaurora.org
Link: http://lkml.kernel.org/r/1536306664-29827-1-git-send-email-vincent.guittot@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Since commit:

  523e979d ("sched/core: Use PELT for scale_rt_capacity()")

scale_rt_capacity() returns the remaining capacity and not a scale factor
to apply on cpu_capacity_orig. arch_scale_cpu() is directly called by
scale_rt_capacity() so we must take the sched_domain argument.
Reported-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 523e979d ("sched/core: Use PELT for scale_rt_capacity()")
Link: http://lkml.kernel.org/r/20180904093626.GA23936@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

When a task which previously ran on a given CPU is remotely queued to
wake up on that same CPU, there is a period where the task's state is
TASK_WAKING and its vruntime is not normalized. This is not accounted
for in vruntime_normalized() which will cause an error in the task's
vruntime if it is switched from the fair class during this time.

For example if it is boosted to RT priority via rt_mutex_setprio(),
rq->min_vruntime will not be subtracted from the task's vruntime but
it will be added again when the task returns to the fair class. The
task's vruntime will have been erroneously doubled and the effective
priority of the task will be reduced.

Note this will also lead to inflation of all vruntimes since the doubled
vruntime value will become the rq's min_vruntime when other tasks leave
the rq. This leads to repeated doubling of the vruntime and priority
penalty.

Fix this by recognizing a WAKING task's vruntime as normalized only if
sched_remote_wakeup is true. This indicates a migration, in which case
the vruntime would have been normalized in migrate_task_rq_fair().

Based on a similar patch from John Dias <joaodias@google.com>.
Suggested-by: NPeter Zijlstra <peterz@infradead.org>
Tested-by: NDietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: NSteve Muckle <smuckle@google.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Redpath <Chris.Redpath@arm.com>
Cc: John Dias <joaodias@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Miguel de Dios <migueldedios@google.com>
Cc: Morten Rasmussen <Morten.Rasmussen@arm.com>
Cc: Patrick Bellasi <Patrick.Bellasi@arm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Quentin Perret <quentin.perret@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Todd Kjos <tkjos@google.com>
Cc: kernel-team@android.com
Fixes: b5179ac7 ("sched/fair: Prepare to fix fairness problems on migration")
Link: http://lkml.kernel.org/r/20180831224217.169476-1-smuckle@google.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

update_blocked_averages() is called to periodiccally decay the stalled load
of idle CPUs and to sync all loads before running load balance.

When cfs rq is idle, it trigs a load balance during pick_next_task_fair()
in order to potentially pull tasks and to use this newly idle CPU. This
load balance happens whereas prev task from another class has not been put
and its utilization updated yet. This may lead to wrongly account running
time as idle time for RT or DL classes.

Test that no RT or DL task is running when updating their utilization in
update_blocked_averages().

We still update RT and DL utilization instead of simply skipping them to
make sure that all metrics are synced when used during load balance.
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 371bf427 ("sched/rt: Add rt_rq utilization tracking")
Fixes: 3727e0e1 ("sched/dl: Add dl_rq utilization tracking")
Link: http://lkml.kernel.org/r/1535728975-22799-1-git-send-email-vincent.guittot@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

numa_migrate_preferred() is called periodically or when task preferred
node changes. Preferred node evaluations happen once per scan sequence.

If the scan completion happens just after the periodic NUMA migration,
then we try to migrate to the preferred node and the preferred node might
change, needing another node migration.

Avoid this by checking for scan sequence completion only when checking
for periodic migration.

Running SPECjbb2005 on a 4 node machine and comparing bops/JVM
JVMS  LAST_PATCH  WITH_PATCH  %CHANGE
16    25862.6     26158.1     1.14258
1     74357       72725       -2.19482

Running SPECjbb2005 on a 16 node machine and comparing bops/JVM
JVMS  LAST_PATCH  WITH_PATCH  %CHANGE
8     117019      113992      -2.58
1     179095      174947      -2.31

(numbers from v1 based on v4.17-rc5)
Testcase       Time:         Min         Max         Avg      StdDev
numa01.sh      Real:      449.46      770.77      615.22      101.70
numa01.sh       Sys:      132.72      208.17      170.46       24.96
numa01.sh      User:    39185.26    60290.89    50066.76     6807.84
numa02.sh      Real:       60.85       61.79       61.28        0.37
numa02.sh       Sys:       15.34       24.71       21.08        3.61
numa02.sh      User:     5204.41     5249.85     5231.21       17.60
numa03.sh      Real:      785.50      916.97      840.77       44.98
numa03.sh       Sys:      108.08      133.60      119.43        8.82
numa03.sh      User:    61422.86    70919.75    64720.87     3310.61
numa04.sh      Real:      429.57      587.37      480.80       57.40
numa04.sh       Sys:      240.61      321.97      290.84       33.58
numa04.sh      User:    34597.65    40498.99    37079.48     2060.72
numa05.sh      Real:      392.09      431.25      414.65       13.82
numa05.sh       Sys:      229.41      372.48      297.54       53.14
numa05.sh      User:    33390.86    34697.49    34222.43      556.42

Testcase       Time:         Min         Max         Avg      StdDev 	%Change
numa01.sh      Real:      424.63      566.18      498.12       59.26 	 23.50%
numa01.sh       Sys:      160.19      256.53      208.98       37.02 	 -18.4%
numa01.sh      User:    37320.00    46225.58    42001.57     3482.45 	 19.20%
numa02.sh      Real:       60.17       62.47       60.91        0.85 	 0.607%
numa02.sh       Sys:       15.30       22.82       17.04        2.90 	 23.70%
numa02.sh      User:     5202.13     5255.51     5219.08       20.14 	 0.232%
numa03.sh      Real:      823.91      844.89      833.86        8.46 	 0.828%
numa03.sh       Sys:      130.69      148.29      140.47        6.21 	 -14.9%
numa03.sh      User:    62519.15    64262.20    63613.38      620.05 	 1.740%
numa04.sh      Real:      515.30      603.74      548.56       30.93 	 -12.3%
numa04.sh       Sys:      459.73      525.48      489.18       21.63 	 -40.5%
numa04.sh      User:    40561.96    44919.18    42047.87     1526.85 	 -11.8%
numa05.sh      Real:      396.58      454.37      421.13       19.71 	 -1.53%
numa05.sh       Sys:      208.72      422.02      348.90       73.60 	 -14.7%
numa05.sh      User:    33124.08    36109.35    34846.47     1089.74 	 -1.79%
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1529514181-9842-20-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

On NUMA_BACKPLANE and NUMA_GLUELESS_MESH systems, tasks/memory should be
consolidated to the closest group of nodes. In such a case, relying on
group_fault metric may not always help to consolidate. There can always
be a case where a node closer to the preferred node may have lesser
faults than a node further away from the preferred node. In such a case,
moving to node with more faults might avoid numa consolidation.

Using group_weight would help to consolidate task/memory around the
preferred_node.

While here, to be on the conservative side, don't override migrate thread
degrades locality logic for CPU_NEWLY_IDLE load balancing.

Note: Similar problems exist with should_numa_migrate_memory and will be
dealt separately.

Running SPECjbb2005 on a 4 node machine and comparing bops/JVM
JVMS  LAST_PATCH  WITH_PATCH  %CHANGE
16    25645.4     25960       1.22
1     72142       73550       1.95

Running SPECjbb2005 on a 16 node machine and comparing bops/JVM
JVMS  LAST_PATCH  WITH_PATCH  %CHANGE
8     110199      120071      8.958
1     176303      176249      -0.03

(numbers from v1 based on v4.17-rc5)
Testcase       Time:         Min         Max         Avg      StdDev
numa01.sh      Real:      490.04      774.86      596.26       96.46
numa01.sh       Sys:      151.52      242.88      184.82       31.71
numa01.sh      User:    41418.41    60844.59    48776.09     6564.27
numa02.sh      Real:       60.14       62.94       60.98        1.00
numa02.sh       Sys:       16.11       30.77       21.20        5.28
numa02.sh      User:     5184.33     5311.09     5228.50       44.24
numa03.sh      Real:      790.95      856.35      826.41       24.11
numa03.sh       Sys:      114.93      118.85      117.05        1.63
numa03.sh      User:    60990.99    64959.28    63470.43     1415.44
numa04.sh      Real:      434.37      597.92      504.87       59.70
numa04.sh       Sys:      237.63      397.40      289.74       55.98
numa04.sh      User:    34854.87    41121.83    38572.52     2615.84
numa05.sh      Real:      386.77      448.90      417.22       22.79
numa05.sh       Sys:      149.23      379.95      303.04       79.55
numa05.sh      User:    32951.76    35959.58    34562.18     1034.05

Testcase       Time:         Min         Max         Avg      StdDev 	 %Change
numa01.sh      Real:      493.19      672.88      597.51       59.38 	 -0.20%
numa01.sh       Sys:      150.09      245.48      207.76       34.26 	 -11.0%
numa01.sh      User:    41928.51    53779.17    48747.06     3901.39 	 0.059%
numa02.sh      Real:       60.63       62.87       61.22        0.83 	 -0.39%
numa02.sh       Sys:       16.64       27.97       20.25        4.06 	 4.691%
numa02.sh      User:     5222.92     5309.60     5254.03       29.98 	 -0.48%
numa03.sh      Real:      821.52      902.15      863.60       32.41 	 -4.30%
numa03.sh       Sys:      112.04      130.66      118.35        7.08 	 -1.09%
numa03.sh      User:    62245.16    69165.14    66443.04     2450.32 	 -4.47%
numa04.sh      Real:      414.53      519.57      476.25       37.00 	 6.009%
numa04.sh       Sys:      181.84      335.67      280.41       54.07 	 3.327%
numa04.sh      User:    33924.50    39115.39    37343.78     1934.26 	 3.290%
numa05.sh      Real:      408.30      441.45      417.90       12.05 	 -0.16%
numa05.sh       Sys:      233.41      381.60      295.58       57.37 	 2.523%
numa05.sh      User:    33301.31    35972.50    34335.19      938.94 	 0.661%
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1529514181-9842-16-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

The metrics for updating scan periods are local or task specific.
Currently this update happens under the numa_group lock, which seems
unnecessary. Hence move this update outside the lock.

Running SPECjbb2005 on a 4 node machine and comparing bops/JVM
JVMS  LAST_PATCH  WITH_PATCH  %CHANGE
16    25355.9     25645.4     1.141
1     72812       72142       -0.92
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NRik van Riel <riel@surriel.com>
Acked-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1529514181-9842-15-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

task_numa_find_cpu() helps to find the CPU to swap/move the task to.
It's guarded by numa_has_capacity(). However node not having capacity
shouldn't deter a task swapping if it helps NUMA placement.

Further load_too_imbalanced(), which evaluates possibilities of move/swap,
provides similar checks as numa_has_capacity.

Hence remove numa_has_capacity() to enhance possibilities of task
swapping even if load is imbalanced.

Running SPECjbb2005 on a 4 node machine and comparing bops/JVM
JVMS  LAST_PATCH  WITH_PATCH  %CHANGE
16    25657.9     25804.1     0.569
1     74435       73413       -1.37
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NRik van Riel <riel@surriel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1529514181-9842-13-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>