We watch for tasks that sleep extended periods and don't allow one single
prolonged sleep period from elevating priority to maximum bonus to prevent cpu
bound tasks from getting high priority with single long sleeps.  There is a
bug in the current code that also penalises tasks that already have high
priority.  Correct that bug.
Signed-off-by: NCon Kolivas <kernel@kolivas.org>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Alterations to the pipe code in the kernel made it possible for relative
starvation to occur with tasks that slept waiting on a pipe getting unfair
priority bonuses even if they were otherwise fully cpu bound so the
TASK_NONINTERACTIVE flag was introduced which prevented any change to
sleep_avg while sleeping waiting on a pipe.  This change also leads to the
converse though, preventing any priority boost from occurring in truly
interactive tasks that wait on pipes.

Convert the TASK_NONINTERACTIVE flag to set sleep_type to SLEEP_NONINTERACTIVE
which will allow a linear bonus to priority based on sleep time thus allowing
interactive tasks to get high priority if they sleep enough.
Signed-off-by: NCon Kolivas <kernel@kolivas.org>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The activated flag in task_struct is used to track different sleep types and
its usage is somewhat obfuscated.  Convert the variable to an enum with more
descriptive names without altering the function.
Signed-off-by: NCon Kolivas <kernel@kolivas.org>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Currently, count_active_tasks() calls both nr_running() &
nr_interruptible().  Each of these functions does a "for_each_cpu" & reads
values from the runqueue of each cpu.  Although this is not a lot of
instructions, each runqueue may be located on different node.  Depending on
the architecture, a unique TLB entry may be required to access each
runqueue.

Since there may be more runqueues than cpu TLB entries, a scan of all
runqueues can trash the TLB.  Each memory reference incurs a TLB miss &
refill.

In addition, the runqueue cacheline that contains nr_running &
nr_uninterruptible may be evicted from the cache between the two passes.
This causes unnecessary cache misses.

Combining nr_running() & nr_interruptible() into a single function
substantially reduces the TLB & cache misses on large systems.  This should
have no measureable effect on smaller systems.

On a 128p IA64 system running a memory stress workload, the new function
reduced the overhead of calc_load() from 605 usec/call to 324 usec/call.
Signed-off-by: NJack Steiner <steiner@sgi.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

replaces for_each_cpu with for_each_possible_cpu().
Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Current sched groups power calculation for allnodes_domains is wrong.  We
should really be using cumulative power of the physical packages in that
group (similar to the calculation in node_domains)
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a new sched domain for representing multi-core with shared caches
between cores.  Consider a dual package system, each package containing two
cores and with last level cache shared between cores with in a package.  If
there are two runnable processes, with this appended patch those two
processes will be scheduled on different packages.

On such systems, with this patch we have observed 8% perf improvement with
specJBB(2 warehouse) benchmark and 35% improvement with CFP2000 rate(with 2
users).

This new domain will come into play only on multi-core systems with shared
caches.  On other systems, this sched domain will be removed by domain
degeneration code.  This new domain can be also used for implementing power
savings policy (see OLS 2005 CMP kernel scheduler paper for more details..
I will post another patch for power savings policy soon)

Most of the arch/* file changes are for cpu_coregroup_map() implementation.
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

small schedule() microoptimization.
Signed-off-by: NAndreas Mohr <andi@lisas.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Is a truncation error in kernel/sched.c triggered when the nice value is
negative.  The affected code is used in the TASK_INTERACTIVE macro.

The code is:
#define SCALE(v1,v1_max,v2_max) \
	(v1) * (v2_max) / (v1_max)

which is used in this way:
SCALE(TASK_NICE(p), 40, MAX_BONUS)

Comments in the code says:
  * This part scales the interactivity limit depending on niceness.
  *
  * We scale it linearly, offset by the INTERACTIVE_DELTA delta.
  * Here are a few examples of different nice levels:
  *
  *  TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
  *  TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
  *  TASK_INTERACTIVE(  0): [1,1,1,1,0,0,0,0,0,0,0]
  *  TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
  *  TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
  *
  * (the X axis represents the possible -5 ... 0 ... +5 dynamic
  *  priority range a task can explore, a value of '1' means the
  *  task is rated interactive.)

However, the current code does not scale it linearly and the result differs
from the given examples.  If the mathematical function "floor" is used when
the nice value is negative instead of the truncation one gets when using
integer division, the result conforms to the documentation.

Output of TASK_INTERACTIVE when using the kernel code:
nice    dynamic priorities
-20     1     1     1     1     1     1     1     1     1     0     0
-19     1     1     1     1     1     1     1     1     0     0     0
-18     1     1     1     1     1     1     1     1     0     0     0
-17     1     1     1     1     1     1     1     1     0     0     0
-16     1     1     1     1     1     1     1     1     0     0     0
-15     1     1     1     1     1     1     1     0     0     0     0
-14     1     1     1     1     1     1     1     0     0     0     0
-13     1     1     1     1     1     1     1     0     0     0     0
-12     1     1     1     1     1     1     1     0     0     0     0
-11     1     1     1     1     1     1     0     0     0     0     0
-10     1     1     1     1     1     1     0     0     0     0     0
  -9     1     1     1     1     1     1     0     0     0     0     0
  -8     1     1     1     1     1     1     0     0     0     0     0
  -7     1     1     1     1     1     0     0     0     0     0     0
  -6     1     1     1     1     1     0     0     0     0     0     0
  -5     1     1     1     1     1     0     0     0     0     0     0
  -4     1     1     1     1     1     0     0     0     0     0     0
  -3     1     1     1     1     0     0     0     0     0     0     0
  -2     1     1     1     1     0     0     0     0     0     0     0
  -1     1     1     1     1     0     0     0     0     0     0     0
  0      1     1     1     1     0     0     0     0     0     0     0
  1      1     1     1     1     0     0     0     0     0     0     0
  2      1     1     1     1     0     0     0     0     0     0     0
  3      1     1     1     1     0     0     0     0     0     0     0
  4      1     1     1     0     0     0     0     0     0     0     0
  5      1     1     1     0     0     0     0     0     0     0     0
  6      1     1     1     0     0     0     0     0     0     0     0
  7      1     1     1     0     0     0     0     0     0     0     0
  8      1     1     0     0     0     0     0     0     0     0     0
  9      1     1     0     0     0     0     0     0     0     0     0
10      1     1     0     0     0     0     0     0     0     0     0
11      1     1     0     0     0     0     0     0     0     0     0
12      1     0     0     0     0     0     0     0     0     0     0
13      1     0     0     0     0     0     0     0     0     0     0
14      1     0     0     0     0     0     0     0     0     0     0
15      1     0     0     0     0     0     0     0     0     0     0
16      0     0     0     0     0     0     0     0     0     0     0
17      0     0     0     0     0     0     0     0     0     0     0
18      0     0     0     0     0     0     0     0     0     0     0
19      0     0     0     0     0     0     0     0     0     0     0

Output of TASK_INTERACTIVE when using "floor"
nice    dynamic priorities
-20     1     1     1     1     1     1     1     1     1     0     0
-19     1     1     1     1     1     1     1     1     1     0     0
-18     1     1     1     1     1     1     1     1     1     0     0
-17     1     1     1     1     1     1     1     1     1     0     0
-16     1     1     1     1     1     1     1     1     0     0     0
-15     1     1     1     1     1     1     1     1     0     0     0
-14     1     1     1     1     1     1     1     1     0     0     0
-13     1     1     1     1     1     1     1     1     0     0     0
-12     1     1     1     1     1     1     1     0     0     0     0
-11     1     1     1     1     1     1     1     0     0     0     0
-10     1     1     1     1     1     1     1     0     0     0     0
  -9     1     1     1     1     1     1     1     0     0     0     0
  -8     1     1     1     1     1     1     0     0     0     0     0
  -7     1     1     1     1     1     1     0     0     0     0     0
  -6     1     1     1     1     1     1     0     0     0     0     0
  -5     1     1     1     1     1     1     0     0     0     0     0
  -4     1     1     1     1     1     0     0     0     0     0     0
  -3     1     1     1     1     1     0     0     0     0     0     0
  -2     1     1     1     1     1     0     0     0     0     0     0
  -1     1     1     1     1     1     0     0     0     0     0     0
   0     1     1     1     1     0     0     0     0     0     0     0
   1     1     1     1     1     0     0     0     0     0     0     0
   2     1     1     1     1     0     0     0     0     0     0     0
   3     1     1     1     1     0     0     0     0     0     0     0
   4     1     1     1     0     0     0     0     0     0     0     0
   5     1     1     1     0     0     0     0     0     0     0     0
   6     1     1     1     0     0     0     0     0     0     0     0
   7     1     1     1     0     0     0     0     0     0     0     0
   8     1     1     0     0     0     0     0     0     0     0     0
   9     1     1     0     0     0     0     0     0     0     0     0
  10     1     1     0     0     0     0     0     0     0     0     0
  11     1     1     0     0     0     0     0     0     0     0     0
  12     1     0     0     0     0     0     0     0     0     0     0
  13     1     0     0     0     0     0     0     0     0     0     0
  14     1     0     0     0     0     0     0     0     0     0     0
  15     1     0     0     0     0     0     0     0     0     0     0
  16     0     0     0     0     0     0     0     0     0     0     0
  17     0     0     0     0     0     0     0     0     0     0     0
  18     0     0     0     0     0     0     0     0     0     0     0
  19     0     0     0     0     0     0     0     0     0     0     0
Signed-off-by: NMartin Andersson <martin.andersson@control.lth.se>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Con Kolivas <kernel@kolivas.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

When kretprobe probes the schedule() function, if the probed process exits
then schedule() will never return, so some kretprobe instances will never
be recycled.

In this patch the parent process will recycle retprobe instances of the
probed function and there will be no memory leak of kretprobe instances.
Signed-off-by: Nbibo mao <bibo.mao@intel.com>
Cc: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Consolidate all kernel bug printouts to begin with the "BUG: " string.
Makes it easier to find them in large bootup logs.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

We have noticed lockups during boot when stress testing kexec on ppc64.
Two cpus would deadlock in scheduler code trying to grab already taken
spinlocks.

The double_rq_lock code uses the address of the runqueue to order the
taking of multiple locks.  This address is a per cpu variable:

	if (rq1 < rq2) {
		spin_lock(&rq1->lock);
		spin_lock(&rq2->lock);
	} else {
		spin_lock(&rq2->lock);
		spin_lock(&rq1->lock);
	}

On the other hand, the code in wake_sleeping_dependent uses the cpu id
order to grab locks:

	for_each_cpu_mask(i, sibling_map)
		spin_lock(&cpu_rq(i)->lock);

This means we rely on the address of per cpu data increasing as cpu ids
increase.  While this will be true for the generic percpu implementation it
may not be true for arch specific implementations.

One way to solve this is to always take runqueues in cpu id order. To do
this we add a cpu variable to the runqueue and check it in the
double runqueue locking functions.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Remove the sleep_avg multiplier.  This multiplier was necessary back when
we had 10 seconds of dynamic range in sleep_avg, but now that we only have
one second, it causes that one second to be compressed down to 100ms in
some cases.  This is particularly noticeable when compiling a kernel in a
slow NFS mount, and I believe it to be a very likely candidate for other
recently reported network related interactivity problems.

In testing, I can detect no negative impact of this removal.
Signed-off-by: NMike Galbraith <efault@gmx.de>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The patch '[PATCH] RCU signal handling' [1] added an export for
__put_task_struct_cb, a put_task_struct helper newly introduced in that
patch.  But the put_task_struct couldn't be used modular previously as
__put_task_struct wasn't exported.  There are not callers of it in modular
code, and it shouldn't be exported because we don't want drivers to hold
references to task_structs.

This patch removes the export and folds __put_task_struct into
__put_task_struct_cb as there's no other caller.

[1] http://www2.kernel.org/git/gitweb.cgi?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e56d090310d7625ecb43a1eeebd479f04affb48bSigned-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NPaul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Idle threads should have a sane ->timestamp value, to avoid init kernel
thread(s) from inheriting it and causing miscalculations in
try_to_wake_up().

Reported-by: Mike Galbraith <efault@gmx.de>.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Just to be safe, we should not trigger a conditional reschedule during
the early boot sequence.  We've historically done some questionable
early on, and the safety warnings in __might_sleep() are generally
turned off during that period, so there might be problems lurking.

This affects CONFIG_PREEMPT_VOLUNTARY, which takes over might_sleep() to
cause a voluntary conditional reschedule.
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Heiko Carstens <heiko.carstens@de.ibm.com> wrote:

  The boot sequence on s390 sometimes takes ages and we spend a very long
  time (up to one or two minutes) in calibrate_migration_costs.  The time
  spent there differs from boot to boot.  Also the calculated costs differ
  a lot.  I've seen differences by up to a factor of 15 (yes, factor not
  percent).  Also I doubt that making these measurements make much sense on
  a completely virtualized architecture where you cannot tell how much cpu
  time you will get anyway.

So introduce the CONFIG_DEFAULT_MIGRATION_COST method for an architecture
to set the scheduler migration costs.  This turns off automatic detection
of migration costs.  Makes sense on virtual platforms, where migration
costs are hard to measure accurately.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Revert commit d7102e95:

    [PATCH] sched: filter affine wakeups

Apparently caused more than 10% performance regression for aim7 benchmark.
The setup in use is 16-cpu HP rx8620, 64Gb of memory and 12 MSA1000s with 144
disks.  Each disk is 72Gb with a single ext3 filesystem (courtesy of HP, who
supplied benchmark results).

The problem is, for aim7, the wake-up pattern is random, but it still needs
load balancing action in the wake-up path to achieve best performance.  With
the above commit, lack of load balancing hurts that workload.

However, for workloads like database transaction processing, the requirement
is exactly opposite.  In the wake up path, best performance is achieved with
absolutely zero load balancing.  We simply wake up the process on the CPU that
it was previously run.  Worst performance is obtained when we do load
balancing at wake up.

There isn't an easy way to auto detect the workload characteristics.  Ingo's
earlier patch that detects idle CPU and decide whether to load balance or not
doesn't perform with aim7 either since all CPUs are busy (it causes even
bigger perf.  regression).

Revert commit d7102e95, which causes more
than 10% performance regression with aim7.
Signed-off-by: NKen Chen <kenneth.w.chen@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I don't think the code is quite ready, which is why I asked for Peter's
additions to also be merged before I acked it (although it turned out that
it still isn't quite ready with his additions either).

Basically I have had similar observations to Suresh in that it does not
play nicely with the rest of the balancing infrastructure (and raised
similar concerns in my review).

The samples (group of 4) I got for "maximum recorded imbalance" on a 2x2
SMP+HT Xeon are as follows:

            | Following boot | hackbench 20        | hackbench 40
 -----------+----------------+---------------------+---------------------
 2.6.16-rc2 | 30,37,100,112  | 5600,5530,6020,6090 | 6390,7090,8760,8470
 +nosmpnice |  3, 2,  4,  2  |   28, 150, 294, 132 |  348, 348, 294, 347

Hackbench raw performance is down around 15% with smpnice (but that in
itself isn't a huge deal because it is just a benchmark).  However, the
samples show that the imbalance passed into move_tasks is increased by
about a factor of 10-30.  I think this would also go some way to explaining
latency blips turning up in the balancing code (though I haven't actually
measured that).

We'll probably have to revert this in the SUSE kernel.

Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: "Martin J. Bligh" <mbligh@aracnet.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

migration_cost prints after every CPU hotplug event.  Make it print only
once at boot.
Signed-off-by: NChuck Ebbert <76306.1226@compuserve.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

percpu_data blindly allocates bootmem memory to store NR_CPUS instances of
cpudata, instead of allocating memory only for possible cpus.

As a preparation for changing that, we need to convert various 0 -> NR_CPUS
loops to use for_each_cpu().

(The above only applies to users of asm-generic/percpu.h.  powerpc has gone it
alone and is presently only allocating memory for present CPUs, so it's
currently corrupting memory).
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Jens Axboe <axboe@suse.de>
Cc: Anton Blanchard <anton@samba.org>
Acked-by: NWilliam Irwin <wli@holomorphy.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Change sched_getaffinity() so that it returns a bitmap that indicates the
legally schedulable cpus that a task is allowed to run on.

Without this patch, if CONFIG_HOTPLUG_CPU is enabled, sched_getaffinity()
unconditionally returns (at least on IA64) a mask with NR_CPUS bits set.
This conveys no useful infornmation except for a kernel compile option.

This fixes a breakage we obseved running recent kernels. We have MPI jobs
that use sched_getaffinity() to determine where to place their threads.
Placing them on non-existant cpus is problematic :-)
Signed-off-by: NJack Steiner <steiner@sgi.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Nathan Lynch <ntl@pobox.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This reduces the amount of time the migration cost calculations cost
during bootup. Based on numbers by Tony Luck <tony.luck@intel.com>.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Currently, a negative policy argument passed into the
'sys_sched_setscheduler()' system call, will return with success.  However,
the manpage for 'sys_sched_setscheduler' says:

EINVAL The scheduling policy is not one of the recognized policies, or the
              parameter p does not make sense for the policy.
Signed-off-by: NJason Baron <jbaron@redhat.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Remove the "inline" keyword from a bunch of big functions in the kernel with
the goal of shrinking it by 30kb to 40kb
Signed-off-by: NArjan van de Ven <arjan@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NJeff Garzik <jgarzik@pobox.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a new SCHED_BATCH (3) scheduling policy: such tasks are presumed
CPU-intensive, and will acquire a constant +5 priority level penalty.  Such
policy is nice for workloads that are non-interactive, but which do not
want to give up their nice levels.  The policy is also useful for workloads
that want a deterministic scheduling policy without interactivity causing
extra preemptions (between that workload's tasks).
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

)

From: Nick Piggin <nickpiggin@yahoo.com.au>

Track the last waker CPU, and only consider wakeup-balancing if there's a
match between current waker CPU and the previous waker CPU.  This ensures
that there is some correlation between two subsequent wakeup events before
we move the task.  Should help random-wakeup workloads on large SMP
systems, by reducing the migration attempts by a factor of nr_cpus.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

)

From: Ingo Molnar <mingo@elte.hu>

This is the latest version of the scheduler cache-hot-auto-tune patch.

The first problem was that detection time scaled with O(N^2), which is
unacceptable on larger SMP and NUMA systems. To solve this:

- I've added a 'domain distance' function, which is used to cache
  measurement results. Each distance is only measured once. This means
  that e.g. on NUMA distances of 0, 1 and 2 might be measured, on HT
  distances 0 and 1, and on SMP distance 0 is measured. The code walks
  the domain tree to determine the distance, so it automatically follows
  whatever hierarchy an architecture sets up. This cuts down on the boot
  time significantly and removes the O(N^2) limit. The only assumption
  is that migration costs can be expressed as a function of domain
  distance - this covers the overwhelming majority of existing systems,
  and is a good guess even for more assymetric systems.

  [ People hacking systems that have assymetries that break this
    assumption (e.g. different CPU speeds) should experiment a bit with
    the cpu_distance() function. Adding a ->migration_distance factor to
    the domain structure would be one possible solution - but lets first
    see the problem systems, if they exist at all. Lets not overdesign. ]

Another problem was that only a single cache-size was used for measuring
the cost of migration, and most architectures didnt set that variable
up. Furthermore, a single cache-size does not fit NUMA hierarchies with
L3 caches and does not fit HT setups, where different CPUs will often
have different 'effective cache sizes'. To solve this problem:

- Instead of relying on a single cache-size provided by the platform and
  sticking to it, the code now auto-detects the 'effective migration
  cost' between two measured CPUs, via iterating through a wide range of
  cachesizes. The code searches for the maximum migration cost, which
  occurs when the working set of the test-workload falls just below the
  'effective cache size'. I.e. real-life optimized search is done for
  the maximum migration cost, between two real CPUs.

  This, amongst other things, has the positive effect hat if e.g. two
  CPUs share a L2/L3 cache, a different (and accurate) migration cost
  will be found than between two CPUs on the same system that dont share
  any caches.

(The reliable measurement of migration costs is tricky - see the source
for details.)

Furthermore i've added various boot-time options to override/tune
migration behavior.

Firstly, there's a blanket override for autodetection:

	migration_cost=1000,2000,3000

will override the depth 0/1/2 values with 1msec/2msec/3msec values.

Secondly, there's a global factor that can be used to increase (or
decrease) the autodetected values:

	migration_factor=120

will increase the autodetected values by 20%. This option is useful to
tune things in a workload-dependent way - e.g. if a workload is
cache-insensitive then CPU utilization can be maximized by specifying
migration_factor=0.

I've tested the autodetection code quite extensively on x86, on 3
P3/Xeon/2MB, and the autodetected values look pretty good:

Dual Celeron (128K L2 cache):

 ---------------------
 migration cost matrix (max_cache_size: 131072, cpu: 467 MHz):
 ---------------------
           [00]    [01]
 [00]:     -     1.7(1)
 [01]:   1.7(1)    -
 ---------------------
 cacheflush times [2]: 0.0 (0) 1.7 (1784008)
 ---------------------

Here the slow memory subsystem dominates system performance, and even
though caches are small, the migration cost is 1.7 msecs.

Dual HT P4 (512K L2 cache):

 ---------------------
 migration cost matrix (max_cache_size: 524288, cpu: 2379 MHz):
 ---------------------
           [00]    [01]    [02]    [03]
 [00]:     -     0.4(1)  0.0(0)  0.4(1)
 [01]:   0.4(1)    -     0.4(1)  0.0(0)
 [02]:   0.0(0)  0.4(1)    -     0.4(1)
 [03]:   0.4(1)  0.0(0)  0.4(1)    -
 ---------------------
 cacheflush times [2]: 0.0 (33900) 0.4 (448514)
 ---------------------

Here it can be seen that there is no migration cost between two HT
siblings (CPU#0/2 and CPU#1/3 are separate physical CPUs). A fast memory
system makes inter-physical-CPU migration pretty cheap: 0.4 msecs.

8-way P3/Xeon [2MB L2 cache]:

 ---------------------
 migration cost matrix (max_cache_size: 2097152, cpu: 700 MHz):
 ---------------------
           [00]    [01]    [02]    [03]    [04]    [05]    [06]    [07]
 [00]:     -    19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
 [01]:  19.2(1)    -    19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
 [02]:  19.2(1) 19.2(1)    -    19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
 [03]:  19.2(1) 19.2(1) 19.2(1)    -    19.2(1) 19.2(1) 19.2(1) 19.2(1)
 [04]:  19.2(1) 19.2(1) 19.2(1) 19.2(1)    -    19.2(1) 19.2(1) 19.2(1)
 [05]:  19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)    -    19.2(1) 19.2(1)
 [06]:  19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)    -    19.2(1)
 [07]:  19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)    -
 ---------------------
 cacheflush times [2]: 0.0 (0) 19.2 (19281756)
 ---------------------

This one has huge caches and a relatively slow memory subsystem - so the
migration cost is 19 msecs.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAshok Raj <ashok.raj@intel.com>
Signed-off-by: NKen Chen <kenneth.w.chen@intel.com>
Cc: <wilder@us.ibm.com>
Signed-off-by: NJohn Hawkes <hawkes@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

They are referred to often so avoid potential false sharing for them.
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

- Move capable() from sched.h to capability.h;

- Use <linux/capability.h> where capable() is used
	(in include/, block/, ipc/, kernel/, a few drivers/,
	mm/, security/, & sound/;
	many more drivers/ to go)
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

more mutex debugging: check for held locks during memory freeing,
task exit, enable sysrq printouts, etc.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NArjan van de Ven <arjan@infradead.org>

RCU tasklist_lock and RCU signal handling: send signals RCU-read-locked
instead of tasklist_lock read-locked.  This is a scalability improvement on
SMP and a preemption-latency improvement under PREEMPT_RCU.
Signed-off-by: NPaul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NWilliam Irwin <wli@holomorphy.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

encapsulates the rest of arch-dependent operations with thread_info access.
Two new helpers - setup_thread_stack() and end_of_stack().  For normal case
the former consists of copying thread_info of parent to new thread_info and
the latter returns pointer immediately past the end of thread_info.
Signed-off-by: NAl Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: NRoman Zippel <zippel@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

new helper - task_thread_info(task).  On platforms that have thread_info
allocated separately (i.e.  in default case) it simply returns
task->thread_info.  m68k wants (and for good reasons) to embed its thread_info
into task_struct.  So it will (in later patch) have task_thread_info() of its
own.  For now we just add a macro for generic case and convert existing
instances of its body in core kernel to uses of new macro.  Obviously safe -
all normal architectures get the same preprocessor output they used to get.
Signed-off-by: NAl Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: NRoman Zippel <zippel@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

recalc_task_prio() is called from activate_task() to calculate dynamic
priority and interactive credit for the activating task.  For real-time
scheduling process, all that dynamic calculation is thrown away at the end
because rt priority is fixed.  Patch to optimize recalc_task_prio() away
for rt processes.
Signed-off-by: NKen Chen <kenneth.w.chen@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Nick Piggin <piggin@cyberone.com.au>
Cc: Con Kolivas <kernel@kolivas.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Make some changes to the NEED_RESCHED and POLLING_NRFLAG to reduce
confusion, and make their semantics rigid.  Improves efficiency of
resched_task and some cpu_idle routines.

* In resched_task:
- TIF_NEED_RESCHED is only cleared with the task's runqueue lock held,
  and as we hold it during resched_task, then there is no need for an
  atomic test and set there. The only other time this should be set is
  when the task's quantum expires, in the timer interrupt - this is
  protected against because the rq lock is irq-safe.

- If TIF_NEED_RESCHED is set, then we don't need to do anything. It
  won't get unset until the task get's schedule()d off.

- If we are running on the same CPU as the task we resched, then set
  TIF_NEED_RESCHED and no further action is required.

- If we are running on another CPU, and TIF_POLLING_NRFLAG is *not* set
  after TIF_NEED_RESCHED has been set, then we need to send an IPI.

Using these rules, we are able to remove the test and set operation in
resched_task, and make clear the previously vague semantics of
POLLING_NRFLAG.

* In idle routines:
- Enter cpu_idle with preempt disabled. When the need_resched() condition
  becomes true, explicitly call schedule(). This makes things a bit clearer
  (IMO), but haven't updated all architectures yet.

- Many do a test and clear of TIF_NEED_RESCHED for some reason. According
  to the resched_task rules, this isn't needed (and actually breaks the
  assumption that TIF_NEED_RESCHED is only cleared with the runqueue lock
  held). So remove that. Generally one less locked memory op when switching
  to the idle thread.

- Many idle routines clear TIF_POLLING_NRFLAG, and only set it in the inner
  most polling idle loops. The above resched_task semantics allow it to be
  set until before the last time need_resched() is checked before going into
  a halt requiring interrupt wakeup.

  Many idle routines simply never enter such a halt, and so POLLING_NRFLAG
  can be always left set, completely eliminating resched IPIs when rescheduling
  the idle task.

  POLLING_NRFLAG width can be increased, to reduce the chance of resched IPIs.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Con Kolivas <kernel@kolivas.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The intermittent scheduling of the migration thread at ultra high priority
makes the smp nice handling see that runqueue as being heavily loaded.  The
migration thread itself actually handles the balancing so its influence on
priority balancing should be ignored.
Signed-off-by: NCon Kolivas <kernel@kolivas.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The priority biasing was off by mutliplying the total load by the total
priority bias and this ruins the ratio of loads between runqueues. This
patch should correct the ratios of loads between runqueues to be proportional
to overall load. -2nd attempt.

From: Dave Kleikamp <shaggy@austin.ibm.com>

  This patch fixes a divide-by-zero error that I hit on a two-way i386
  machine.  rq->nr_running is tested to be non-zero, but may change by the
  time it is used in the division.  Saving the value to a local variable
  ensures that the same value that is checked is used in the division.
Signed-off-by: NCon Kolivas <kernel@kolivas.org>
Signed-off-by: NDave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

To intensify the 'nice' support across physical cpus on SMP we can bias the
loads on idle rebalancing. To prevent idle rebalance from trying to pull tasks
from queues that appear heavily loaded we only bias the load if there is more
than one task running.

Add some minor micro-optimisations and have only one return from __source_load
and __target_load functions.

Fix the fact that target_load was not biased by priority when type == 0.
Signed-off-by: NCon Kolivas <kernel@kolivas.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Real time tasks' effect on prio_bias should be based on their real time
priority level instead of their static_prio which is based on nice.
Signed-off-by: NCon Kolivas <kernel@kolivas.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>