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  1. 19 8月, 2009 12 次提交
  3. 18 7月, 2009 1 次提交
    • T
      sched: fix load average accounting vs. cpu hotplug · a468d389
      由 Thomas Gleixner 提交于 
      The new load average code clears rq->calc_load_active on
CPU_ONLINE. That's wrong as the new onlined CPU might have got a
scheduler tick already and accounted the delta to the stale value of
the time we offlined the CPU.

Clear the value when we cleanup the dead CPU instead. 

Also move the update of the calc_load_update time for the newly online
CPU to CPU_UP_PREPARE to avoid that the CPU plays catch up with the
stale update time value.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      a468d389
  5. 11 7月, 2009 1 次提交
  7. 10 7月, 2009 3 次提交
  9. 19 6月, 2009 2 次提交
    • P
      perf_counter: Simplify and fix task migration counting · e5289d4a
      由 Peter Zijlstra 提交于 
      The task migrations counter was causing rare and hard to decypher
memory corruptions under load. After a day of debugging and bisection
we found that the problem was introduced with:

  3f731ca6: perf_counter: Fix cpu migration counter

Turning them off fixes the crashes. Incidentally, the whole
perf_counter_task_migration() logic can be done simpler as well,
by injecting a proper sw-counter event.

This cleanup also fixed the crashes. The precise failure mode is
not completely clear yet, but we are clearly not unhappy about
having a fix ;-)
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e5289d4a
    • O
      kthreads: simplify migration_thread() exit path · 371cbb38
      由 Oleg Nesterov 提交于 
      Now that kthread_stop() can be used even if the task has already exited,
we can kill the "wait_to_die:" loop in migration_thread().  But we must
pin rq->migration_thread after creation.

Actually, I don't think CPU_UP_CANCELED or CPU_DEAD should wait for
->migration_thread exit.  Perhaps we can simplify this code a bit more.
migration_call() can set ->should_stop and forget about this thread.  But
we need a new helper in kthred.c for that.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Vitaliy Gusev <vgusev@openvz.org
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      371cbb38
  11. 17 6月, 2009 1 次提交
  13. 12 6月, 2009 4 次提交
  15. 02 6月, 2009 2 次提交
    • P
      perf_counter: Fix cpu migration counter · 3f731ca6
      由 Paul Mackerras 提交于 
      This fixes the cpu migration software counter to count
correctly even when contexts get swapped from one task to
another.  Previously the cpu migration counts reported by perf
stat were bogus, ranging from negative to several thousand for
a single "lat_ctx 2 8 32" run.  With this patch the cpu
migration count reported for "lat_ctx 2 8 32" is almost always
between 35 and 44.

This fixes the problem by adding a call into the perf_counter
code from set_task_cpu when tasks are migrated.  This enables
us to use the generic swcounter code (with some modifications)
for the cpu migration counter.

This modifies the swcounter code to allow a NULL regs pointer
to be passed in to perf_swcounter_ctx_event() etc.  The cpu
migration counter does this because there isn't necessarily a
pt_regs struct for the task available.  In this case, the
counter will not have interrupt capability - but the migration
counter didn't have interrupt capability before, so this is no
loss.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <18979.35006.819769.416327@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      3f731ca6
    • P
      perf_counter: Initialize per-cpu context earlier on cpu up · f38b0820
      由 Paul Mackerras 提交于 
      This arranges for perf_counter's notifier for cpu hotplug
operations to be called earlier than the migration notifier in
sched.c by increasing its priority to 20, compared to the 10
for the migration notifier.  The reason for doing this is that
a subsequent commit to convert the cpu migration counter to use
the generic swcounter infrastructure will add a call into the
perf_counter subsystem when tasks get migrated.  Therefore the
perf_counter subsystem needs a chance to initialize its per-cpu
data for the new cpu before it can get called from the
migration code.

This also adds a comment to the migration notifier noting that
its priority needs to be lower than that of the perf_counter
notifier.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <18981.1900.792795.836858@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      f38b0820
  17. 24 5月, 2009 1 次提交
    • P
      perf_counter: Fix dynamic irq_period logging · e220d2dc
      由 Peter Zijlstra 提交于 
      We call perf_adjust_freq() from perf_counter_task_tick() which
is is called under the rq->lock causing lock recursion.
However, it's no longer required to be called under the
rq->lock, so remove it from under it.

Also, fix up some related comments.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090523163012.476197912@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e220d2dc
  19. 22 5月, 2009 1 次提交
    • P
      perf_counter: Optimize context switch between identical inherited contexts · 564c2b21
      由 Paul Mackerras 提交于 
      When monitoring a process and its descendants with a set of inherited
counters, we can often get the situation in a context switch where
both the old (outgoing) and new (incoming) process have the same set
of counters, and their values are ultimately going to be added together.
In that situation it doesn't matter which set of counters are used to
count the activity for the new process, so there is really no need to
go through the process of reading the hardware counters and updating
the old task's counters and then setting up the PMU for the new task.

This optimizes the context switch in this situation.  Instead of
scheduling out the perf_counter_context for the old task and
scheduling in the new context, we simply transfer the old context
to the new task and keep using it without interruption.  The new
context gets transferred to the old task.  This means that both
tasks still have a valid perf_counter_context, so no special case
is introduced when the old task gets scheduled in again, either on
this CPU or another CPU.

The equivalence of contexts is detected by keeping a pointer in
each cloned context pointing to the context it was cloned from.
To cope with the situation where a context is changed by adding
or removing counters after it has been cloned, we also keep a
generation number on each context which is incremented every time
a context is changed.  When a context is cloned we take a copy
of the parent's generation number, and two cloned contexts are
equivalent only if they have the same parent and the same
generation number.  In order that the parent context pointer
remains valid (and is not reused), we increment the parent
context's reference count for each context cloned from it.

Since we don't have individual fds for the counters in a cloned
context, the only thing that can make two clones of a given parent
different after they have been cloned is enabling or disabling all
counters with prctl.  To account for this, we keep a count of the
number of enabled counters in each context.  Two contexts must have
the same number of enabled counters to be considered equivalent.

Here are some measurements of the context switch time as measured with
the lat_ctx benchmark from lmbench, comparing the times obtained with
and without this patch series:

		-----Unmodified-----		With this patch series
Counters:	none	2 HW	4H+4S	none	2 HW	4H+4S

2 processes:
Average		3.44	6.45	11.24	3.12	3.39	3.60
St dev		0.04	0.04	0.13	0.05	0.17	0.19

8 processes:
Average		6.45	8.79	14.00	5.57	6.23	7.57
St dev		1.27	1.04	0.88	1.42	1.46	1.42

32 processes:
Average		5.56	8.43	13.78	5.28	5.55	7.15
St dev		0.41	0.47	0.53	0.54	0.57	0.81

The numbers are the mean and standard deviation of 20 runs of
lat_ctx.  The "none" columns are lat_ctx run directly without any
counters.  The "2 HW" columns are with lat_ctx run under perfstat,
counting cycles and instructions.  The "4H+4S" columns are lat_ctx run
under perfstat with 4 hardware counters and 4 software counters
(cycles, instructions, cache references, cache misses, task
clock, context switch, cpu migrations, and page faults).

[ Impact: performance optimization of counter context-switches ]
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <18966.10666.517218.332164@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      564c2b21
  21. 19 5月, 2009 1 次提交
  23. 15 5月, 2009 2 次提交
    • T
      sched, timers: cleanup avenrun users · 2d02494f
      由 Thomas Gleixner 提交于 
      avenrun is an rough estimate so we don't have to worry about
consistency of the three avenrun values. Remove the xtime lock
dependency and provide a function to scale the values. Cleanup the
users.

[ Impact: cleanup ]
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
      2d02494f
    • T
      sched, timers: move calc_load() to scheduler · dce48a84
      由 Thomas Gleixner 提交于 
      Dimitri Sivanich noticed that xtime_lock is held write locked across
calc_load() which iterates over all online CPUs. That can cause long
latencies for xtime_lock readers on large SMP systems. 

The load average calculation is an rough estimate anyway so there is
no real need to protect the readers vs. the update. It's not a problem
when the avenrun array is updated while a reader copies the values.

Instead of iterating over all online CPUs let the scheduler_tick code
update the number of active tasks shortly before the avenrun update
happens. The avenrun update itself is handled by the CPU which calls
do_timer().

[ Impact: reduce xtime_lock write locked section ]
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
      dce48a84
  25. 13 5月, 2009 3 次提交
  27. 07 5月, 2009 1 次提交
    • D
      sched: emit thread info flags with stack trace · aa47b7e0
      由 David Rientjes 提交于 
      When a thread is oom killed and fails to exit, it's helpful to know which
threads have access to memory reserves if the machine livelocks.  This is
done by testing for the TIF_MEMDIE thread info flag and should be
displayed alongside stack traces to identify tasks that have access to
such reserves but are still stuck allocating pages, for instance.

It would probably be helpful in other cases as well, so all thread info
flags are emitted when showing a task.

( v2: fix warning reported by Stephen Rothwell )

[ Impact: extend debug printout info ]
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
LKML-Reference: <alpine.DEB.2.00.0905040136390.15831@chino.kir.corp.google.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      aa47b7e0
  29. 06 5月, 2009 2 次提交
  31. 05 5月, 2009 1 次提交
    • I
      perf_counter: initialize the per-cpu context earlier · 0d905bca
      由 Ingo Molnar 提交于 
      percpu scheduling for perfcounters wants to take the context lock,
but that lock first needs to be initialized. Currently it is an
early_initcall() - but that is too late, the task tick runs much
sooner than that.

Call it explicitly from the scheduler init sequence instead.

[ Impact: fix access-before-init crash ]

LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      0d905bca
  33. 29 4月, 2009 2 次提交
    • E
      sched: account system time properly · f5f293a4
      由 Eric Dumazet 提交于 
      Andrew Gallatin reported that IRQ and SOFTIRQ times were
sometime not reported correctly on recent kernels, and even
bisected to commit 457533a7
([PATCH] fix scaled & unscaled cputime accounting) as the first
bad commit.

Further analysis pointed that commit
79741dd3 ([PATCH] idle cputime
accounting) was the real cause of the problem.

account_process_tick() was not taking into account timer IRQ
interrupting the idle task servicing a hard or soft irq.

On mostly idle cpu, irqs were thus not accounted and top or
mpstat could tell user/admin that cpu was 100 % idle, 0.00 %
irq, 0.00 % softirq, while it was not.

[ Impact: fix occasionally incorrect CPU statistics in top/mpstat ]
Reported-by: NAndrew Gallatin <gallatin@myri.com>
Re-reported-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Acked-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Cc: rick.jones2@hp.com
Cc: brice@myri.com
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <49F84BC1.7080602@cosmosbay.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      f5f293a4
    • D
      sched: Document memory barriers implied by sleep/wake-up primitives · 50fa610a
      由 David Howells 提交于 
      Add a section to the memory barriers document to note the implied
memory barriers of sleep primitives (set_current_state() and wrappers)
and wake-up primitives (wake_up() and co.).

Also extend the in-code comments on the wake_up() functions to note
these implied barriers.

[ Impact: add documentation ]
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <20090428140138.1192.94723.stgit@warthog.procyon.org.uk>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      50fa610a