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sched/core: Move sched_entity::avg into separate cache line

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The sched_entity::avg collides with read-mostly sched_entity data.

The perf c2c tool showed many read HITM accesses across
many CPUs for sched_entity's cfs_rq and my_q, while having
at the same time tons of stores for avg.

After placing sched_entity::avg into separate cache line,
the perf bench sched pipe showed around 20 seconds speedup.

NOTE I cut out all perf events except for cycles and
instructions from following output.

Before:
  $ perf stat -r 5 perf bench sched pipe -l 10000000
  # Running 'sched/pipe' benchmark:
  # Executed 10000000 pipe operations between two processes

       Total time: 270.348 [sec]

        27.034805 usecs/op
            36989 ops/sec
   ...

     245,537,074,035      cycles                    #    1.433 GHz
     187,264,548,519      instructions              #    0.77  insns per cycle

       272.653840535 seconds time elapsed           ( +-  1.31% )

After:
  $ perf stat -r 5 perf bench sched pipe -l 10000000
  # Running 'sched/pipe' benchmark:
  # Executed 10000000 pipe operations between two processes

       Total time: 251.076 [sec]

        25.107678 usecs/op
            39828 ops/sec
  ...

     244,573,513,928      cycles                    #    1.572 GHz
     187,409,641,157      instructions              #    0.76  insns per cycle

       251.679315188 seconds time elapsed           ( +-  0.31% )

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Joe Mario <jmario@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/1449606239-28602-1-git-send-email-jolsa@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Jiri Olsa 2015-12-08 21:23:59 +01:00 committed by Ingo Molnar
parent 25ec02f2c1
commit 5a1078043f
1 changed files with 7 additions and 2 deletions
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9
include/linux/sched.h
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@ -1268,8 +1268,13 @@ struct sched_entity {
#endif
#ifdef CONFIG_SMP
/* Per entity load average tracking */
struct sched_avg avg;
/*
* Per entity load average tracking.
*
* Put into separate cache line so it does not
* collide with read-mostly values above.
*/
struct sched_avg avg ____cacheline_aligned_in_smp;
#endif
};