perf_counter: don't count scheduler ticks as context switches

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The context-switch software counter gives inflated values at present
because each scheduler tick and each process-wide counter
enable/disable prctl gets counted as a context switch.

This happens because perf_counter_task_tick, perf_counter_task_disable
and perf_counter_task_enable all call perf_counter_task_sched_out,
which calls perf_swcounter_event to record a context switch event.

This fixes it by introducing a variant of perf_counter_task_sched_out
with two underscores in front for internal use within the perf_counter
code, and makes perf_counter_task_{tick,disable,enable} call it.  This
variant doesn't record a context switch event, and takes a struct
perf_counter_context *.  This adds the new variant rather than
changing the behaviour or interface of perf_counter_task_sched_out
because that is called from other code.

[ Impact: fix inflated context-switch event counts ]

Signed-off-by: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <18951.48034.485580.498953@drongo.ozlabs.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

...

This commit is contained in:

Paul Mackerras 2009-05-11 15:46:10 +10:00 • committed by Ingo Molnar

parent 6751b71ea2

commit a08b159fc2

1 changed files with 11 additions and 5 deletions

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kernel/perf_counter.c

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