perf/core: Rewrite event timekeeping

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The current even timekeeping, which computes enabled and running
times, uses 3 distinct timestamps to reflect the various event states:
OFF (stopped), INACTIVE (enabled) and ACTIVE (running).

Furthermore, the update rules are such that even INACTIVE events need
their timestamps updated. This is undesirable because we'd like to not
touch INACTIVE events if at all possible, this makes event scheduling
(much) more expensive than needed.

Rewrite the timekeeping to directly use event->state, this greatly
simplifies the code and results in only having to update things when
we change state, or an up-to-date value is requested (read).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

...

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Peter Zijlstra 2017-09-05 14:16:28 +02:00 • committed by Ingo Molnar

parent 0c1cbc18df

commit 0d3d73aac2

2 changed files with 130 additions and 274 deletions

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include/linux/perf_event.h

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