perf/x86/intel: Clean up LBR state tracking

Browse source

The lbr_context logic confused me; it appears to me to try and do the
same thing the pmu::sched_task() callback does now, but limited to
per-task events.

So rip it out. Afaict this should also improve performance, because I
think the current code can end up doing lbr_reset() twice, once from
the pmu::add() and then again from pmu::sched_task(), and MSR writes
(all 3*16 of them) are expensive!!

While thinking through the cases that need the reset it occured to me
the first install of an event in an active context needs to reset the
LBR (who knows what crap is in there), but detecting this case is
somewhat hard.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

...

This commit is contained in:

Peter Zijlstra 2016-07-07 19:37:52 +02:00 • committed by Ingo Molnar

parent a5dcff628a

commit 3e2c1a67d6

2 changed files with 29 additions and 29 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

57

arch/x86/events/intel/lbr.c

View file

1

arch/x86/events/perf_event.h

View file