Messages in this thread Patch in this message | | | Date | Wed, 27 May 2015 03:03:49 -0700 | From | tip-bot for Thomas Gleixner <> | Subject | [tip:perf/core] perf/x86/intel/cqm: Avoid pointless MSR write |
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Commit-ID: 0bac237845e203dd1439cfc571b1baf1b2274b3b Gitweb: http://git.kernel.org/tip/0bac237845e203dd1439cfc571b1baf1b2274b3b Author: Thomas Gleixner <tglx@linutronix.de> AuthorDate: Tue, 19 May 2015 00:00:55 +0000 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 27 May 2015 09:17:40 +0200
perf/x86/intel/cqm: Avoid pointless MSR write
If the usage counter is non-zero there is no point to update the rmid in the PQR MSR.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Matt Fleming <matt.fleming@intel.com> Cc: Kanaka Juvva <kanaka.d.juvva@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Vikas Shivappa <vikas.shivappa@linux.intel.com> Cc: Will Auld <will.auld@intel.com> Link: http://lkml.kernel.org/r/20150518235150.080844281@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/kernel/cpu/perf_event_intel_cqm.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_cqm.c b/arch/x86/kernel/cpu/perf_event_intel_cqm.c index 63391f8..2ce69c0 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_cqm.c +++ b/arch/x86/kernel/cpu/perf_event_intel_cqm.c @@ -974,10 +974,12 @@ static void intel_cqm_event_start(struct perf_event *event, int mode) event->hw.cqm_state &= ~PERF_HES_STOPPED; - if (state->cnt++) - WARN_ON_ONCE(state->rmid != rmid); - else + if (state->cnt++) { + if (!WARN_ON_ONCE(state->rmid != rmid)) + return; + } else { WARN_ON_ONCE(state->rmid); + } state->rmid = rmid; /*
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