From b83a46e7da4a948cc852ba7805dfb1a392dec861 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 8 Mar 2010 13:51:12 +0100 Subject: [PATCH] perf, x86: Don't reset the LBR as frequently If we reset the LBR on each first counter, simple counter rotation which first deschedules all counters and then reschedules the new ones will lead to LBR reset, even though we're still in the same task context. Reduce this by not flushing on the first counter but only flushing on different task contexts. Signed-off-by: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: paulus@samba.org Cc: eranian@google.com Cc: robert.richter@amd.com Cc: fweisbec@gmail.com LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index 0145f99f7a35..f278136bf918 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -72,12 +72,11 @@ static void intel_pmu_lbr_enable(struct perf_event *event) WARN_ON_ONCE(cpuc->enabled); /* - * Reset the LBR stack if this is the first LBR user or - * we changed task context so as to avoid data leaks. + * Reset the LBR stack if we changed task context to + * avoid data leaks. */ - if (!cpuc->lbr_users || - (event->ctx->task && cpuc->lbr_context != event->ctx)) { + if (event->ctx->task && cpuc->lbr_context != event->ctx) { intel_pmu_lbr_reset(); cpuc->lbr_context = event->ctx; } @@ -93,7 +92,7 @@ static void intel_pmu_lbr_disable(struct perf_event *event) return; cpuc->lbr_users--; - BUG_ON(cpuc->lbr_users < 0); + WARN_ON_ONCE(cpuc->lbr_users < 0); if (cpuc->enabled && !cpuc->lbr_users) __intel_pmu_lbr_disable(); -- GitLab