From 09e61b4f78498bd9f213b0a536e80b79507ea89f Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 6 Jul 2016 18:02:43 +0200 Subject: perf/x86/intel: Rework the large PEBS setup code In order to allow optimizing perf_pmu_sched_task() we must ensure perf_sched_cb_{inc,dec}() are no longer called from NMI context; this means that pmu::{start,stop}() can no longer use them. Prepare for this by reworking the whole large PEBS setup code. The current code relied on the cpuc->pebs_enabled state, however since that reflects the current active state as per pmu::{start,stop}() we can no longer rely on this. Introduce two counters: cpuc->n_pebs and cpuc->n_large_pebs which count the total number of PEBS events and the number of PEBS events that have FREERUNNING set, resp.. With this we can tell if the current setup requires a single record interrupt threshold or can use a larger buffer. This also improves the code in that it re-enables the large threshold once the PEBS event that required single record gets removed. Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- kernel/events/core.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'kernel/events') diff --git a/kernel/events/core.c b/kernel/events/core.c index 11f6bbe..57aff71 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2818,6 +2818,10 @@ void perf_sched_cb_inc(struct pmu *pmu) /* * This function provides the context switch callback to the lower code * layer. It is invoked ONLY when the context switch callback is enabled. + * + * This callback is relevant even to per-cpu events; for example multi event + * PEBS requires this to provide PID/TID information. This requires we flush + * all queued PEBS records before we context switch to a new task. */ static void perf_pmu_sched_task(struct task_struct *prev, struct task_struct *next, -- cgit v1.1