summaryrefslogtreecommitdiffstats
path: root/kernel
diff options
context:
space:
mode:
authorMatt Fleming <matt.fleming@intel.com>2015-01-23 18:45:41 +0000
committerIngo Molnar <mingo@kernel.org>2015-02-25 13:53:29 +0100
commiteacd3ecc34472ce3751eedfc94e44c7cc6eb6305 (patch)
tree6a250e7e1c4b58cebeefc9be767479991d75ac9e /kernel
parent39bed6cbb842d8edf5a26b01122b391d36775b5e (diff)
downloadop-kernel-dev-eacd3ecc34472ce3751eedfc94e44c7cc6eb6305.zip
op-kernel-dev-eacd3ecc34472ce3751eedfc94e44c7cc6eb6305.tar.gz
perf: Add ->count() function to read per-package counters
For PMU drivers that record per-package counters, the ->count variable cannot be used to record an accurate aggregated value, since it's not possible to perform SMP cross-calls to cpus on other packages from the context in which we update ->count. Introduce a new optional ->count() accessor function that can be used to customize how values are collected. If a PMU driver doesn't provide a ->count() function, we fallback to the existing code. There is necessarily a window of staleness with this approach because the task that generated the counter value may not have been scheduled by the cpu recently. An alternative and more complex approach would be to use a hrtimer to periodically refresh the values from a more permissive scheduling context. So, we're trading off complexity for accuracy. Signed-off-by: Matt Fleming <matt.fleming@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kanaka Juvva <kanaka.d.juvva@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Vikas Shivappa <vikas.shivappa@linux.intel.com> Link: http://lkml.kernel.org/r/1422038748-21397-3-git-send-email-matt@codeblueprint.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 072de31..4e8dc59 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3194,7 +3194,10 @@ static void __perf_event_read(void *info)
static inline u64 perf_event_count(struct perf_event *event)
{
- return local64_read(&event->count) + atomic64_read(&event->child_count);
+ if (event->pmu->count)
+ return event->pmu->count(event);
+
+ return __perf_event_count(event);
}
static u64 perf_event_read(struct perf_event *event)
OpenPOWER on IntegriCloud