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perf/core: Define PERF_PMU_TXN_READ interface

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Define a new PERF_PMU_TXN_READ interface to read a group of counters
at once.

        pmu->start_txn()                // Initialize before first event

        for each event in group
                pmu->read(event);       // Queue each event to be read

        rc = pmu->commit_txn()          // Read/update all queued counters

Note that we use this interface with all PMUs.  PMUs that implement this
interface use the ->read() operation to _queue_ the counters to be read
and use ->commit_txn() to actually read all the queued counters at once.

PMUs that don't implement PERF_PMU_TXN_READ ignore ->start_txn() and
->commit_txn() and continue to read counters one at a time.

Thanks to input from Peter Zijlstra.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.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: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
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>
Link: http://lkml.kernel.org/r/1441336073-22750-9-git-send-email-sukadev@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Sukadev Bhattiprolu 2015-09-03 20:07:51 -07:00 committed by Ingo Molnar
parent 7d88962e23
commit 4a00c16e55
2 changed files with 21 additions and 6 deletions
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1
include/linux/perf_event.h
View File

@ -202,6 +202,7 @@ struct perf_event;
#define PERF_EVENT_TXN 0x1
#define PERF_PMU_TXN_ADD 0x1 /* txn to add/schedule event on PMU */
#define PERF_PMU_TXN_READ 0x2 /* txn to read event group from PMU */
/**
* pmu::capabilities flags

26
kernel/events/core.c
View File

@ -3199,6 +3199,7 @@ static void __perf_event_read(void *info)
struct perf_event *sub, *event = data->event;
struct perf_event_context *ctx = event->ctx;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
struct pmu *pmu = event->pmu;
/*
* If this is a task context, we need to check whether it is
@ -3217,18 +3218,31 @@ static void __perf_event_read(void *info)
}
update_event_times(event);
if (event->state == PERF_EVENT_STATE_ACTIVE)
event->pmu->read(event);
if (!data->group)
if (event->state != PERF_EVENT_STATE_ACTIVE)
goto unlock;
if (!data->group) {
pmu->read(event);
data->ret = 0;
goto unlock;
}
pmu->start_txn(pmu, PERF_PMU_TXN_READ);
pmu->read(event);
list_for_each_entry(sub, &event->sibling_list, group_entry) {
update_event_times(sub);
if (sub->state == PERF_EVENT_STATE_ACTIVE)
if (sub->state == PERF_EVENT_STATE_ACTIVE) {
/*
* Use sibling's PMU rather than @event's since
* sibling could be on different (eg: software) PMU.
*/
sub->pmu->read(sub);
}
}
data->ret = 0;
data->ret = pmu->commit_txn(pmu);
unlock:
raw_spin_unlock(&ctx->lock);