From 4a00c16e552ea5e71756cd29cd2df7557ec9cac4 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Thu, 3 Sep 2015 20:07:51 -0700 Subject: [PATCH] perf/core: Define PERF_PMU_TXN_READ interface 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 Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Michael Ellerman Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Link: http://lkml.kernel.org/r/1441336073-22750-9-git-send-email-sukadev@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 1 + kernel/events/core.c | 24 +++++++++++++++++++----- 2 files changed, 20 insertions(+), 5 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index ea3b5dd21a4c..b83cea932f74 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -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 diff --git a/kernel/events/core.c b/kernel/events/core.c index ade04dfab368..55b0f7cf2614 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -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 (event->state != PERF_EVENT_STATE_ACTIVE) + goto unlock; - if (!data->group) + 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); -- GitLab