lkml.org 
[lkml]   [2015]   [Sep]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:perf/core] perf/core: Define PERF_PMU_TXN_READ interface
Commit-ID:  4a00c16e552ea5e71756cd29cd2df7557ec9cac4
Gitweb: http://git.kernel.org/tip/4a00c16e552ea5e71756cd29cd2df7557ec9cac4
Author: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
AuthorDate: Thu, 3 Sep 2015 20:07:51 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 13 Sep 2015 11:27:28 +0200

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 <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>
---
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 ea3b5dd..b83cea9 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 ade04df..55b0f7c 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);

\
 
 \ /
  Last update: 2015-09-13 13:21    [W:0.256 / U:0.440 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site