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From: tip-bot for Matt Fleming <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: kanaka.d.juvva@intel.com, linux-kernel@vger.kernel.org,
	jolsa@redhat.com, acme@kernel.org, matt.fleming@intel.com,
	torvalds@linux-foundation.org, vikas.shivappa@linux.intel.com,
	acme@redhat.com, tglx@linutronix.de, mingo@kernel.org,
	hpa@zytor.com, peterz@infradead.org
Subject: [tip:perf/x86] perf: Add ->count() function to read per-package counters
Date: Wed, 25 Feb 2015 20:14:20 -0800	[thread overview]
Message-ID: <tip-eacd3ecc34472ce3751eedfc94e44c7cc6eb6305@git.kernel.org> (raw)
In-Reply-To: <1422038748-21397-3-git-send-email-matt@codeblueprint.co.uk>

Commit-ID:  eacd3ecc34472ce3751eedfc94e44c7cc6eb6305
Gitweb:     http://git.kernel.org/tip/eacd3ecc34472ce3751eedfc94e44c7cc6eb6305
Author:     Matt Fleming <matt.fleming@intel.com>
AuthorDate: Fri, 23 Jan 2015 18:45:41 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 25 Feb 2015 13:53:29 +0100

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>
---
 include/linux/perf_event.h | 10 ++++++++++
 kernel/events/core.c       |  5 ++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index cae4a94..9fc9b0d 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -272,6 +272,11 @@ struct pmu {
 	 */
 	size_t				task_ctx_size;
 
+
+	/*
+	 * Return the count value for a counter.
+	 */
+	u64 (*count)			(struct perf_event *event); /*optional*/
 };
 
 /**
@@ -770,6 +775,11 @@ static inline void perf_event_task_sched_out(struct task_struct *prev,
 		__perf_event_task_sched_out(prev, next);
 }
 
+static inline u64 __perf_event_count(struct perf_event *event)
+{
+	return local64_read(&event->count) + atomic64_read(&event->child_count);
+}
+
 extern void perf_event_mmap(struct vm_area_struct *vma);
 extern struct perf_guest_info_callbacks *perf_guest_cbs;
 extern int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
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)

  reply	other threads:[~2015-02-26  4:15 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-23 18:45 [PATCH v5 0/9] perf: Intel Cache QoS Monitoring support Matt Fleming
2015-01-23 18:45 ` [PATCH 1/9] perf: Make perf_cgroup_from_task() global Matt Fleming
2015-02-26  4:14   ` [tip:perf/x86] " tip-bot for Matt Fleming
2015-01-23 18:45 ` [PATCH 2/9] perf: Add ->count() function to read per-package counters Matt Fleming
2015-02-26  4:14   ` tip-bot for Matt Fleming [this message]
2015-01-23 18:45 ` [PATCH 3/9] perf: Move cgroup init before PMU ->event_init() Matt Fleming
2015-02-26  4:14   ` [tip:perf/x86] " tip-bot for Matt Fleming
2015-01-23 18:45 ` [PATCH 4/9] x86: Add support for Intel Cache QoS Monitoring (CQM) detection Matt Fleming
2015-02-26  4:14   ` [tip:perf/x86] x86: Add support for Intel Cache QoS Monitoring ( CQM) detection tip-bot for Peter P Waskiewicz Jr
2015-01-23 18:45 ` [PATCH 5/9] perf/x86/intel: Add Intel Cache QoS Monitoring support Matt Fleming
2015-01-25 18:34   ` Jiri Olsa
2015-01-25 23:07     ` Matt Fleming
2015-02-26  4:15   ` [tip:perf/x86] " tip-bot for Matt Fleming
2015-02-26 18:47     ` Matt Fleming
2015-02-26 19:40       ` Peter Zijlstra
2015-03-23 12:25       ` [tip:perf/x86] perf/x86/intel: Fix Makefile to actually build the cqm driver tip-bot for Matt Fleming
2015-01-23 18:45 ` [PATCH 6/9] perf/x86/intel: Implement LRU monitoring ID allocation for CQM Matt Fleming
2015-02-26  4:15   ` [tip:perf/x86] " tip-bot for Matt Fleming
2015-01-23 18:45 ` [PATCH 7/9] perf/x86/intel: Support task events with Intel CQM Matt Fleming
2015-02-26  4:15   ` [tip:perf/x86] " tip-bot for Matt Fleming
2015-03-04  4:16     ` Vince Weaver
2015-03-05  0:55       ` Ingo Molnar
2015-03-05 21:10         ` Peter Zijlstra
2015-03-23 12:26           ` [tip:perf/x86] perf: Remove type specific target pointers tip-bot for Peter Zijlstra
2015-01-23 18:45 ` [PATCH v5 8/9] perf/x86/intel: Perform rotation on Intel CQM RMIDs Matt Fleming
2015-02-26  4:16   ` [tip:perf/x86] " tip-bot for Matt Fleming
2015-01-23 18:45 ` [PATCH v5 9/9] perf/x86/intel: Enable conflicting event scheduling for CQM Matt Fleming
2015-02-26  4:16   ` [tip:perf/x86] " tip-bot for Matt Fleming

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