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From: Frederic Weisbecker on 9 Jun 2010 23:50
In order to introduce new context exclusions, software events will
have to eventually stop when needed. We'll want perf_event_stop() to
act on every events.

To achieve this, remove the stub stop/start pmu callbacks of software
and tracepoint events.

This may even optimize the case of hardware and software events
running at the same time: now we only stop/start all hardware
events if we reset a hardware event period, not anymore with
software events.

Signed-off-by: Frederic Weisbecker <fweisbec(a)gmail.com>
Cc: Ingo Molnar <mingo(a)elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
Cc: Arnaldo Carvalho de Melo <acme(a)redhat.com>
Cc: Paul Mackerras <paulus(a)samba.org>
Cc: Stephane Eranian <eranian(a)google.com>
Cc: Cyrill Gorcunov <gorcunov(a)gmail.com>
Cc: Zhang Yanmin <yanmin_zhang(a)linux.intel.com>
Cc: Steven Rostedt <rostedt(a)goodmis.org>
---
kernel/perf_event.c | 29 ++++++++++++++++-------------
1 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index c772a3d..5c004f7 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1541,11 +1541,23 @@ static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count)
hwc->sample_period = sample_period;

if (local64_read(&hwc->period_left) > 8*sample_period) {
- perf_disable();
- perf_event_stop(event);
+ bool software_event = is_software_event(event);
+
+ /*
+ * Only hardware events need their irq period to be
+ * reprogrammed
+ */
+ if (!software_event) {
+ perf_disable();
+ perf_event_stop(event);
+ }
+
local64_set(&hwc->period_left, 0);
- perf_event_start(event);
- perf_enable();
+
+ if (!software_event) {
+ perf_event_start(event);
+ perf_enable();
+ }
}
}

@@ -4286,16 +4298,9 @@ static void perf_swevent_void(struct perf_event *event)
{
}

-static int perf_swevent_int(struct perf_event *event)
-{
- return 0;
-}
-
static const struct pmu perf_ops_generic = {
.enable = perf_swevent_enable,
.disable = perf_swevent_disable,
- .start = perf_swevent_int,
- .stop = perf_swevent_void,
.read = perf_swevent_read,
.unthrottle = perf_swevent_void, /* hwc->interrupts already reset */
};
@@ -4578,8 +4583,6 @@ static int swevent_hlist_get(struct perf_event *event)
static const struct pmu perf_ops_tracepoint = {
.enable = perf_trace_enable,
.disable = perf_trace_disable,
- .start = perf_swevent_int,
- .stop = perf_swevent_void,
.read = perf_swevent_read,
.unthrottle = perf_swevent_void,
};
--
1.6.2.3

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Prev: [PATCH 5/5] perf: Support for task/softirq/hardirq exclusion on tools
Next: [PATCH 5/12] scsi: megaraid_sas - Online Controller Reset (OCR): Add and initialize the OCR relaed variable