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Groups > linux.kernel > #1312133
| From | Wang Nan <wangnan0@huawei.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 4/6] perf core: Add backwork attribute to perf event |
| Date | 2016-01-19 12:20 +0100 |
| Message-ID | <qSCun-6ZJ-25@gated-at.bofh.it> (permalink) |
| References | <qSgNb-rq-19@gated-at.bofh.it> <qSCum-6ZJ-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
In perf_event_attr a new bit 'write_backward' is appended to indicate
this event should write ring buffer from its end to beginning.
In perf_output_begin(), prepare ring buffer according this bit.
This patch introduces small overhead into perf_output_begin():
an extra memory read and a conditional branch. Further patch can remove
this overhead using custom output handler.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
include/linux/perf_event.h | 5 +++++
include/uapi/linux/perf_event.h | 3 ++-
kernel/events/core.c | 7 +++++++
kernel/events/ring_buffer.c | 2 ++
4 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f9828a4..54c3fb2 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1032,6 +1032,11 @@ static inline bool has_aux(struct perf_event *event)
return event->pmu->setup_aux;
}
+static inline bool is_write_backward(struct perf_event *event)
+{
+ return !!event->attr.write_backward;
+}
+
extern int perf_output_begin(struct perf_output_handle *handle,
struct perf_event *event, unsigned int size);
extern void perf_output_end(struct perf_output_handle *handle);
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 2c7f00c..598b9b0 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -340,7 +340,8 @@ struct perf_event_attr {
comm_exec : 1, /* flag comm events that are due to an exec */
use_clockid : 1, /* use @clockid for time fields */
context_switch : 1, /* context switch data */
- __reserved_1 : 37;
+ write_backward : 1, /* Write ring buffer from end to beginning */
+ __reserved_1 : 36;
union {
__u32 wakeup_events; /* wakeup every n events */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index f79c4be..8ad22a5 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8107,6 +8107,13 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
goto out;
/*
+ * Either writing ring buffer from beginning or from end.
+ * Mixing is not allowed.
+ */
+ if (is_write_backward(output_event) != is_write_backward(event))
+ goto out;
+
+ /*
* If both events generate aux data, they must be on the same PMU
*/
if (has_aux(event) && has_aux(output_event) &&
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index bbc3bc6..1372427 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -228,6 +228,8 @@ out:
int perf_output_begin(struct perf_output_handle *handle,
struct perf_event *event, unsigned int size)
{
+ if (unlikely(is_write_backward(event)))
+ return __perf_output_begin(handle, event, size, true);
return __perf_output_begin(handle, event, size, false);
}
--
1.8.3.4
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[PATCH] perf core: Introduce new ioctl options to pause and resume ring buffer Wang Nan <wangnan0@huawei.com> - 2016-01-18 13:00 +0100
Re: [PATCH] perf core: Introduce new ioctl options to pause and resume ring buffer Peter Zijlstra <peterz@infradead.org> - 2016-01-18 13:10 +0100
Re: [PATCH] perf core: Introduce new ioctl options to pause and resume ring buffer "Wangnan (F)" <wangnan0@huawei.com> - 2016-01-19 04:00 +0100
[PATCH 0/6] perf core: Read from overwrite ring buffer Wang Nan <wangnan0@huawei.com> - 2016-01-19 12:20 +0100
[PATCH 1/6] perf core: Introduce new ioctl options to pause and resume ring buffer Wang Nan <wangnan0@huawei.com> - 2016-01-19 12:20 +0100
[PATCH 6/6] perf/core: Put size of a sample at the end of it by PERF_SAMPLE_TAILSIZE Wang Nan <wangnan0@huawei.com> - 2016-01-19 12:20 +0100
[PATCH 2/6] perf core: Set event's default overflow_handler Wang Nan <wangnan0@huawei.com> - 2016-01-19 12:20 +0100
[PATCH 5/6] perf core: Reduce perf event output overhead by setting overwrite handler Wang Nan <wangnan0@huawei.com> - 2016-01-19 12:20 +0100
[PATCH 4/6] perf core: Add backwork attribute to perf event Wang Nan <wangnan0@huawei.com> - 2016-01-19 12:20 +0100
[PATCH 3/6] perf core: Prepare writing into ring buffer from end Wang Nan <wangnan0@huawei.com> - 2016-01-19 12:30 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer Namhyung Kim <namhyung@kernel.org> - 2016-01-19 15:10 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer pi3orama <pi3orama@163.com> - 2016-01-19 15:20 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-01-19 18:50 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer "Wangnan (F)" <wangnan0@huawei.com> - 2016-01-20 02:40 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-01-20 03:30 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer "Wangnan (F)" <wangnan0@huawei.com> - 2016-01-21 08:00 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer "Wangnan (F)" <wangnan0@huawei.com> - 2016-01-22 03:30 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-01-22 04:30 +0100
Re: [PATCH 0/6] perf core: Read from overwrite ring buffer "Wangnan (F)" <wangnan0@huawei.com> - 2016-01-22 05:50 +0100
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