linux-kernel - Re: [PATCH 0/5] perf core: Read from overwrite ring buffer

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Date:	Tue, 26 Jan 2016 16:26:48 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	<peterz@...radead.org>
CC:	<alexei.starovoitov@...il.com>, <acme@...nel.org>,
	<linux-kernel@...r.kernel.org>, He Kuang <hekuang@...wei.com>,
	"Alexei Starovoitov" <ast@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Zefan Li <lizefan@...wei.com>, <pi3orama@....com>
Subject: Re: [PATCH 0/5] perf core: Read from overwrite ring buffer

Hi Peter,

Do you have any further comments about this patchset? What should be
the correct route for them to be merged into mainline?

Thank you.

On 2016/1/25 16:33, Wang Nan wrote:
> This is the v3 of this series. Compare with v2, tailsize method is
> removed, ioctl command PERF_EVENT_IOC_PAUSE_OUTPUT is changed to
> _IOW('$', 9, __u32) since it has an input value, commit message
> is slightly adjusted.
>
> New test result on ARM64 is below (x86_64 result is copied from previous
> email, test method is described in previous version [1]):
>
>                         x86_64        |       ARM64
>                -----------------------+---------------------
>                  MEAN         STDVAR  |    MEAN       STDVAR
>     BASE     :  879870.81   11913.13  |  808302.67   6951.47
>     RAWPERF  : 2603854.70  706658.40  | 3461675.12  54075.69
>     WRTBKWRD : 2313301.22    6727.96  | 3350177.98  23125.48
>     TAILSIZE : 2383051.86    5248.06  | 3556496.56  24802.17
>     RAWOVWRT : 2315273.18    5221.03  | 3458767.49  41560.32
>     RAWOVWRT*: 2323970.45    5103.39  | 3438967.06  34095.83
>
> ARM64 platform is a smartphone with 8 Hisilicon arm64 cores
> (big/little).
>
> Benckmarking result on both architechure support removing tailsize
> method because its performance penalty is higher than WRTBKWRD. Also, it
> seems we don't need to consider tailheader method (putting whole header
> at the end of records, kernel write to the ring buffer from beginning to
> end), because the above result shows WRTBKWRD and RAWOVWRT are similar,
> and tailheader is impossible to outperform RAWOVWRT in theory.
>
> [1] http://lkml.kernel.org/g/1453464834-233200-1-git-send-email-wangnan0@huawei.com
>
> Wang Nan (5):
>    perf core: Introduce new ioctl options to pause and resume ring buffer
>    perf core: Set event's default overflow_handler
>    perf core: Prepare writing into ring buffer from end
>    perf core: Add backward attribute to perf event
>    perf core: Reduce perf event output overhead by new overflow handler
>
>   include/linux/perf_event.h      | 22 +++++++++++--
>   include/uapi/linux/perf_event.h |  4 ++-
>   kernel/events/core.c            | 73 +++++++++++++++++++++++++++++++++++------
>   kernel/events/internal.h        | 11 +++++++
>   kernel/events/ring_buffer.c     | 63 +++++++++++++++++++++++++++++++----
>   5 files changed, 153 insertions(+), 20 deletions(-)
>
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: He Kuang <hekuang@...wei.com>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Brendan Gregg <brendan.d.gregg@...il.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
>