[PATCH 0/5] perf core: Read from overwrite ring buffer

[Wang Nan]

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@xxxxxxxxxx

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@xxxxxxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Brendan Gregg <brendan.d.gregg@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx

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