[PATCH 0/6] perf core: Read from overwrite ring buffer

[Wang Nan <wangnan0@huawei.com>]

This is v2 of this series.

Compare with v1:

Fixes several bugs in v1.

Corresponsing perf has finished and can be found from:

 https://git.kernel.org/cgit/linux/kernel/git/pi3orama/linux.git/ 
 branch: perf/overwrite-benchmark

Some benchmarking results can be found from [1].

Summary:

On a PC with Intel E5-2640 0 @ 2.50GHz CPU, execute close(-1) 3000000
times, capture raw_syscalls:* with perf into overwrite ring buffer,
check total time (in us):

             MEAN           STDVAR
BASE     :  879870.81      11913.13
RAWPERF  : 2603854.7      706658.4
WRTBKWRD : 2313301.220      6727.957
TAILSIZE : 2383051.860      5248.061
RAWOVWRT : 2315273.180      5221.025
RAWOVWRT*: 2323970.45       5103.39 

Where:
BASE: don't use perf at all.
RAWPERF: use non-overwrite ring buffer, perf collects all data,
	 write to /dev/null
WRTBKWRD: Use backward writing ring buffer, write from tail to head,
          never wakeup perf, collect data when exiting.
TAILSIZE: Use tailsize ring buffer, pad 8 bytes for the size of the
          record for each event, never wakeup perf, collect data when
	  exiting.
RAWOVWRT: Use raw overwrite ring buffer, never wakeup perf, don't
          collect data at all.
RAWOVWRT*: Same as RAWOVWRT, without this patchset.

The benchmarking results shows WRTBKWRD is good enough. I suggest not
to implement TAILSIZE and tail-header ring buffer.

I will post the result on a smartphone next week.

[1] http://lkml.kernel.org/g/56A07FF3.2090009@huawei.com

Wang Nan (6):
  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 setting overwrite
    handler
  perf core: Put size of a sample at the end of it by
    PERF_SAMPLE_TAILSIZE

 include/linux/perf_event.h      |  39 +++++++---
 include/uapi/linux/perf_event.h |   7 +-
 kernel/events/core.c            | 155 +++++++++++++++++++++++++++++++---------
 kernel/events/internal.h        |  11 +++
 kernel/events/ring_buffer.c     |  70 +++++++++++++++---
 5 files changed, 228 insertions(+), 54 deletions(-)

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
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1.8.3.4