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

From: Wang Nan
Date: Fri Jan 22 2016 - 07:15:54 EST

This is v2 of this series.

Compare with v1:

Fixes several bugs in v1.

Corresponsing perf has finished and can be found from:

branch: perf/overwrite-benchmark

Some benchmarking results can be found from [1].


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):

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

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
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@xxxxxxxxxx

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
perf core: Put size of a sample at the end of it by

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@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