[PATCH 0/2] patches to reduce perf overhead

[kan.liang@intel.com]

From: Kan Liang <kan.liang@intel.com>

perf brings additional overhead when monitoring the task which
frequently generates child task. Two of the related issues are fixed
in the patch series.

Here is some data from the overhead test on Broadwell server
  perf record -e $TEST_EVENTS -- ./loop.sh 50000

loop.sh
  start=$(date +%s%N)
  i=0
  while [ "$i" -le "$1" ]
  do
          date > /dev/null
          i=`expr $i + 1`
  done
  end=$(date +%s%N)
  elapsed=`expr $end - $start`

Event#	Original elapsed time	Elapsed time with two patches	delta
1	196,573,192,397		187,781,884,240			-4.47%
2	257,567,753,013		238,954,990,569			-7.23%
4	398,730,726,971		354,101,552,792			-11.19%
8	824,983,761,120		673,623,574,792			-18.35%
16	1,883,411,923,498	1,456,452,391,357		-22.67%

Kan Liang (2):
  perf,core: try parent pmu first when init child event
  perf,core: use parent avg sample period as child initial period

 include/linux/perf_event.h |  3 +++
 kernel/events/core.c       | 28 ++++++++++++++++++++++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

-- 
2.4.3