I was tracking down some regressions in my perf_event_test testsuite.
Some of the tests broke in the 4.11-rc1 timeframe.
I've bisected one of them, this report is about
tests/overflow/simul_oneshot_group_overflow
This test creates an event group containing two sampling events, set
to overflow to a signal handler (which disables and then refreshes the
event).
On a good kernel you get the following:
Event perf::instructions with period 1000000
Event perf::instructions with period 2000000
fd 3 overflows: 946 (perf::instructions/1000000)
fd 4 overflows: 473 (perf::instructions/2000000)
Ending counts:
Count 0: 946379875
Count 1: 946365218
With the broken kernels you get:
Event perf::instructions with period 1000000
Event perf::instructions with period 2000000
fd 3 overflows: 938 (perf::instructions/1000000)
fd 4 overflows: 318 (perf::instructions/2000000)
Ending counts:
Count 0: 946373080
Count 1: 653373058
487f05e18aa4efacee6357480f293a5afe6593b5 is the first bad commit
commit 487f05e18aa4efacee6357480f293a5afe6593b5
Author: Alexander Shishkin <[email protected]>
Date: Thu Jan 19 18:43:30 2017 +0200
perf/core: Optimize event rescheduling on active contexts
When new events are added to an active context, we go and reschedule
all cpu groups and all task groups in order to preserve the priority
(cpu pinned, task pinned, cpu flexible, task flexible), but in
reality we only need to reschedule groups of the same priority as
that of the events being added, and below.
This patch changes the behavior so that only groups that need to be
rescheduled are rescheduled.
Reported-by: Adrian Hunter <[email protected]>
Signed-off-by: Alexander Shishkin <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: [email protected]
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
