perf_counter: Allow software counters to count while task is not running
commit880ca15adf2392770a68047e7a98e076ff4d21da
authorPaul Mackerras <paulus@samba.org>
Mon, 1 Jun 2009 07:49:14 +0000 (1 17:49 +1000)
committerIngo Molnar <mingo@elte.hu>
Mon, 1 Jun 2009 08:04:06 +0000 (1 10:04 +0200)
treea1707991a13651bcefb5d92a2ddee9b3470552d9
parent25346b93ca079080c9cb23331db5c4f6404e8530
perf_counter: Allow software counters to count while task is not running

This changes perf_swcounter_match() so that per-task software
counters can count events that occur while their associated
task is not running.  This will allow us to use the generic
software counter code for counting task migrations, which can
occur while the task is not scheduled in.

To do this, we have to distinguish between the situations where
the counter is inactive because its task has been scheduled
out, and those where the counter is inactive because it is part
of a group that was not able to go on the PMU.  In the former
case we want the counter to count, but not in the latter case.
If the context is active, we have the latter case.  If the
context is inactive then we need to know whether the counter
was counting when the context was last active, which we can
determine by comparing its ->tstamp_stopped timestamp with the
context's timestamp.

This also folds three checks in perf_swcounter_match, checking
perf_event_raw(), perf_event_type() and perf_event_id()
individually, into a single 64-bit comparison on
counter->hw_event.config, as an optimization.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <18979.34810.259718.955621@cargo.ozlabs.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
kernel/perf_counter.c