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author | Anton Blanchard <anton@samba.org> | 2011-01-17 05:17:42 (GMT) |
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committer | Ingo Molnar <mingo@elte.hu> | 2011-01-17 10:43:02 (GMT) |
commit | 4bca770ede796a1ef7af9c983166d5608d9ccfaf (patch) | |
tree | 3a55c96dfb709415ee2c4e54e242c4f1a7cd01e2 /tools | |
parent | 7c46d8da09df22361d1d43465c4f1b06cecaf25f (diff) | |
download | linux-fsl-qoriq-4bca770ede796a1ef7af9c983166d5608d9ccfaf.tar.xz |
powerpc: perf: Fix frequency calculation for overflowing counters
When profiling a benchmark that is almost 100% userspace, I noticed some wildly
inaccurate profiles that showed almost all time spent in the kernel.
Closer examination shows we were programming a tiny number of cycles into the
PMU after each overflow (about ~200 away from the next overflow). This gets us
stuck in a loop which we eventually break out of by throttling the PMU (there
are regular throttle/unthrottle events in the log).
It looks like we aren't setting event->hw.last_period to something same and the
frequency to period calculations in perf are going haywire.
With the following patch we find the correct period after a few interrupts and
stay there. I also see no more throttle events.
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
LKML-Reference: <20110117161742.5feb3761@kryten>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'tools')
0 files changed, 0 insertions, 0 deletions