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authorAnton Blanchard <anton@samba.org>2011-01-17 05:17:42 (GMT)
committerIngo Molnar <mingo@elte.hu>2011-01-17 10:43:02 (GMT)
commit4bca770ede796a1ef7af9c983166d5608d9ccfaf (patch)
tree3a55c96dfb709415ee2c4e54e242c4f1a7cd01e2 /crypto/async_tx
parent7c46d8da09df22361d1d43465c4f1b06cecaf25f (diff)
downloadlinux-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 'crypto/async_tx')
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