Messages in this thread | | | Date | Wed, 12 Oct 2011 12:51:54 -0400 | From | Eric B Munson <> | Subject | Re: Oprofile Regression Caused by commit e5d1367f17ba6a6fed5fd8b74e4d5720923e0c25 on PPC |
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On Tue, 11 Oct 2011, Peter Zijlstra wrote:
> On Mon, 2011-10-10 at 19:38 -0400, Eric B Munson wrote: > > On Fri, 07 Oct 2011, Eric B Munson wrote: > > > > > This commit seems to have caused a regression with oprofile. It is fairly easy > > > to trigger, simply run oprofile monitoring an event that will fire (something > > > frequent like CPU cycles) causes oprofile to fail saying that the PMU is in use. > > > If I disable CONFIG_CGROUP_PERF, everything goes back to working. I suspect the > > > problem is that the PMU is being initialized without being reserved for perf. I > > > am not yet sure of the right fix yet so if you have any suggestions I would > > > appreciate them. > > > > > > Eric > > > > This isn't the best description of the behavior we see, what happens is at some > > point in the profiling session the MMCR register is clobbered by > > perf_cgroup_switch() which calls perf_pmu_enable() without reserving the PMC > > hardware. When this happens oprofile stops counting. It doesn't happen each > > time so some runs show event counts that are reasonable, but it can also lead to > > event counts that are smaller than expected, or completely missing. > > What kernel are you testing? >
The problem seems to be fixed in 3.1-rc9 so I just need to identify the patch(es) that fixed it.
Eric [unhandled content-type:application/pgp-signature] | |