Messages in this thread | | | Date | Wed, 12 Oct 2011 22:37:36 +0200 | Subject | Re: Oprofile Regression Caused by commit e5d1367f17ba6a6fed5fd8b74e4d5720923e0c25 on PPC | From | Stephane Eranian <> |
| |
Could be: a8d757e perf events: Fix slow and broken cgroup context switch code
On Wed, Oct 12, 2011 at 6:51 PM, Eric B Munson <emunson@mgebm.net> wrote: > 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 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |