Messages in this thread | | | Date | Thu, 14 Nov 2019 14:57:18 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v3 10/10] perf/cgroup: Do not switch system-wide events in cgroup switch |
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On Thu, Nov 14, 2019 at 08:46:51AM -0500, Liang, Kan wrote: > > > On 11/14/2019 5:43 AM, Peter Zijlstra wrote: > > On Wed, Nov 13, 2019 at 04:30:42PM -0800, Ian Rogers wrote: > > > From: Kan Liang <kan.liang@linux.intel.com> > > > > > > When counting system-wide events and cgroup events simultaneously, the > > > system-wide events are always scheduled out then back in during cgroup > > > switches, bringing extra overhead and possibly missing events. Switching > > > out system wide flexible events may be necessary if the scheduled in > > > task's cgroups have pinned events that need to be scheduled in at a higher > > > priority than the system wide flexible events. > > > > I'm thinking this patch is actively broken. groups->index 'group' wide > > and therefore across cpu/cgroup boundaries. > > > > There is no !cgroup to cgroup hierarchy as this patch seems to assume, > > specifically look at how the merge sort in visit_groups_merge() allows > > cgroup events to be picked before !cgroup events. > > > No, the patch intends to avoid switch !cgroup during cgroup context switch.
Which is wrong.
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