Re: [PATCH v3 1/n] perf/core: addressing 4x slowdown during per-process profiling of STREAM benchmark on Intel Xeon Phi

[Alexey Budankov]

On 19.06.2017 18:14, Mark Rutland wrote:
> On Mon, Jun 19, 2017 at 04:37:41PM +0300, Alexey Budankov wrote:
> > On 19.06.2017 16:26, Mark Rutland wrote:
> > > On Mon, Jun 19, 2017 at 04:08:32PM +0300, Alexey Budankov wrote:
> > > > On 16.06.2017 1:10, Alexey Budankov wrote:
> > > > > On 15.06.2017 22:56, Mark Rutland wrote:
> > > > > > On Thu, Jun 15, 2017 at 08:41:42PM +0300, Alexey Budankov wrote:
> > > > > > > This series of patches continues v2 and addresses captured comments.
> > >
> > > > > > > Specifically this patch replaces pinned_groups and flexible_groups
> > > > > > > lists of perf_event_context by red-black cpu indexed trees avoiding
> > > > > > > data structures duplication and introducing possibility to iterate
> > > > > > > event groups for a specific CPU only.
> > >
> > > > > > Have you thrown Vince's perf fuzzer at this?
> > > > > >
> > > > > > If you haven't, please do. It can be found in the fuzzer directory of:
> > > > > >
> > > > > > https://github.com/deater/perf_event_tests
> > > > >
> > > > > Accepted.
> > > >
> > > > I run the test suite and it revealed no additional regressions in
> > > > comparison to what I have on the clean kernel.
> > > >
> > > > However the fuzzer constantly reports some strange stacks that are
> > > > not seen on the clean kernel and I have no idea how that might be
> > > > caused by the patches.
> > >
> > > Ok; that was the kind of thing I was concerned about.
> > >
> > > What you say "strange stacks", what do you mean exactly?
> > >
> > > I take it the kernel spewing backtraces in dmesg?
> > >
> > > Can you dump those?
> >
> > Here it is:
> >
> > list_del corruption. prev->next should be ffff88c2c4654010, but was
> > ffff88c31eb0c020
> > [  607.632813] ------------[ cut here ]------------
> > [  607.632816] kernel BUG at lib/list_debug.c:53!
>
> > [  607.635531] Call Trace:
> > [  607.635583]  list_del_event+0x1d7/0x210
>
> Given this patch changes how list_{del,add}_event() works, it's possible
> that this is a new bug.
>
> I was going to try to test this on arm64, but I couldn't get the patch
> to apply. I had a go with v4.12-rc5, tip/perf/core, and tip/perf/urgent.
>
> Which branch should I be using as the base?

v4.12-rc4+,
perf/core d0fabd1 [origin/perf/core] perf/core: Remove unused 
perf_cgroup_event_cgrp_time() function

> Thanks,
> Mark