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

From: Mark Rutland
Date: Mon Jun 19 2017 - 09:27:57 EST

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:
> >>
> >>
> >
> >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?