Re: [PATCH v1 0/3] coresight: Fix for snapshot mode

[Denis Nikitin]

Hi Leo,

On Fri, Jun 11, 2021 at 5:27 PM Leo Yan <leo.yan@xxxxxxxxxx> wrote:
>
> On Fri, Jun 11, 2021 at 01:31:41AM -0700, Denis Nikitin wrote:
> > Hi Suzuki,
> >
> > On Thu, Jun 10, 2021 at 9:04 AM Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> > >
> > [...]
> > >
> > > Are you able to confirm if the patch 3 alone fixes the above issue ?
> > > I am not convinced that Patch 1 is necessary.
> > >
> >
> > Yes. "perf cs-etm: Remove callback cs_etm_find_snapshot()" alone fixes
> > the issue.
>
> Based on current testing result, we should give high priority for
> patches 2 and 3.
>
> The patch 1 is controversial for how to handle the trace data kept
> in multiple AUX buffers; essentially it's up to how we understand the
> snapshot definition.  I confirmed Intel-PT and CoreSight have the same
> behaviour for capturing trace data from multiple AUX ring buffers when
> snapshot occurs.
>
> I'd like to leave patch 1/3 out, and resend it if we get conclusion.
> At the meantime, @Denis, if you have observed any profiling result
> (or profiling quality) difference caused by patch 1, the feedback would
> be very valuable.


I evaluated AutoFDO profiles with benchmarks but I was only focused
on the system-wide mode. And as I understood patch 1 fixes the issue
in non system-wide mode.
Currently I'm OoO so I won't be able to do further evaluation.

- Denis

>
>
> Thanks a lot for Denis' testing and insight review from Suzuki!
>
> Leo