Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210528161552.654907-1-leo.yan@linaro.org> <CAOYpmdEvkSZaei-_SWrUC4YJ7rOUOoOaxM7+qc6dw=P+b_ivgA@mail.gmail.com>
 <5cf3effb-fccc-9385-6328-6d1e2e5ccdf3@arm.com> <CAOYpmdE=pSaDGOm+4iCh611DXVD766eCr5dACQ+TgOnSO=4EOA@mail.gmail.com>
 <20210612032721.GB36748@leoy-ThinkPad-X240s>
In-Reply-To: <20210612032721.GB36748@leoy-ThinkPad-X240s>
From:   Denis Nikitin <denik@google.com>
Date:   Sun, 20 Jun 2021 22:21:57 -1000
Message-ID: <CAOYpmdGW0U9u7zW3G6jyhZA23Uk1kd5gT00e9+g4O=k=WybDGA@mail.gmail.com>
Subject: Re: [PATCH v1 0/3] coresight: Fix for snapshot mode
To:     Leo Yan <leo.yan@linaro.org>
Cc:     Suzuki K Poulose <Suzuki.Poulose@arm.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Mike Leach <mike.leach@linaro.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        John Garry <john.garry@huawei.com>,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Daniel Kiss <daniel.kiss@arm.com>,
        Coresight ML <coresight@lists.linaro.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-perf-users@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Leo,

On Fri, Jun 11, 2021 at 5:27 PM Leo Yan <leo.yan@linaro.org> 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@arm.com> 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