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;
Date:   Wed, 9 Jun 2021 09:39:09 +0800
From:   Leo Yan <leo.yan@linaro.org>
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        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>,
        Denis Nikitin <denik@google.com>, coresight@lists.linaro.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
Subject: Re: [PATCH v1 1/3] coresight: etm-perf: Correct buffer syncing for
 snapshot
Message-ID: <20210609013909.GE4640@leoy-ThinkPad-X240s>
References: <20210528161552.654907-1-leo.yan@linaro.org>
 <20210528161552.654907-2-leo.yan@linaro.org>
 <20210608214149.GA331611@p14s>
 <20210609013555.GD4640@leoy-ThinkPad-X240s>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20210609013555.GD4640@leoy-ThinkPad-X240s>
Precedence: bulk

On Wed, Jun 09, 2021 at 09:35:55AM +0800, Leo Yan wrote:

[...]

> > The problem with this approach is that if the AUX buffer is 4MB and the CS
> > buffer is 1MB then we only record 1MB, but because of N:1 topologies we may not
> > be able to do better.  I haven't looked at the code yet, something I will do
> > tomorrow.
> 
> Yes, the fixing in this patch copies the trace data is limited by the
> CoreSight bounce buffer length.  So if CoreSight buffer length is
> 1MiB, then we have no chance to allocate 4MiB for AUX buffer.

Sorry for typo, just correct:

if CoreSight buffer length is 1MiB, then we have no chance to *copy*
4MiB trace data for AUX buffer.