From: German Gomez <german.gomez@arm.com>
To: Leo Yan <leo.yan@linaro.org>
Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
John Garry <john.garry@huawei.com>, Will Deacon <will@kernel.org>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Mike Leach <mike.leach@linaro.org>,
linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org
Subject: Re: [PATCH 4/5] perf arm-spe: Implement find_snapshot callback
Date: Thu, 30 Sep 2021 13:26:15 +0100 [thread overview]
Message-ID: <1c6a3a73-27dc-6673-7fe7-34bc7fcb0a68@arm.com> (raw)
In-Reply-To: <20210923144048.GB603008@leoy-ThinkPad-X240s>
Hi Leo,
On 23/09/2021 15:40, Leo Yan wrote:
> On Thu, Sep 23, 2021 at 09:50:16PM +0800, Leo Yan wrote:
>
> [...]
>
>>> @@ -336,6 +480,7 @@ struct auxtrace_record *arm_spe_recording_init(int *err,
>>> sper->itr.pmu = arm_spe_pmu;
>>> sper->itr.snapshot_start = arm_spe_snapshot_start;
>>> sper->itr.snapshot_finish = arm_spe_snapshot_finish;
>>> + sper->itr.find_snapshot = arm_spe_find_snapshot;
>> If I understand correctly, this patch copies the code from cs-etm for
>> snapshot handling. About 2 months ago, we removed the Arm cs-etm's
>> specific snapshot callback function and directly use perf's function
>> __auxtrace_mmap__read() to handle 'head' and 'tail' pointers. Please
>> see the commit for details:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2f01c200d4405c4562e45e8bb4de44a5ce37b217
>>
>> Before I review more details for snapshot enabling in patches 03 and
>> 04, could you confirm if Arm SPE can use the same way with cs-etm for
>> snapshot handling? From my understanding, this is a better way to
>> handle AUX buffer's 'head' and 'tail'.
> In other words, if we can only apply patch 03 and can pass the testing
> in patch 05, then it would be a very neat implementation.
>
> I will try to verify these patches and will get back result.
>
> Thanks,
> Leo
The patch is indeed based on that commit. The reason behind it is that the
values for *head are being wrapped in the driver side (see the macro
PERF_IDX2OFF which is used at various points in
/drivers/perf/arm_spe_pmu.c).
If this callback is not to be added, I believe the driver needs to be
updated
first so that the head pointer monotonically increases like in cs-etm.
Do you
think this makes sense for SPE?
(note that the patch will skip the wrap-around detection if this is the
case,
in order to handle both cases in the userspace perf tool).
Thanks,
German
WARNING: multiple messages have this Message-ID (diff)
From: German Gomez <german.gomez@arm.com>
To: Leo Yan <leo.yan@linaro.org>
Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
John Garry <john.garry@huawei.com>, Will Deacon <will@kernel.org>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Mike Leach <mike.leach@linaro.org>,
linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org
Subject: Re: [PATCH 4/5] perf arm-spe: Implement find_snapshot callback
Date: Thu, 30 Sep 2021 13:26:15 +0100 [thread overview]
Message-ID: <1c6a3a73-27dc-6673-7fe7-34bc7fcb0a68@arm.com> (raw)
In-Reply-To: <20210923144048.GB603008@leoy-ThinkPad-X240s>
Hi Leo,
On 23/09/2021 15:40, Leo Yan wrote:
> On Thu, Sep 23, 2021 at 09:50:16PM +0800, Leo Yan wrote:
>
> [...]
>
>>> @@ -336,6 +480,7 @@ struct auxtrace_record *arm_spe_recording_init(int *err,
>>> sper->itr.pmu = arm_spe_pmu;
>>> sper->itr.snapshot_start = arm_spe_snapshot_start;
>>> sper->itr.snapshot_finish = arm_spe_snapshot_finish;
>>> + sper->itr.find_snapshot = arm_spe_find_snapshot;
>> If I understand correctly, this patch copies the code from cs-etm for
>> snapshot handling. About 2 months ago, we removed the Arm cs-etm's
>> specific snapshot callback function and directly use perf's function
>> __auxtrace_mmap__read() to handle 'head' and 'tail' pointers. Please
>> see the commit for details:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2f01c200d4405c4562e45e8bb4de44a5ce37b217
>>
>> Before I review more details for snapshot enabling in patches 03 and
>> 04, could you confirm if Arm SPE can use the same way with cs-etm for
>> snapshot handling? From my understanding, this is a better way to
>> handle AUX buffer's 'head' and 'tail'.
> In other words, if we can only apply patch 03 and can pass the testing
> in patch 05, then it would be a very neat implementation.
>
> I will try to verify these patches and will get back result.
>
> Thanks,
> Leo
The patch is indeed based on that commit. The reason behind it is that the
values for *head are being wrapped in the driver side (see the macro
PERF_IDX2OFF which is used at various points in
/drivers/perf/arm_spe_pmu.c).
If this callback is not to be added, I believe the driver needs to be
updated
first so that the head pointer monotonically increases like in cs-etm.
Do you
think this makes sense for SPE?
(note that the patch will skip the wrap-around detection if this is the
case,
in order to handle both cases in the userspace perf tool).
Thanks,
German
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-09-30 12:26 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-16 15:46 [PATCH 1/5] perf cs-etm: Print size using consistent format German Gomez
2021-09-16 15:46 ` German Gomez
2021-09-16 15:46 ` [PATCH 2/5] perf arm-spe: " German Gomez
2021-09-16 15:46 ` German Gomez
2021-09-23 13:35 ` Leo Yan
2021-09-23 13:35 ` Leo Yan
2021-09-16 15:46 ` [PATCH 3/5] perf arm-spe: Add snapshot mode support German Gomez
2021-09-16 15:46 ` German Gomez
2021-10-20 12:48 ` Leo Yan
2021-10-20 12:48 ` Leo Yan
2021-09-16 15:46 ` [PATCH 4/5] perf arm-spe: Implement find_snapshot callback German Gomez
2021-09-16 15:46 ` German Gomez
2021-09-23 13:50 ` Leo Yan
2021-09-23 13:50 ` Leo Yan
2021-09-23 14:40 ` Leo Yan
2021-09-23 14:40 ` Leo Yan
2021-09-30 12:26 ` German Gomez [this message]
2021-09-30 12:26 ` German Gomez
2021-10-04 12:27 ` Leo Yan
2021-10-04 12:27 ` Leo Yan
2021-10-06 9:35 ` German Gomez
2021-10-06 9:35 ` German Gomez
2021-10-06 9:51 ` Leo Yan
2021-10-06 9:51 ` Leo Yan
2021-10-11 15:55 ` German Gomez
2021-10-11 15:55 ` German Gomez
2021-10-12 8:19 ` Will Deacon
2021-10-12 8:19 ` Will Deacon
2021-10-12 8:47 ` James Clark
2021-10-12 8:47 ` James Clark
2021-10-13 0:39 ` Leo Yan
2021-10-13 0:39 ` Leo Yan
2021-10-13 7:51 ` Will Deacon
2021-10-13 7:51 ` Will Deacon
2021-10-15 12:33 ` German Gomez
2021-10-15 12:33 ` German Gomez
2021-10-15 14:16 ` Leo Yan
2021-10-15 14:16 ` Leo Yan
2021-10-15 14:41 ` German Gomez
2021-10-15 14:41 ` German Gomez
2021-10-17 6:13 ` Leo Yan
2021-10-17 6:13 ` Leo Yan
2021-10-19 9:23 ` German Gomez
2021-10-19 9:23 ` German Gomez
2021-10-19 13:12 ` Leo Yan
2021-10-19 13:12 ` Leo Yan
2021-11-02 11:02 ` German Gomez
2021-11-02 11:02 ` German Gomez
2021-10-17 12:05 ` Leo Yan
2021-10-17 12:05 ` Leo Yan
2021-10-17 12:36 ` Leo Yan
2021-10-17 12:36 ` Leo Yan
2021-10-19 17:34 ` German Gomez
2021-10-19 17:34 ` German Gomez
2021-10-20 13:25 ` Leo Yan
2021-10-20 13:25 ` Leo Yan
2021-09-16 15:46 ` [PATCH 5/5] perf arm-spe: Snapshot mode test German Gomez
2021-09-16 15:46 ` German Gomez
2021-10-20 13:13 ` Leo Yan
2021-10-20 13:13 ` Leo Yan
2021-10-20 15:06 ` German Gomez
2021-10-20 15:06 ` German Gomez
2021-11-02 14:07 ` James Clark
2021-11-02 14:07 ` James Clark
2021-11-02 15:37 ` James Clark
2021-11-02 15:37 ` James Clark
2021-11-09 13:26 ` German Gomez
2021-11-09 13:26 ` German Gomez
2021-09-23 13:35 ` [PATCH 1/5] perf cs-etm: Print size using consistent format Leo Yan
2021-09-23 13:35 ` Leo Yan
2021-09-23 16:24 ` Mathieu Poirier
2021-09-23 16:24 ` Mathieu Poirier
2021-09-30 12:09 ` German Gomez
2021-09-30 12:09 ` German Gomez
2021-09-30 16:30 ` Mathieu Poirier
2021-09-30 16:30 ` Mathieu Poirier
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