From: German Gomez <german.gomez@arm.com>
To: Leo Yan <leo.yan@linaro.org>
Cc: Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
John Garry <john.garry@huawei.com>,
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,
James Clark <James.Clark@arm.com>
Subject: Re: [PATCH 4/5] perf arm-spe: Implement find_snapshot callback
Date: Fri, 15 Oct 2021 13:33:39 +0100 [thread overview]
Message-ID: <35209d5c-6387-5248-ab61-a1e1cb0553de@arm.com> (raw)
In-Reply-To: <20211013075125.GA6701@willie-the-truck>
Hi Leo,
Would you be ok with the current patch the way it is? In case it's of
any help, I'm sharing the testing steps that James and I went through
when testing this internally, if you want to add to it
- Test that only a portion of the buffer is saved until there is a wraparound
$ ./perf record -vvv -e arm_spe/period=148576/u -S -- taskset --cpu-list 0 stress --cpu 1 & while true; do sleep 0.2; killall -s USR2 perf; done
- Test snapshot mode in CPU mode
$ sudo ./perf record -vvv -C 0 -e arm_spe/period=148576/u -S -- taskset --cpu-list 0 stress --cpu 1 &
- Test that auxtrace buffers correspond to an aux record
- Test snapshot default sizes in sudo and user modes
- Test small snapshot size
$ ./perf record -vvv -e arm_spe/period=148576/u -S1000 -m16,16 -- taskset --cpu-list 0 stress --cpu 1 &
If there are any concerns with the patches, please let me know and I
will try to address them.
Thanks,
German
On 13/10/2021 08:51, Will Deacon wrote:
> On Wed, Oct 13, 2021 at 08:39:16AM +0800, Leo Yan wrote:
>> On Mon, Oct 11, 2021 at 04:55:37PM +0100, German Gomez wrote:
>>> On 06/10/2021 10:51, Leo Yan wrote:
>>>> On Wed, Oct 06, 2021 at 10:35:20AM +0100, German Gomez wrote:
>>>>
>>>> [...]
>>>>
>>>>>> So simply say, I think the head pointer monotonically increasing is
>>>>>> the right thing to do in Arm SPE driver.
>>>>> I will talk to James about how we can proceed on this.
>>>> Thanks!
>>> I took this offline with James and, though it looks possible to patch
>>> the SPE driver to have a monotonically increasing head pointer in order
>>> to simplify the handling in the perf tool, it could be a breaking change
>>> for users of the perf_event_open syscall that currently rely on the way
>>> it works now.
>> Here I cannot create the connection between AUX head pointer and the
>> breakage of calling perf_event_open().
>>
>> Could you elaborate what's the reason the monotonical increasing head
>> pointer will lead to the breakage for perf_event_open()?
> It's a user-visible change in behaviour, isn't it? Therefore we risk
> breaking applications that rely on the current behaviour if we change it
> unconditionally.
>
> Given that the driver has always worked like this and it doesn't sound like
> it's the end of the world to deal with it in userspace (after all, it's
> aligned with intel-pt), then I don't think we should change it.
>
> Will
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next prev parent reply other threads:[~2021-10-15 12:35 UTC|newest]
Thread overview: 38+ 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 ` [PATCH 2/5] perf arm-spe: " German Gomez
2021-09-23 13:35 ` Leo Yan
2021-09-16 15:46 ` [PATCH 3/5] perf arm-spe: Add snapshot mode support German Gomez
2021-10-20 12:48 ` Leo Yan
2021-09-16 15:46 ` [PATCH 4/5] perf arm-spe: Implement find_snapshot callback German Gomez
2021-09-23 13:50 ` Leo Yan
2021-09-23 14:40 ` Leo Yan
2021-09-30 12:26 ` German Gomez
2021-10-04 12:27 ` Leo Yan
2021-10-06 9:35 ` German Gomez
2021-10-06 9:51 ` Leo Yan
2021-10-11 15:55 ` German Gomez
2021-10-12 8:19 ` Will Deacon
2021-10-12 8:47 ` James Clark
2021-10-13 0:39 ` Leo Yan
2021-10-13 7:51 ` Will Deacon
2021-10-15 12:33 ` German Gomez [this message]
2021-10-15 14:16 ` Leo Yan
2021-10-15 14:41 ` German Gomez
2021-10-17 6:13 ` Leo Yan
2021-10-19 9:23 ` German Gomez
2021-10-19 13:12 ` Leo Yan
2021-11-02 11:02 ` German Gomez
2021-10-17 12:05 ` Leo Yan
2021-10-17 12:36 ` Leo Yan
2021-10-19 17:34 ` German Gomez
2021-10-20 13:25 ` Leo Yan
2021-09-16 15:46 ` [PATCH 5/5] perf arm-spe: Snapshot mode test German Gomez
2021-10-20 13:13 ` Leo Yan
2021-10-20 15:06 ` German Gomez
2021-11-02 14:07 ` James Clark
2021-11-02 15:37 ` James Clark
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 16:24 ` Mathieu Poirier
2021-09-30 12:09 ` German Gomez
2021-09-30 16:30 ` Mathieu Poirier
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