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Message-ID: <f5b4e1e4-9966-c22a-1628-b3df37523841@intel.com>
Date: Tue, 20 Jun 2023 21:49:14 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Yang Jihong <yangjihong1@...wei.com>, peterz@...radead.org,
mingo@...hat.com, acme@...nel.org, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
namhyung@...nel.org, irogers@...gle.com,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] perf/core: deliver PERF_RECORD_COMM and
PERF_RECORD_MMAP side-band events to all online cpus
On 20/06/23 18:55, Yang Jihong wrote:
> Tasks are migrated between cores due to scheduling.
> If perf samples specified CPUs, PERF_RECORD_COMM and PERF_RECORD_MMAP
> events need be deliver to all cores to avoids the problem that the comm
> and symbols cannot be parsed due to task migration to the target core.
>
> The specific scenarios are as follows:
>
> CPU0 CPU1
> perf record -C 0 start
> taskA starts to be created and executed
> -> PERF_RECORD_COMM and PERF_RECORD_MMAP
> events only deliver to CPU1
> ......
> |
> migrate to CPU0
> |
> Running on CPU0 <----------/
> ...
>
> perf record -C 0 stop
>
> Now perf samples the PC of taskA. However, perf does not record the
> PERF_RECORD_COMM and PERF_RECORD_COMM events of taskA.
> Therefore, the comm and symbols of taskA cannot be parsed.
perf record deals with this for PERF_RECORD_TEXT_POKE, by opening
the corresponding "dummy" event on each CPU irrespective of whether
the main events are on selected CPUs. Refer
evlist__add_dummy_on_all_cpus().
So this could be handled by perf record.
>
> Yang Jihong (2):
> perf/core: perf_iterate_sb_cpu() supports to receive side-band events
> for all oneline cpus
> perf/core: deliver PERF_RECORD_COMM and PERF_RECORD_MMAP side-band
> events to all online cpus
>
> kernel/events/core.c | 58 +++++++++++++++++++++++++++++++-------------
> 1 file changed, 41 insertions(+), 17 deletions(-)
>
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