From: Steven Rostedt <rostedt@goodmis.org>
To: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: linux-kernel@vger.kernel.org, kcarcia@redhat.com,
Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Clark Willaims <williams@redhat.com>,
John Kacur <jkacur@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
linux-doc@vger.kernel.org
Subject: Re: [RFC PATCH 1/5] tracing/hwlat: Add a cpus file specific for hwlat_detector
Date: Thu, 15 Apr 2021 09:49:24 -0400 [thread overview]
Message-ID: <20210415094924.473a98df@gandalf.local.home> (raw)
In-Reply-To: <e5547e9a-d3d8-2cd1-7cb9-e567c798e78d@redhat.com>
On Thu, 15 Apr 2021 15:09:50 +0200
Daniel Bristot de Oliveira <bristot@redhat.com> wrote:
> But for the osnoise tracer the cpus file is really useful. For instance, on a
> system with the CPU 7 isolated:
>
> ----- %< -----
> # echo 7 > osnoise/cpus
> # echo target_cpu == 7 > events/sched/sched_wakeup/filter
> # echo stacktrace if target_cpu == 7 > events/sched/sched_wakeup/trigger
> # echo 1 > events/sched/sched_wakeup/enable
> # echo osnoise:thread_noise > set_event
> # echo osnoise > current_tracer
> # cat trace
> [find...]
> kworker/0:1-7 [000] d..5 1820.717780: <stack trace>
> => trace_event_raw_event_sched_wakeup_template
> => __traceiter_sched_wakeup
> => ttwu_do_wakeup
> => try_to_wake_up
> => __queue_work
> => queue_delayed_work_on
> => vmstat_shepherd
> => process_one_work
> => worker_thread
> => kthread
> => ret_from_fork
> kworker/7:1-410 [007] d..3 1820.717790: thread_noise: kworker/7:1:410 start 1820.717786519 duration 3626 ns
> osnoise/7-1000 [007] .... 1821.582340: 1000000 90 99.99100 15 1 0 12 6 1
> ----- >% -----
>
> It was possible to easily find that the '1' thread noise was a kworker,
> dispatched from CPU 0, and that it was dispatched by "vmstat_shepherd".
>
> Also, the osnoise dir is not added to a new instance... so, it only
> costs "one" file...
Every file counts. ;-)
What you did not articulate well, is that you want the other trace points
to be traced on all CPUs (maybe) when the osnoise threads are on a few (or
vice versa).
OK, for osnoise, I can see how it is useful. But as you said above, for
hwlat tracer, it's not as useful.
-- Steve
next prev parent reply other threads:[~2021-04-15 13:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-08 14:13 [RFC PATCH 0/5] hwlat improvements and osnoise tracer Daniel Bristot de Oliveira
2021-04-08 14:13 ` [RFC PATCH 1/5] tracing/hwlat: Add a cpus file specific for hwlat_detector Daniel Bristot de Oliveira
2021-04-14 14:10 ` Steven Rostedt
2021-04-15 13:09 ` Daniel Bristot de Oliveira
2021-04-15 13:49 ` Steven Rostedt [this message]
2021-04-15 14:33 ` Daniel Bristot de Oliveira
2021-04-08 14:13 ` [RFC PATCH 2/5] tracing/hwlat: Implement the mode config option Daniel Bristot de Oliveira
2021-04-14 14:30 ` Steven Rostedt
2021-04-15 13:16 ` Daniel Bristot de Oliveira
2021-04-15 13:50 ` Steven Rostedt
2021-04-08 14:13 ` [RFC PATCH 3/5] tracing/hwlat: Implement the per-cpu mode Daniel Bristot de Oliveira
2021-04-14 14:41 ` Steven Rostedt
2021-04-15 13:22 ` Daniel Bristot de Oliveira
2021-04-15 15:22 ` Steven Rostedt
2021-04-08 14:13 ` [RFC PATCH 4/5] tracing: Add __print_ns_to_secs() and __print_ns_without_secs() helpers Daniel Bristot de Oliveira
2021-04-08 14:13 ` [RFC PATCH 5/5] tracing: Add the osnoise tracer Daniel Bristot de Oliveira
2021-04-08 15:58 ` Jonathan Corbet
2021-04-09 7:19 ` Daniel Bristot de Oliveira
2021-04-14 17:14 ` Steven Rostedt
2021-04-15 13:43 ` Daniel Bristot de Oliveira
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