linux-kernel - Re: [PATCH] sched: Add trace events for Proxy Execution (PE)

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Message-ID: <10e83b13-bce5-4544-8923-1ee90a2135a8@arm.com>
Date: Wed, 21 Feb 2024 14:24:59 +0000
From: Metin Kaya <metin.kaya@....com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, John Stultz <jstultz@...gle.com>,
 Joel Fernandes <joelaf@...gle.com>, Qais Yousef <qyousef@...gle.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Valentin Schneider <vschneid@...hat.com>,
 Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Ben Segall <bsegall@...gle.com>, Zimuzo Ezeozue <zezeozue@...gle.com>,
 Youssef Esmat <youssefesmat@...gle.com>, Mel Gorman <mgorman@...e.de>,
 Daniel Bristot de Oliveira <bristot@...hat.com>,
 Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
 Boqun Feng <boqun.feng@...il.com>, "Paul E. McKenney" <paulmck@...nel.org>,
 Xuewen Yan <xuewen.yan94@...il.com>, K Prateek Nayak
 <kprateek.nayak@....com>, Thomas Gleixner <tglx@...utronix.de>,
 kernel-team@...roid.com, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: Add trace events for Proxy Execution (PE)

On 21/02/2024 2:23 pm, Steven Rostedt wrote:
> On Fri,  2 Feb 2024 08:33:38 +0000
> Metin Kaya <metin.kaya@....com> wrote:
> 
>> Add sched_[start, finish]_task_selection trace events to measure the
>> latency of PE patches in task selection.
>>
>> Moreover, introduce trace events for interesting events in PE:
>> 1. sched_pe_enqueue_sleeping_task: a task gets enqueued on wait queue of
>>     a sleeping task (mutex owner).
>> 2. sched_pe_cross_remote_cpu: dependency chain crosses remote CPU.
>> 3. sched_pe_task_is_migrating: mutex owner task migrates.
>>
>> New trace events can be tested via this command:
>> $ perf trace \
>>    -e sched:sched_start_task_selection \
>>    -e sched:sched_finish_task_selection \
>>    -e sched:sched_pe_enqueue_sleeping_task \
>>    -e sched:sched_pe_cross_remote_cpu \
>>    -e sched:sched_pe_task_is_migrating
>>
>> Notes:
>> 1. These trace events are not intended to merge upstream. Instead, they
>>     are only for making PE tests easier and will be converted to trace
>>     points once PE patches hit upstream.
> 
> I wonder if the tracepoints should be added though? That is, not adding the
> trace_events that show up in tracefs, but just the tracepoints so that bpf
> or local modules could hook to them?

Yep, the intention is providing necessary support for modules (e.g., 
https://github.com/ARM-software/lisa/blob/main/lisa/_assets/kmodules/lisa/tp.c). 

> 
> -- Steve
> 
> 
>> 2. This patch is based on John's Proxy Execution v7 patch series (see
>>     the link below) which is also available at
>>     https://github.com/johnstultz-work/linux-dev/commits/proxy-exec-v7-6.7-rc6/.
>>
>> Link: https://lore.kernel.org/linux-kernel/CANDhNCrHd+5twWVNqBAhVLfhMhkiO0KjxXBmwVgaCD4kAyFyWw@mail.gmail.com/
>