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

From: Metin Kaya <metin.kaya@arm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, John Stultz <jstultz@google.com>,
	Joel Fernandes <joelaf@google.com>,
	Qais Yousef <qyousef@google.com>, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Ben Segall <bsegall@google.com>,
	Zimuzo Ezeozue <zezeozue@google.com>,
	Youssef Esmat <youssefesmat@google.com>,
	Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Xuewen Yan <xuewen.yan94@gmail.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	kernel-team@android.com, linux-trace-kernel@vger.kernel.org
Subject: Re: [PATCH] sched: Add trace events for Proxy Execution (PE)
Date: Wed, 21 Feb 2024 14:24:59 +0000	[thread overview]
Message-ID: <10e83b13-bce5-4544-8923-1ee90a2135a8@arm.com> (raw)
In-Reply-To: <20240221092309.00432f37@gandalf.local.home>

On 21/02/2024 2:23 pm, Steven Rostedt wrote:
> On Fri,  2 Feb 2024 08:33:38 +0000
> Metin Kaya <metin.kaya@arm.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/
> 