linux-kernel - Re: [RFC] perf migration

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Message-ID: <20100708071942.GA26454@elte.hu>
Date:	Thu, 8 Jul 2010 09:19:42 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tom Zanussi <tzanussi@...il.com>,
	Mike Galbraith <efault@....de>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Pierre Tardy <tardyp@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] perf migration


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> Hi,
> 
> To begin with, the name is a bit pompous. It's not a strong cpu task 
> migration observer as it's only based on the number of tasks living in a cpu 
> runqueue. This is the only basis for the cpu load: it doesn't handle the 
> nice level, scheduler classes, of each tasks (except idle ones that don't 
> count on the load).
> 
> At least not yet.
> 
> But still I think it's a cool toy, I've been playing with it for the last 
> weeks and it can give you a nice overview of what happens wrt migration 
> decisions for each migration opportunities: wake up, fork and exec, sleep 
> (sleep doesn't involve migration decision, but it's still an rq detach), and 
> load balancing. In fact it's more about "runqueue events".

Cool, looks really nice!

> == How to use ==
> 
> 
> I suggest you to use latest tip:/perf/core
> 
> Run the following command (followed by a command if you want):
> 
> $ sudo ./perf record -m 16384 -a -e sched:sched_wakeup -e sched:sched_wakeup_new -e sched:sched_switch -e sched:sched_migrate_task

Does 'perf sched record' include these events?

> Now ensure you have no lost events:
> 
> 
> $ sudo ./perf trace -d
> Misordered timestamps: 0
> Lost events: 0 <----

We need some warning for this in the GUI i guess?

> If so you need to increase the buffer size (-m nr_pages option in perf record).
> 
> Then put the script in the tools/perf directory and run it:
> 
> $ ./perf trace -s migration.py
> 
> You'll need wxpython.

Looks like this could be turned into 'perf sched view' or 'perf sched 
migration'?

How tasks schedule/migrate is basically how scheduler developers look at 
sched-trace data, so it would be nice if your GUI became the gui for perf 
sched.

	Ingo
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