linux-kernel - Re: [RFC] Scheduler recorder and playback

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Date:	Thu, 08 Mar 2012 16:20:05 +0100
From:	Stephan Bärwolf 
	<stephan.baerwolf@...ilmenau.de>
To:	linux-kernel@...r.kernel.org
CC:	linaro-kernel@...ts.linaro.org, panto@...oniou-consulting.com
Subject: Re: [RFC] Scheduler recorder and playback

Hi Pantelis,

what is your primary goal?

Saving power? Improving interactivity? Be more cache-optimal?

I think recording the scheduling (without drastically slowing it down) is hard to do,
since it ticks at least HZ times per second.

Replay such an recording (on a differeny platform) seems even harder to me.
Since different cpus (and number of them), different speed and a very likely not
reproduceable process-setup may noise completely the replay.

Do you also want to record/replay the behaviour of the more important loadbalancer, too?

Did you thought to compare different platforms by simply having syntetically generated
loads? (I.e. see interbench -> http://users.on.net/~ckolivas/interbench/)

If you are interested in examing the scheduling-behaviour as a function of the tuneables
(and even the HZ) - and if you are interested in getting better latency, maybe you
are interested in nitro-patch for the scheduler?
(I currently don't have an external patch-file, but you can get it integrated from
https://github.com/baerwolf/linux-stephan/commits/v3.2.9-stephan-201203030000 )

Nitro enables you to do so some things, like:

        * tune the scheduler at configuration point
        * increase the ticker-frequency way above 1000Hz
        * tune the ticker-freq. from userspace during runtime
	* change the scheduling-algo for idle-tasks

regards Stephan
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