linux-kernel - Re: [RFC][PATCH] Multimedia scheduling class, take 2

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Message-ID: <4A0A0069.4090502@nortel.com>
Date:	Tue, 12 May 2009 17:04:09 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Jussi Laako <jussi@...arnerd.net>
CC:	Peter Zijlstra <peterz@...radead.org>,
	James Courtier-Dutton <James@...erbug.co.uk>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	d.faggioli@...up.it
Subject: Re: [RFC][PATCH] Multimedia scheduling class, take 2

Jussi Laako wrote:
> Chris Friesen wrote:
> 
>>Of course, without glibc/pthreads support you would only be able to set
>>the nice level for the current thread since you don't have any way to
>>map from "pthread_t *" to tid.  And you wouldn't be able to create new
>>threads with a particular nice level already set.
> 
> 
> This is the problem... It has to work this way, otherwise it's pretty
> useless.

Then you're hooped, because glibc checks for scheduler policies it
"knows" about.

>>But that argument
>>holds true for a new sched policy as well, because glibc checks the
>>policy internally and only knows about the normal three.
> 
> 
> Don't tell that to my system, where also SCHED_IDLE, SCHED_BATCH (which
> are btw not listed on POSIX either) ...and... SCHED_MM work. It goes
> directly to kernel which does the checks and fails if it sees fit.

Really?  You can call pthread_attr_setschedpolicy() with a policy of
SCHED_MM?  On my copy of glibc 2.8 it explicitly checks for
FIFO/RR/OTHER and anything else is rejected.

Chris
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