linux-kernel - documentation about scheduling policies

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Message-Id: <200809221729.06870.ms@teamix.de>
Date:	Mon, 22 Sep 2008 17:29:06 +0200
From:	Martin Steigerwald <ms@...mix.de>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>
Subject: documentation about scheduling policies

Please CC to me as I am not subscribed to linux-kernel.

Hi!

I wonder about scheduling policies in CFS. I find these:

ms@...go> grep "case SCHED_" sched.c sched_fair.c | sort | uniq 
~/lokal/Kernel/linux-2.6.26/kernel
sched.c:        case SCHED_BATCH:
sched.c:        case SCHED_FIFO:
sched.c:        case SCHED_IDLE:
sched.c:        case SCHED_NORMAL:
sched.c:        case SCHED_RR:

sched_fair.c seems to differentiate SCHED_PATCH only:

ms@...go> egrep "(SCHED_I|SCHED_B)" sched_fair.c                       
~/lokal/Kernel/linux-2.6.26/kernel
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
        if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) 
{
        if (unlikely(p->policy == SCHED_BATCH))

The documentation on scheduling policies in Documentation/scheduler appears 
rather scarse to me.

The wikipage at

http://ck.wikia.com/wiki/SchedulingPolicies

has more hints. But I wonder whether they are up to date and also they partly 
related to RSDL/SD features.

What about SCHED_IDLEPRIO anyway - the description of it makes it appear quite 
useful to me? Is it SCHED_IDLE in the new scheduler? Hmm, it does not appear 
that chrt can set this scheduling priority as of util-linux-ng 2.13.1.1.

I am willing to create documentation patches provided someone explains these 
to me ;-).

Ciao,
-- 
Martin Steigerwald - team(ix) GmbH - http://www.teamix.de
gpg: 19E3 8D42 896F D004 08AC A0CA 1E10 C593 0399 AE90

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