linux-kernel - Re: [PATCH 2/2] Customize sched domain via cpuset

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Message-Id: <1207125871.8514.755.camel@twins>
Date:	Wed, 02 Apr 2008 10:44:31 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Paul Jackson <pj@....com>
Subject: Re: [PATCH 2/2] Customize sched domain via cpuset

On Wed, 2008-04-02 at 17:41 +0900, Hidetoshi Seto wrote:
> Peter Zijlstra wrote:
> > On Tue, 2008-04-01 at 20:27 +0900, Hidetoshi Seto wrote:
> >> The implementation is here.
> >>
> >>  - Add 2 new cpuset files:
> >>      sched_wake_idle_far
> >>      sched_balance_newidle_far
> >>
> >>  - Modify partition_sched_domains() and build_sched_domains()
> >>    to take flags parameter passed from cpuset.
> >>
> >>  - Fill newidle_idx for node domains which currently unused but
> >>    might be required for sched_balance_newidle_far.
> > 
> > Just to be clear; the same effect can be had by poking into:
> > 
> >  /proc/sys/kernel/sched_domain/$cpu/$domain/flags
> > 
> > but this interface you now propose gives a more stable interface in that
> > you'd have to re-do your setting after every cpuset change (admittedly
> > those are rare, but I see how it could be a nuisance).
> 
> And the sysctl entry "sched_domain" is not available unless SCHED_DEBUG.
> 
> So it is common sense that this sysctl is not open to public yet,
> and that the expected users are scheduler developers, Ingo and friends.

Ah, right, totally forgot about that :-)

> > Or do you actually add something that wasn't available through the
> > initial domain interface?
> 
> At this time I have no idea, but it would be possible if there are
> something unreasonable on global system but acceptable on a part.
> 
> In other words, we can invent other sched_* families which has special
> effect that "default scheduler" never have.

I was asking about this patch in specific, and the answer seems to be:
no, we don't add anything that wasn't available.

And yes, I see the possiblilties to extend this :-)

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