linux-kernel - Re: scheduler scalability - cgroups, cpusets and load-balancing

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Message-Id: <479F4E1A.BA47.005A.0@novell.com>
Date:	Tue, 29 Jan 2008 14:02:34 -0700
From:	"Gregory Haskins" <ghaskins@...ell.com>
To:	"Paul Jackson" <pj@....com>
Cc:	<a.p.zijlstra@...llo.nl>, <mingo@...e.hu>,
	<dmitry.adamushko@...il.com>, <rostedt@...dmis.org>,
	<menage@...gle.com>, <rientjes@...gle.com>, <tong.n.li@...el.com>,
	<tglx@...utronix.de>, <akpm@...ux-foundation.org>,
	<dhaval@...ux.vnet.ibm.com>, <vatsa@...ux.vnet.ibm.com>,
	<sgrubb@...hat.com>, <linux-kernel@...r.kernel.org>,
	<ebiederm@...ssion.com>, <nickpiggin@...oo.com.au>
Subject: Re: scheduler scalability - cgroups, cpusets and
	load-balancing

>>> On Tue, Jan 29, 2008 at  3:56 PM, in message
<20080129145647.579b7d53.pj@....com>, Paul Jackson <pj@....com> wrote: 
> Gregory wrote:
>> By moving it into the root_domain structure, there is now an instance
>> per (um, for lack of a better, more up to date word) "exclusive"
>> cpuset.   That way, disparate cpusets will not bother each other with
>> overload notifications, etc.
> 
> So the root_domain structure is meant to be the portions of the
> sched_domains that are shared across all CPUs in that sched_domain ?

Thats exactly right.

> 
> And the word 'cpuset', occurring in the above quote twice, should
> be 'sched_domain', right ?  Surely these aren't cpuset's ;).

Yeah, I think I am taking shortcuts in the language ;).  I wanted the root_domain to be an object of shared data that sits at the "root sched_domain", or in other terms the terminating parent in the hierarchy.  And there is one of these suckers created every time a non-overlapping cpuset is created (which was called "exclusive" at the time I wrote it, I believe, but I keep forgetting what you said they are called now ;).  So because the non-overlapping cpuset configuration begat the sched_domain hierarchy, I started using them interchangeably.  Sorry for the confusion :)

> 
> And 'exclusive cpuset' really means 'non-overlapping sched_domain' ?
> 
> Or am I still confused ?

No, I think you nailed it.

> 
> I would like to get our concepts clear, and terms consistent.  That's
> important for those others who would try to understand this.

Very good idea.  Thanks for doing this!

-Greg



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