Subject: Re: Linux 2.6.8.1 CPU Scheduler Documentation
From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Willy Tarreau <willy@w.ods.org>
Cc: Josh Aas <josha@sgi.com>, linux-kernel@vger.kernel.org
In-Reply-To: <20050214052812.GA31941@alpha.home.local>
References: <420FEF73.30908@sgi.com>
	 <20050214052812.GA31941@alpha.home.local>
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Date: Mon, 14 Feb 2005 17:18:56 +1100
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On Mon, 2005-02-14 at 06:28 +0100, Willy Tarreau wrote:
> Hello Josh,
> 
> On Sun, Feb 13, 2005 at 06:23:15PM -0600, Josh Aas wrote:
> > Hello,
> > 
> > I have written an introduction to the Linux 2.6.8.1 CPU scheduler 
> > implementation. It should help people to understand what is going on in 
> > the scheduler code faster than they would be able to by just reading 
> > through the code. The paper can be downloaded in PDF or LyX form from 
> > here:
> > 
> > http://josh.trancesoftware.com/linux/
> 
> This is quite an interesting documentation.
> 

The multiprocessor scheduling documentation looks pretty
accurate, at a quick glance. A few small things though:

I don't think you place enough emphasis on the per-CPU-ness
of the 2.6 scheduler. For most workloads, this probably
yields by far the biggest improvement over the 2.4 scheduler
on even small SMP systems, due to much less lock and cacheline
contention.

Secondly, 7.1.2 can probably be removed completely. We can
actually handle this type of SMT balancing correctly without
shared runqueues (and in an arguably nicer way).

Nick


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