linux-kernel - Re: [PATCH] Scheduler: Improving the scheduler performance.

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Message-ID: <4619A101.5030600@redhat.com>
Date:	Sun, 08 Apr 2007 22:12:17 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Valdis.Kletnieks@...edu
CC:	root <swordfish@...tbd.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Scheduler: Improving the scheduler performance.

Valdis.Kletnieks@...edu wrote:
> On Sat, 07 Apr 2007 23:42:20 +0600, root said:
> 
>> As we know that, linux scheduler use separate runqueue for every CPU of
>> a multiprocessor system, which having an active and an expired array.If
>> we use only one expired array, then the CPUs of a multiprocessor system
>> will be able to share their expired task via the accumulated expired
>> array,
> 
> I got this far, and the first thought that popped into my head was:
> 
> "Wow.  This might actually win on a UP or small MP (2-15 CPU).  But the
> lock contention on a big 512-CPU machoflops box is likely going to *suck*".
> 
> For that matter, my quick eyeballing of the code, although it doesn't *find*
> any race conditions, doesn't convince me there's any protection taken to make
> sure there aren't any.  Is there some subtle algorithmic trick I'm missing
> to ensure Nothing Bad Can Happen?

Lock contention is going to be the least of your worries.

Destroying CPU affinity is the big one I suspect.

-- 
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