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Date: Tue, 17 Apr 2007 07:53:55 +0200
From: Willy Tarreau <w@1wt.eu>
To: Nick Piggin <npiggin@suse.de>
Cc: Peter Williams <pwil3058@bigpond.net.au>, Mike Galbraith <efault@gmx.de>,
       Con Kolivas <kernel@kolivas.org>, Ingo Molnar <mingo@elte.hu>,
       ck list <ck@vds.kolivas.org>, Bill Huey <billh@gnuppy.monkey.org>,
       linux-kernel@vger.kernel.org,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Arjan van de Ven <arjan@infradead.org>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]
Message-ID: <20070417055355.GQ943@1wt.eu>
References: <20070413202100.GA9957@elte.hu> <200704151327.13589.kernel@kolivas.org> <1176619384.6222.70.camel@Homer.simpson.net> <46240F98.3020800@bigpond.net.au> <1176776941.6222.21.camel@Homer.simpson.net> <20070417034050.GD25513@wotan.suse.de> <46244A52.4000403@bigpond.net.au> <20070417042954.GG25513@wotan.suse.de>
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Hi Nick,

On Tue, Apr 17, 2007 at 06:29:54AM +0200, Nick Piggin wrote:
(...)
> And my scheduler for example cuts down the amount of policy code and
> code size significantly. I haven't looked at Con's ones for a while,
> but I believe they are also much more straightforward than mainline...
> 
> For example, let's say all else is equal between them, then why would
> we go with the O(logN) implementation rather than the O(1)?

Of course, if this is the case, the question will be raised. But as a
general rule, I don't see much potential in O(1) to finely tune scheduling
according to several criteria. In O(logN), you can adjust scheduling in
realtime at a very low cost. Better processing of varying priorities or
fork() comes to mind.

Regards,
Willy