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Date: Sun, 11 Nov 2001 13:18:48 -0800 (PST)
From: Davide Libenzi <davidel@xmailserver.org>
X-X-Sender: davide@blue1.dev.mcafeelabs.com
To: Ingo Molnar <mingo@elte.hu>
cc: Mike Fedyk <mfedyk@matchmail.com>, Linus Torvalds <torvalds@transmeta.com>,
        lkml <linux-kernel@vger.kernel.org>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [patch] scheduler cache affinity improvement for 2.4 kernels
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Message-ID: <Pine.LNX.4.40.0111111308250.7269-100000@blue1.dev.mcafeelabs.com>
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On Fri, 9 Nov 2001, Ingo Molnar wrote:

>
> On Thu, 8 Nov 2001, Mike Fedyk wrote:
>
> > It remains to be proven whether the coarser scheduling approach
> > (Ingo's) will actually help when looking at cache properties.... [...]
>
> have you seen the numbers/measurements i posted in my original email? 3%
> kernel compile speedup on an 'idle' 8-way system, 7% compilation speedup
> with HZ=1024 and background networking load on a 1-way system.

Ingo, i'm giving the timer_ticks patch a try in my proposed scheduler coz
i like the idea of skipping the if inside goodness(), and i can do this
safely because inside the proposed scheduler i don't have any cross CPU
goodnesses ( no "if (p->processor != this_cpu) weight -= p->timer_ticks;" ).
I made a change to it anyway, that is adding a water-mark in the decay
behavior ( timer.c ).
When counter is above this watermark ( currently 20 ) the counter decay as
usual while if counter <= watermark, ticks accumulates in timer_ticks.
This solution keeps the same good behavior for CPU bound tasks while it
gives a "human"/current decay to tasks that has got a lot of counter
accumulation inside the recalc loop ( I/O bound ).




- Davide


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