From: Bill Davidsen <davidsen@tmr.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Con Kolivas <kernel@kolivas.org>, linux-kernel@vger.kernel.org
Subject: Re: [patch] sched-2.6.0-test1-G6, interactivity changes
Date: Mon, 28 Jul 2003 17:38:16 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.3.96.1030728173045.19757A-100000@gatekeeper.tmr.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0307280921360.3537-100000@localhost.localdomain>
On Mon, 28 Jul 2003, Ingo Molnar wrote:
>
> On Mon, 28 Jul 2003, Con Kolivas wrote:
>
> > On Sun, 27 Jul 2003 23:40, Ingo Molnar wrote:
> > > - further increase timeslice granularity
> >
> > For a while now I've been running a 1000Hz 2.4 O(1) kernel tree that
> > uses timeslice granularity set to MIN_TIMESLICE which has stark
> > smoothness improvements in X. I've avoided promoting this idea because
> > of the theoretical drop in throughput this might cause. I've not been
> > able to see any detriment in my basic testing of this small granularity,
> > so I was curious to see what you throught was a reasonable lower limit?
>
> it's a hard question. The 25 msecs in -G6 is probably too low.
It would seem to me that the lower limit for a given CPU is a function of
CPU speed and cache size. One reason for longer slices is to preserve the
cache, but the real time to get good use from the cache is not a constant,
and you just can't pick any one number which won't be too short on a slow
cpu or unproductively long on a fast CPU. Hyperthreading shrinks the
effective cache size as well, but certainly not by 2:1 or anything nice.
Perhaps this should be a tunable set by a bit of hardware discovery at
boot and diddled at your own risk. Sure one factor in why people can't
agree on HZ and all to get best results.
--
bill davidsen <davidsen@tmr.com>
CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.
next prev parent reply other threads:[~2003-07-28 21:46 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-27 13:40 [patch] sched-2.6.0-test1-G6, interactivity changes Ingo Molnar
2003-07-27 14:03 ` Con Kolivas
2003-07-28 7:24 ` Ingo Molnar
2003-07-28 8:50 ` Con Kolivas
2003-07-28 21:38 ` Bill Davidsen [this message]
2003-07-28 22:00 ` Con Kolivas
2003-07-30 2:49 ` Bill Davidsen
2003-08-08 19:41 ` Rob Landley
2003-07-27 19:18 ` Felipe Alfaro Solana
2003-07-28 6:04 ` Mike Galbraith
2003-07-28 6:45 ` Andre Hedrick
2003-07-28 7:05 ` Con Kolivas
2003-07-28 7:33 ` Mike Galbraith
2003-07-28 7:44 ` Ingo Molnar
2003-07-30 14:24 ` Szonyi Calin
[not found] ` <Pine.LNX.4.44.0307280935300.4596-100000@localhost.localdom ain>
2003-07-28 8:15 ` Mike Galbraith
2003-07-28 8:42 ` Con Kolivas
2003-07-28 8:49 ` Mike Galbraith
[not found] ` <Pine.LNX.4.10.10307272338160.30891-100000@master.linux-ide .org>
2003-07-28 7:27 ` Mike Galbraith
2003-07-28 17:33 ` Andre Hedrick
[not found] ` <Pine.LNX.4.10.10307281030180.30891-100000@master.linux-ide .org>
2003-07-29 7:44 ` Mike Galbraith
2003-07-28 17:17 ` Jose Luis Domingo Lopez
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