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* Re: [patch] 2.5.2 scheduler code for 2.4.18-pre1 ( was 2.5.2-pre performance degradation on an old 486 )
@ 2002-01-07  1:33 Mikael Pettersson
  2002-01-07  2:36 ` Davide Libenzi
  0 siblings, 1 reply; 10+ messages in thread
From: Mikael Pettersson @ 2002-01-07  1:33 UTC (permalink / raw)
  To: davidel; +Cc: axboe, linux-kernel, mjh, torvalds

On Sun, 6 Jan 2002 15:59:05 -0800 (PST), Davide Libenzi wrote:
>I made this patch for Andrea and it's the scheduler code for 2.4.18-pre1
>Could someone give it a try on old 486s

Done. On my '93 vintage 486, 2.4.18p1 + your scheduler results in very
bursty I/O and poor performance, just like I reported for 2.5.2-pre7.

/Mikael

^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: 2.5.2-pre performance degradation on an old 486
@ 2002-01-06 10:21 Jens Axboe
  2002-01-06 23:59 ` [patch] 2.5.2 scheduler code for 2.4.18-pre1 ( was 2.5.2-pre performance degradation on an old 486 ) Davide Libenzi
  0 siblings, 1 reply; 10+ messages in thread
From: Jens Axboe @ 2002-01-06 10:21 UTC (permalink / raw)
  To: Davide Libenzi; +Cc: Matthias Hanisch, Mikael Pettersson, Linus Torvalds, lkml

On Sat, Jan 05 2002, Davide Libenzi wrote:
> > > (*) 100MHz 486DX4, 28MB ram, no L2 cache, two old and slow IDE disks,
> > > small custom no-nonsense RedHat 7.2, kernels compiled with gcc 2.95.3.
> >
> > Is this ISA (maybe it has something to do with ISA bouncing)? Mine is:
> >
> > 486 DX/2 ISA, Adaptec 1542, two slow scsi disks and a self-made
> > slackware-based system.
> >
> > Can you also backout the scheduler changes to verify this? I have a
> > backout patch for 2.5.2-pre6, if you don't want to do this for yourself.
> 
> There should be some part of the kernel that assume a certain scheduler
> behavior. There was a guy that reported a bad  hdparm  performance and i
> tried it. By running  hdparm -t  my system has a context switch of 20-30
> and an irq load of about 100-110.
> The scheduler itself, even if you code it in visual basic, cannot make
> this with such loads.
> Did you try to profile the kernel ?

Davide,

If this is caused by ISA bounce problems, then you should be able to
reproduce by doing something ala

[ drivers/ide/ide-dma.c ]

ide_toggle_bounce()
{
	...

+	addr = BLK_BOUNCE_ISA;
	blk_queue_bounce_limit(&drive->queue, addr);
}

pseudo-diff, just add the addr = line. Now compare performance with and
without your scheduler changes.

-- 
Jens Axboe


^ permalink raw reply	[flat|nested] 10+ messages in thread
end of thread, other threads:[~2002-01-07 18:07 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2002-01-07  1:33 [patch] 2.5.2 scheduler code for 2.4.18-pre1 ( was 2.5.2-pre performance degradation on an old 486 ) Mikael Pettersson
2002-01-07  2:36 ` Davide Libenzi
2002-01-07  7:33   ` Jens Axboe
2002-01-07 18:12     ` Davide Libenzi
  -- strict thread matches above, loose matches on Subject: below --
2002-01-06 10:21 2.5.2-pre performance degradation on an old 486 Jens Axboe
2002-01-06 23:59 ` [patch] 2.5.2 scheduler code for 2.4.18-pre1 ( was 2.5.2-pre performance degradation on an old 486 ) Davide Libenzi
2002-01-07  1:38   ` Andrea Arcangeli
2002-01-07 14:35     ` J.A. Magallon
2002-01-07 14:37       ` Andrea Arcangeli
2002-01-07  7:32   ` Jens Axboe
2002-01-07 18:10     ` Davide Libenzi

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