[lkml]   [2002]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: 2.5.2-pre performance degradation on an old 486
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 ?


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

[ drivers/ide/ide-dma.c ]


+ 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

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:15    [W:0.122 / U:0.376 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site