Subject: Re: Limiting disk I/O?
To: Andrew Doran <>
From: Jukka Marin <>
List: tech-kern
Date: 11/13/2007 00:32:49
On Mon, Nov 12, 2007 at 09:07:34PM +0000, Andrew Doran wrote:
> This patch is against current but it should apply to netbsd-4, and I think
> it may help. If it doesn't apply it's easy to make the changes by hand:

Indeed, this helps to keep the disks accessible during high disk I/O - but
it also affects the performance provided by softdep.  Time to extract

- with softdep and the patch:
  2.073u 11.905s 3:02.38 7.6%     0+0k 895+24016io 0pf+0w

- without softdep:
  2.249u 10.499s 3:32.37 5.9%     0+0k 895+536917io 0pf+0w

With softdep, but without the patch, pkgsrc extract takes less than 14
seconds in case syncer does not kick in during the operation.

Well, there are many parameters to be tuned, better take a nap while the
system is doing a full build (with softdep and the patch).  Without the
patch the build (including X and creating ISO images) takes about 56 minutes.

Thanks for the suggestions - keep them coming ;-)  I'm interested in finding
out how to achieve the best disk performance.