Subject: Re: Limiting disk I/O?
To: None <tech-kern@NetBSD.org>
From: Joerg Sonnenberger <email@example.com>
Date: 11/13/2007 16:05:40
On Tue, Nov 13, 2007 at 09:36:22AM +0200, Jukka Marin wrote:
> On Tue, Nov 13, 2007 at 07:15:15AM +0000, Michael van Elst wrote:
> > >Wouldn't it be simpler to implement a new sysctl'able variable to limit the
> > >tps to some percentage of the disk I/O capacity?
> > The problem is not the disk. If you slow down the disk artificially
> > you just make the problem larger as you run out of buffers earlier.
> The disk is part of the problem, at least with twa. It seems the performance
> collapses when the controller becomes real busy. Even tw_cli (the 3ware cli
> tool) starts to crawl when softdep is pushing data to disk.
In that case the driver can do that completely internal.