From: Robert Hancock <hancockr@shaw.ca>
To: Alex Bennee <kernel-hacker@bennee.com>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: DMA not working on SATA?
Date: Wed, 26 Mar 2008 23:20:18 -0600 [thread overview]
Message-ID: <47EB2E92.9060401@shaw.ca> (raw)
In-Reply-To: <fa.tM6egqVO3jg78PMZEi2Ne7NkjtI@ifi.uio.no>
Alex Bennee wrote:
> Hi,
>
> Since I got my new machine I noticed it seemed to be running slower than
> I expected for a duel core machine including a lot of stuttering. After
> tweaking the BIOS settings from "Legacy" to "AHCI" I measured a doubling
> of read performance with hdparm but heavy IO still makes the machine
> sluggish, with top showing ~80% of the time in the wait state (and
> loadavg shooting up). This seems like a DMA problem because I was under
> the impression a task demanding IO should be able to sleep on a DMA
> completion rather than blocking everything else.
That's not what IOwait means. It basically means "nothing better to do
than wait for IO to complete". If you have only one running task which
is blocked waiting for IO you will always have high IOwait.
next parent reply other threads:[~2008-03-27 5:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <fa.tM6egqVO3jg78PMZEi2Ne7NkjtI@ifi.uio.no>
2008-03-27 5:20 ` Robert Hancock [this message]
2008-03-27 10:00 ` DMA not working on SATA? Alex Bennee
2008-03-27 17:45 ` Roger Heflin
2008-03-26 9:59 Alex Bennee
2008-03-26 9:56 ` Alan Cox
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