Re: [gentoo-user] linux' IO performance sucks

["Richard Fish" <bigfish@asmallpond.org>]

On 7/4/06, Sven Köhler <skoehler@upb.de> wrote:
> So about every 200MB (i guess the linux box writes the data into the
> cache in the RAM first) linux writes the harddisk. But during that time
> - during the time it writes that 200MB to disk, there is no chance for
> any other IO. I'm playing an mp3 from the very same fileserver. It stops
> playing, because the machine does answer the read-requests.

What filesystem are you using?  I've seen this kind of behavior with
XFS, and the anticipatory scheduler, and solved it with the following
in my /etc/conf.d/local.start:

test -f /sys/block/sda/queue/iosched/antic_expire && \
    echo 0 >/sys/block/sda/queue/iosched/antic_expire
test -f /proc/sys/vm/laptop_mode && echo 0 >/proc/sys/vm/laptop_mode
test -f /proc/sys/fs/xfs/xfssyncd_centisecs && \
    echo 500 > /proc/sys/fs/xfs/xfssyncd_centisecs

You might also play with some of the other settings in
/proc/sys/fs/xfs and see what works for you.

Of course, if you are using a different filesystem or different
scheduler, it might help to know that.

-Richard

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