Re: cfq misbehaving on 2.6.11-1.14_FC3

[Con Kolivas <kernel@kolivas.org>]

On Fri, 24 Jun 2005 04:30, spaminos-ker@yahoo.com wrote:
> --- Jens Axboe <axboe@suse.de> wrote:
> > Journalled file systems will behave worse for this, because it has to
> > tend to the journal as well. Can you try mounting that partition as ext2
> > and see what numbers that gives you?
>
> I did the tests again on a partition that I could mkfs/mount at will.
>
> On ext3, I get about 33 seconds average latency.
>
> And on ext2, as predicted, I have latencies in average of about 0.4
> seconds.
>
> I also tried reiserfs, and it gets about 22 seconds latency.
>
> As you pointed out, it seems that there is a flow in the way IO queues and
> journals (that are in some ways queues as well), interact in the presence
> of flushes.

I found the same, and the effect was blunted by noatime and 
journal_data_writeback (on ext3). Try them one at a time and see what you 
get.

Cheers,
Con

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