linux-kernel - Re: Flash IO slow 1.5 MB/s

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Date:	Wed, 5 May 2010 10:14:58 +1000
From:	Dave Chinner <david@...morbit.com>
To:	"Trenton D. Adams" <trenton.d.adams@...il.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Flash IO slow 1.5 MB/s

On Mon, May 03, 2010 at 09:52:44PM -0600, Trenton D. Adams wrote:
> If I mount my usb key with "sync" option, I get 500kb or less transfer
> speeds.  If I use the gnome defaults, I get 60M+ for awhile, and then
> it continually drops over time, down to the 500kb/s again.  Gnome
> defaults are...
> 
> /dev/sdc1 on /media/FLASH type vfat
> (rw,nosuid,nodev,noatime,uhelper=hal,shortname=lower,flush,uid=500)
> 
> I have done similar tests on both Rally2 64G usb stick and sandisk
> ultra (15M/s) SDHC 8G cards.  I get lousy performance on both, unless
> I set dirty bytes.  These are both FAT 32.  But, as you can see below,
> 14 minutes to transfer less than a couple gigs is a little nutty.  The
> 3 minutes is a lot nicer.  I am using 2.6.33 with a patch from
> https://bugzilla.kernel.org/show_bug.cgi?id=15374

Perhaps it might be worth taking the writeback tracing code
from this patch series:

http://marc.info/?l=linux-fsdevel&m=127173141007222&w=2

And seeing what that tells you about how writeback is acting
differently....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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