[maemo-users] Slow writes from linux to N900 in USB Mass Storage Mode

From: Paul Hartman paul.hartman+maemo at gmail.com
Date: Tue Jan 5 17:18:52 EET 2010
On Tue, Jan 5, 2010 at 5:32 AM, Timo Pelkonen <peltsip at gmail.com> wrote:
> 5. tammikuuta 2010 13.29 Kimmo Hämäläinen <kimmo.hamalainen at nokia.com>
> kirjoitti:
>> Hi,
>> On Sun, 2009-12-27 at 22:38 +0100, ext Paul Hartman wrote:
>> > Hi,
>> >
>> > I'm using linux kernel 2.6.32 on my PC and mount N900 in mass storage
>> > mode using vfat (async).
>> >
>> > If I write one file then sync/umount, write speed is about 17MB/sec,
>> > same as I get on Windows Vista. However, if I write more than one file
>> > and then sync/umount, speed is terrible, around 2MB/sec (and in kernel
>> > 2.6.31 that speed was about 450kb/sec using the old pdflush code). So
>> > it seems linux is maybe creating multiple write streams and N900
>> > doesn't deal with that well at all.
>> There has been some USB speed-ups since the sales release, but I'm not
>> sure if they fix this multiple file copying problem. I think it's best
>> to file a bug to maemo.org, so Maemo kernel guys get the word (I think
>> too few of them read this mailing list).
>> -Kimmo
>> > Size doesn't seem to matter, copying one 1gb file followed by sync is
>> > around 8 times faster than copying 2 500gb files followed by sync. In
>> > other words, as long as every single file copy is followed immediately
>> > by sync before moving on to the next file, speed is fine. If more than
>> > 1 file is copied before sync, it's bad.
>> >
>> > Does anyone else experience the same problem or have any ideas how to
>> > solve it? I'm no USB guru an every other USB device I have seems to
>> > work properly and at full speed. dmesg shows no messages (on PC) and
>> > it is running USB 2.0 etc.
>> >
>> > So far my only workaround is to copy/sync/copy/sync/copy/sync but
>> > that's annoying. However, the difference of taking 1 minute to write
>> > 1gb versus taking 20 minutes to write 1gb is also annoying.
>> >
>> > Thanks :)
> I suggest you try to change your settings in linux first
> http://talk.maemo.org/showpost.php?p=453521&postcount=24
> Ossipena / Timo

Thanks Timo, I actually wrote that post :) Sorry I forgot to follow-up here.

Yes, it seems CFQ for whatever reason is really slow with N900 (for
me). I don't know who is to "blame" (scheduler, vfat, n900, flash
memory, usb mass storage drivers...) but I'm happy to find a
work-around... and happy for modular i/o schedulers in linux :)

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