Re: [linux-usb-devel] System stalls using usb-storage

From: Matthew Dharm (mdharm-kernel@one-eyed-alien.net)
Date: Sun Jul 27 2003 - 01:35:45 EST

On Sun, Jul 27, 2003 at 08:24:44AM +0200, Oliver Neukum wrote:
> Am Donnerstag, 24. Juli 2003 05:00 schrieb Matthew Dharm:
> > Many people, including myself, have observed system stalls when using
> > usb-storage. It happens when copying large amounts of data to a USB device
> > -- everything (except the USB access) just stops for a little while. My
> > best guess is that the block cache is filling up (easy since USB is so
> > slow).
>
> Can you do a vmstat run? That should provide conclusive data.
> If so, write throteling is failing.

I'll set up some tests and get back to you...

> > The question is, what is the best way to handle this. I'm guessing that
> > increasing the priority of the usb-storage control thread will help, but
> > that's just a guess. I'm not even sure how to go about doing that, tho...
>
> A kernel thread in the block io path has to have a higher priority than
> any user task. Otherwise a priority inversion is possible.

Reasonable. So, other than renice at the command line, how does one go
about setting this?

Matt 

-- 
Matthew Dharm                              Home: mdharm-usb@one-eyed-alien.net 
Maintainer, Linux USB Mass Storage Driver

Somebody call an exorcist!
					-- Dust Puppy
User Friendly, 5/16/1998
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