From: Oliver Neukum <oliver@neukum.org>
To: Matthew Dharm <mdharm-kernel@one-eyed-alien.net>,
       USB Developers <linux-usb-devel@lists.sourceforge.net>,
       Kernel Developer List <linux-kernel@vger.kernel.org>
Subject: Re: [linux-usb-devel] System stalls using usb-storage
Date: Sun, 27 Jul 2003 08:24:44 +0200
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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.

> 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.

	Regards
		Oliver

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