linux-kernel - Re: USBFS Memory allocation Bug

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Message-Id: <20100314193114.619a2616.akpm@linux-foundation.org>
Date:	Sun, 14 Mar 2010 19:31:14 -0400
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Mel Gorman <mel@....ul.ie>,
	Markus Rechberger <mrechberger@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, Greg KH <greg@...ah.com>
Subject: Re: USBFS Memory allocation Bug

On Thu, 11 Mar 2010 11:56:22 -0500 (EST) Alan Stern <stern@...land.harvard.edu> wrote:

> On Wed, 10 Mar 2010, Mel Gorman wrote:
> 
> > > > Is there any means for the driver to take the large request, break it up
> > > > into multiple smaller requests and submit them one at a time?
> > > 
> > > In theory almost anything is possible.  But it would be a big effort
> > > and not consistent with the way the rest of the driver works.
> > > 
> > 
> > Then about the only other suggestion would be a mempool containing a small
> > number of largest-possible buffers that is enabled if there is no swap
> > available.
> 
> Considering that this is the first report I have heard about this sort 
> of problem, and that adding swap space would probably fix it, I'm not 
> inclined to make any changes.

Adding swap space is unlikely to help here.  For an order-6 allocation
the page allocator will go into wtf-youre-kidding-me mode and won't
even bother trying.

Asking the allocator for 2^6 physically contiguous pages is terribly
unreliable and shouldn't be done by any kernel code which wants to be
useful.


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