netdev - Re: [PATCH net-next] xen-netfront: try linearizing SKB if it occupies too many slots

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Date:	Fri, 16 May 2014 08:22:19 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Wei Liu <wei.liu2@...rix.com>
Cc:	netdev@...r.kernel.org, xen-devel@...ts.xen.org,
	David Vrabel <david.vrabel@...rix.com>,
	Konrad Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Stefan Bader <stefan.bader@...onical.com>,
	Zoltan Kiss <zoltan.kiss@...rix.com>
Subject: Re: [PATCH net-next] xen-netfront: try linearizing SKB if it
 occupies too many slots

On Fri, 2014-05-16 at 15:36 +0100, Wei Liu wrote:
> On Fri, May 16, 2014 at 07:21:08AM -0700, Eric Dumazet wrote:
> > On Fri, 2014-05-16 at 14:11 +0100, Wei Liu wrote:
> > 
> > > It's not that common to trigger this, I only saw a few reports. In fact
> > > Stefan's report is the first one that comes with a method to reproduce
> > > it.
> > > 
> > > I tested with redis-benchmark on a guest with 256MB RAM and only saw a
> > > few "failed to linearize", never saw a single one with 1GB guest.
> > 
> > Well, I am just saying. This is asking order-5 allocations, and yes,
> > this is going to fail after few days of uptime, no matter what you try.
> > 
> 
> Hmm... I see what you mean -- memory fragmentation leads to allocation
> failure. Thanks.

In the mean time, have you tried to lower gso_max_size ?

Setting it witk netif_set_gso_max_size() to something like 56000 might
avoid the problem.

(Not sure if it is applicable in your case)



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