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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140516153452.GM18551@zion.uk.xensource.com>
Date:	Fri, 16 May 2014 16:34:52 +0100
From:	Wei Liu <wei.liu2@...rix.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Wei Liu <wei.liu2@...rix.com>, <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, May 16, 2014 at 08:22:19AM -0700, Eric Dumazet wrote:
> 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)
> 

It works, at least in this Redis testcase. Could you explain a bit where
this 56000 magic number comes from? :-)

Presumably I can derive it from some constant in core network code?

Wei.

> 
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html