linux-kernel - Re: [Xen-devel] "tcp: refine TSO autosizing" causes performance regression on Xen

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Message-ID: <20150416042005.GA12179@gondor.apana.org.au>
Date:	Thu, 16 Apr 2015 12:20:06 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	stefano.stabellini@...citrix.com, george.dunlap@...citrix.com,
	Jonathan.Davies@...rix.com, xen-devel@...ts.xensource.com,
	wei.liu2@...rix.com, Ian.Campbell@...rix.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	edumazet@...gle.com, paul.durrant@...rix.com,
	christoffer.dall@...aro.org, felipe.franciosi@...rix.com,
	linux-arm-kernel@...ts.infradead.org, david.vrabel@...rix.com
Subject: Re: [Xen-devel] "tcp: refine TSO autosizing" causes performance
 regression on Xen

Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> We already have netdev->gso_max_size and netdev->gso_max_segs
> which are cached into sk->sk_gso_max_size & sk->sk_gso_max_segs

It is quite dangerous to attempt tricks like this because a
tc redirection or netfilter nat could change the destination
device rendering such hints incorrect.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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