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From: Herbert Xu <herbert@gondor.apana.org.au>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: stefano.stabellini@eu.citrix.com, george.dunlap@eu.citrix.com,
	Jonathan.Davies@citrix.com, xen-devel@lists.xensource.com,
	wei.liu2@citrix.com, Ian.Campbell@citrix.com,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	edumazet@google.com, paul.durrant@citrix.com,
	christoffer.dall@linaro.org, felipe.franciosi@citrix.com,
	linux-arm-kernel@lists.infradead.org, david.vrabel@citrix.com
Subject: Re: [Xen-devel] "tcp: refine TSO autosizing" causes performance regression on Xen
Date: Thu, 16 Apr 2015 12:20:06 +0800	[thread overview]
Message-ID: <20150416042005.GA12179@gondor.apana.org.au> (raw)
In-Reply-To: <1429121867.7346.136.camel@edumazet-glaptop2.roam.corp.google.com>

Eric Dumazet <eric.dumazet@gmail.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@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

WARNING: multiple messages have this Message-ID (diff)
From: herbert@gondor.apana.org.au (Herbert Xu)
To: linux-arm-kernel@lists.infradead.org
Subject: [Xen-devel] "tcp: refine TSO autosizing" causes performance regression on Xen
Date: Thu, 16 Apr 2015 12:20:06 +0800	[thread overview]
Message-ID: <20150416042005.GA12179@gondor.apana.org.au> (raw)
In-Reply-To: <1429121867.7346.136.camel@edumazet-glaptop2.roam.corp.google.com>

Eric Dumazet <eric.dumazet@gmail.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@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

  reply	other threads:[~2015-04-16  4:20 UTC|newest]

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-09 15:46 "tcp: refine TSO autosizing" causes performance regression on Xen Stefano Stabellini
2015-04-09 15:46 ` Stefano Stabellini
2015-04-09 15:46 ` Stefano Stabellini
2015-04-09 16:16 ` Eric Dumazet
2015-04-09 16:16   ` Eric Dumazet
2015-04-09 16:36   ` Stefano Stabellini
2015-04-09 16:36     ` Stefano Stabellini
2015-04-09 16:36     ` Stefano Stabellini
2015-04-09 17:07     ` Eric Dumazet
2015-04-09 17:07       ` Eric Dumazet
2015-04-13 10:56     ` [Xen-devel] " George Dunlap
2015-04-13 10:56       ` George Dunlap
2015-04-13 13:38       ` Jonathan Davies
2015-04-13 13:38         ` Jonathan Davies
2015-04-13 13:38         ` Jonathan Davies
2015-04-13 13:49       ` Eric Dumazet
2015-04-13 13:49         ` Eric Dumazet
2015-04-15 13:43         ` George Dunlap
2015-04-15 13:43           ` George Dunlap
2015-04-15 16:38           ` Eric Dumazet
2015-04-15 16:38             ` Eric Dumazet
2015-04-15 16:38             ` Eric Dumazet
2015-04-15 17:23             ` George Dunlap
2015-04-15 17:23               ` George Dunlap
2015-04-15 17:23               ` George Dunlap
2015-04-15 17:29               ` Eric Dumazet
2015-04-15 17:29                 ` Eric Dumazet
2015-04-15 17:41                 ` George Dunlap
2015-04-15 17:41                   ` George Dunlap
2015-04-15 17:41                   ` George Dunlap
2015-04-15 17:52                   ` Eric Dumazet
2015-04-15 17:52                     ` Eric Dumazet
2015-04-15 17:55                     ` Rick Jones
2015-04-15 17:55                       ` Rick Jones
2015-04-15 18:08                       ` Eric Dumazet
2015-04-15 18:08                         ` Eric Dumazet
2015-04-15 18:19                         ` Rick Jones
2015-04-15 18:19                           ` Rick Jones
2015-04-15 18:32                           ` Eric Dumazet
2015-04-15 18:32                             ` Eric Dumazet
2015-04-15 18:32                             ` Eric Dumazet
2015-04-15 20:08                             ` [Xen-devel] " Rick Jones
2015-04-15 20:08                               ` Rick Jones
2015-04-15 20:08                               ` Rick Jones
2015-04-15 18:04                     ` George Dunlap
2015-04-15 18:04                       ` George Dunlap
2015-04-15 18:04                       ` George Dunlap
2015-04-15 18:19                       ` Eric Dumazet
2015-04-15 18:19                         ` Eric Dumazet
2015-04-16  8:56                         ` George Dunlap
2015-04-16  8:56                           ` George Dunlap
2015-04-16  8:56                           ` George Dunlap
2015-04-16  9:20                           ` Daniel Borkmann
2015-04-16  9:20                             ` Daniel Borkmann
2015-04-16  9:20                             ` Daniel Borkmann
2015-04-16 10:01                             ` George Dunlap
2015-04-16 10:01                               ` George Dunlap
2015-04-16 10:01                               ` George Dunlap
2015-04-16 12:42                               ` Eric Dumazet
2015-04-16 12:42                                 ` Eric Dumazet
2015-04-20 11:03                                 ` George Dunlap
2015-04-20 11:03                                   ` George Dunlap
2015-06-02  9:52                                 ` Wei Liu
2015-06-02  9:52                                   ` Wei Liu
2015-06-02  9:52                                   ` Wei Liu
2015-06-02 16:16                                   ` Eric Dumazet
2015-06-02 16:16                                     ` Eric Dumazet
2015-04-16  9:22                           ` David Laight
2015-04-16  9:22                             ` David Laight
2015-04-16  9:22                             ` David Laight
2015-04-16 10:57                             ` George Dunlap
2015-04-16 10:57                               ` George Dunlap
2015-04-16 10:57                               ` George Dunlap
2015-04-15 17:41               ` Eric Dumazet
2015-04-15 17:41                 ` Eric Dumazet
2015-04-15 17:58                 ` Stefano Stabellini
2015-04-15 17:58                   ` Stefano Stabellini
2015-04-15 17:58                   ` Stefano Stabellini
2015-04-15 18:17                   ` Eric Dumazet
2015-04-15 18:17                     ` Eric Dumazet
2015-04-16  4:20                     ` Herbert Xu [this message]
2015-04-16  4:20                       ` Herbert Xu
2015-04-16  4:30                       ` Eric Dumazet
2015-04-16  4:30                         ` Eric Dumazet
2015-04-16 11:39                     ` George Dunlap
2015-04-16 11:39                       ` George Dunlap
2015-04-16 11:39                       ` George Dunlap
2015-04-16 12:16                       ` Eric Dumazet
2015-04-16 12:16                         ` Eric Dumazet
2015-04-16 13:00                       ` Tim Deegan
2015-04-16 13:00                         ` Tim Deegan
2015-04-16 13:00                         ` Tim Deegan

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