From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752395AbbDPEbH (ORCPT ); Thu, 16 Apr 2015 00:31:07 -0400 Received: from mail-pa0-f49.google.com ([209.85.220.49]:34709 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750755AbbDPEbA (ORCPT ); Thu, 16 Apr 2015 00:31:00 -0400 Message-ID: <1429158657.7346.160.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: [Xen-devel] "tcp: refine TSO autosizing" causes performance regression on Xen From: Eric Dumazet To: Herbert Xu 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 Date: Wed, 15 Apr 2015 21:30:57 -0700 In-Reply-To: <20150416042005.GA12179@gondor.apana.org.au> References: <20150416042005.GA12179@gondor.apana.org.au> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2015-04-16 at 12:20 +0800, Herbert Xu wrote: > Eric Dumazet 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. Right but we are talking of performance hints, on quite basic VM setup. Here the guest would use xen and this hint would apply. From mboxrd@z Thu Jan 1 00:00:00 1970 From: eric.dumazet@gmail.com (Eric Dumazet) Date: Wed, 15 Apr 2015 21:30:57 -0700 Subject: [Xen-devel] "tcp: refine TSO autosizing" causes performance regression on Xen In-Reply-To: <20150416042005.GA12179@gondor.apana.org.au> References: <20150416042005.GA12179@gondor.apana.org.au> Message-ID: <1429158657.7346.160.camel@edumazet-glaptop2.roam.corp.google.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, 2015-04-16 at 12:20 +0800, Herbert Xu wrote: > Eric Dumazet 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. Right but we are talking of performance hints, on quite basic VM setup. Here the guest would use xen and this hint would apply.