From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752083AbdGFJX3 (ORCPT ); Thu, 6 Jul 2017 05:23:29 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:34369 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750778AbdGFJX1 (ORCPT ); Thu, 6 Jul 2017 05:23:27 -0400 Message-ID: <1499333003.16045.15.camel@edumazet-glaptop3.roam.corp.google.com> Subject: Re: [PATCH net-next] skbuff: optimize the pull_pages code in __pskb_pull_tail() From: Eric Dumazet To: Lin Zhang Cc: davem@davemloft.net, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Date: Thu, 06 Jul 2017 02:23:23 -0700 In-Reply-To: <1499332587.16045.13.camel@edumazet-glaptop3.roam.corp.google.com> References: <1499331694-34678-1-git-send-email-xiaolou4617@gmail.com> <1499332587.16045.13.camel@edumazet-glaptop3.roam.corp.google.com> 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, 2017-07-06 at 02:16 -0700, Eric Dumazet wrote: > On Thu, 2017-07-06 at 17:01 +0800, Lin Zhang wrote: > > In the pull_pages code block, if the first frags size > eat, > > we can end the loop in advance to avoid extra copy. > > > > Signed-off-by: Lin Zhang > > --- > > net/core/skbuff.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > > index f990eb8..c00a1df 100644 > > --- a/net/core/skbuff.c > > +++ b/net/core/skbuff.c > > @@ -1720,6 +1720,10 @@ void *__pskb_pull_tail(struct sk_buff *skb, int delta) > > skb_shinfo(skb)->frags[k].page_offset += eat; > > skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat); > > eat = 0; > > + if (!i) { > > + k = skb_shinfo(skb)->nr_frags; > > + break; > > + } > > } > > k++; > > } > > 1) net-next is closed during merge window. > > 2) This change is completely buggy. > How have you tested it exactly ??? Hmm... it looks like I was wrong, but 1) still applies ;)