From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH 1/3] skb: Drop bad code from pskb_expand_head Date: Sun, 06 May 2012 13:13:37 -0400 (EDT) Message-ID: <20120506.131337.363109018749374511.davem@davemloft.net> References: <20120505001059.21292.31647.stgit@gitlad.jf.intel.com> <20120505002645.21292.38368.stgit@gitlad.jf.intel.com> <1336196130.3752.483.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: alexander.h.duyck@intel.com, netdev@vger.kernel.org, jeffrey.t.kirsher@intel.com To: eric.dumazet@gmail.com Return-path: Received: from shards.monkeyblade.net ([198.137.202.13]:41691 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754010Ab2EFRNk (ORCPT ); Sun, 6 May 2012 13:13:40 -0400 In-Reply-To: <1336196130.3752.483.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Date: Sat, 05 May 2012 07:35:30 +0200 > On Fri, 2012-05-04 at 17:26 -0700, Alexander Duyck wrote: >> The fast-path for pskb_expand_head contains a check where the size plus the >> unaligned size of skb_shared_info is compared against the size of the data >> buffer. This code path has two issues. First is the fact that after the >> recent changes by Eric Dumazet to __alloc_skb and build_skb the shared info >> is always placed in the optimal spot for a buffer size making this check >> unnecessary. The second issue is the fact that the check doesn't take into >> account the aligned size of shared info. As a result the code burns cycles >> doing a memcpy with nothing actually being shifted. >> >> Signed-off-by: Alexander Duyck ... > Acked-by: Eric Dumazet Applied.