From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Pfaff Subject: Re: [PATCH net-next-2.6] net: pskb_expand_head() optimization Date: Sun, 12 Sep 2010 12:55:54 -0700 Message-ID: <87zkvmvir9.fsf@benpfaff.org> References: <20100911123140.GA1939@del.dom.local> <20100911.203002.193707453.davem@davemloft.net> <20100912104534.GA2056@del.dom.local> <20100912.085833.226777368.davem@davemloft.net> Reply-To: Ben Pfaff Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: jarkao2@gmail.com, eric.dumazet@gmail.com, netdev@vger.kernel.org To: David Miller Return-path: Received: from outmail149080.authsmtp.com ([62.13.149.80]:51044 "EHLO outmail149080.authsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753654Ab0ILU1w (ORCPT ); Sun, 12 Sep 2010 16:27:52 -0400 In-Reply-To: <20100912.085833.226777368.davem@davemloft.net> (David Miller's message of "Sun, 12 Sep 2010 08:58:33 -0700 (PDT)") Sender: netdev-owner@vger.kernel.org List-ID: David Miller writes: >> 3) since skb_clone has some cost too, why e.g. saving only the pointer >> to the tail of the list in skb_shared_info isn't enough? > > Then we won't get the rest of the advantages of using list_head such > as prefetching during traversals, automatic debugging facilities, et al. Did you see the recent patch from Andi Kleen where he proposes removing this prefetching in most situations because the costs outweigh the benefits on most modern architectures? http://permalink.gmane.org/gmane.linux.kernel/1033281 I'm not saying that list_head doesn't have other advantages though. -- Ben Pfaff http://benpfaff.org