From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH 0/2] Get rid of ndo_xmit_flush Date: Wed, 27 Aug 2014 13:45:10 -0700 (PDT) Message-ID: <20140827.134510.2172564669938048576.davem@davemloft.net> References: <20140825.163458.1117073971092495452.davem@davemloft.net> <1409142672.26515.24.camel@localhost> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, therbert@google.com, jhs@mojatatu.com, edumazet@google.com, jeffrey.t.kirsher@intel.com, rusty@rustcorp.com.au, dborkman@redhat.com, brouer@redhat.com To: hannes@stressinduktion.org Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:40207 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964892AbaH0UpM (ORCPT ); Wed, 27 Aug 2014 16:45:12 -0400 In-Reply-To: <1409142672.26515.24.camel@localhost> Sender: netdev-owner@vger.kernel.org List-ID: From: Hannes Frederic Sowa Date: Wed, 27 Aug 2014 14:31:12 +0200 > On Mo, 2014-08-25 at 16:34 -0700, David Miller wrote: >> Given Jesper's performance numbers, it's not the way to go. >> >> Instead, go with a signalling scheme via new boolean skb->xmit_more. >> >> This has several advantages: >> >> 1) Nearly trivial driver support, just protect the tail pointer >> update with the skb->xmit_more check. > > One thing one should keep in mind is, that there must be a skb available > to trigger the flush, maybe this will hurt us one day. > > Thinking more about it should we go with a coccinelle script and > replace/extend ndo_start_xmit with an additional argument? > > We can also add a new function pointer and call that instead of > ndo_start_xmit. I think only the callq *%rax hurts performance. I don't think we will have any problems here, the caller will always be the entity which analyzes the upcoming set of SKBs to submit and tag them properly. I really do not want to add a new OP and I even more so do not want to adjust the ndo_start_xmit() signature. It's effect is far reaching, and for absolutely no gain as far as I can see. Thanks.