From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [PATCH 1/4] net: skb_orphan on dev_hard_start_xmit Date: Thu, 4 Jun 2009 13:24:57 +0930 Message-ID: <200906041324.59118.rusty@rustcorp.com.au> References: <200905292344.56814.rusty@rustcorp.com.au> <200906012157.29465.rusty@rustcorp.com.au> <4A26E4FD.5010405@gmail.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, Divy Le Ray , Roland Dreier , Pavel Emelianov , Dan Williams , libertas-dev@lists.infradead.org To: Eric Dumazet Return-path: Received: from ozlabs.org ([203.10.76.45]:33028 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754517AbZFDDzI convert rfc822-to-8bit (ORCPT ); Wed, 3 Jun 2009 23:55:08 -0400 In-Reply-To: <4A26E4FD.5010405@gmail.com> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 4 Jun 2009 06:32:53 am Eric Dumazet wrote: > Rusty Russell a =E9crit : > > On Sat, 30 May 2009 12:41:00 am Eric Dumazet wrote: > >> For TCP, I agree your patch is a huge benefit, since its paced by = remote > >> ACKS and window control > > > > I doubt that. There'll be some cache friendliness, but I'm not sur= e > > it'll be measurable, let alone "huge". =2E.. > We can see sock_wfree() being number 2 on the profile, because it tou= ches > three cache lines per socket and transmited packet in TX completion > handler. Interesting, I take it back: got some "after" stats as well? > Also, taking a reference on socket for each xmit packet in flight is = very > expensive, since it slows down receiver in __udp4_lib_lookup(). Sever= al > cpus are fighting for sk->refcnt cache line. Now we have decent dynamic per-cpu, we can finally implement bigrefs. = More=20 obvious for device counts than sockets, but perhaps applicable here as = well? Rusty.