From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763602AbXKNGMy (ORCPT ); Wed, 14 Nov 2007 01:12:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758432AbXKNGMo (ORCPT ); Wed, 14 Nov 2007 01:12:44 -0500 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:41189 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1757489AbXKNGMn (ORCPT ); Wed, 14 Nov 2007 01:12:43 -0500 Date: Tue, 13 Nov 2007 22:12:42 -0800 (PST) Message-Id: <20071113.221242.153352652.davem@davemloft.net> To: nickpiggin@yahoo.com.au Cc: clameter@sgi.com, netdev@vger.kernel.org, herbert@gondor.apana.org.au, linux-kernel@vger.kernel.org Subject: Re: 2.6.24-rc2: Network commit causes SLUB performance regression with tbench From: David Miller In-Reply-To: <200711140436.24492.nickpiggin@yahoo.com.au> References: <200711132241.59074.nickpiggin@yahoo.com.au> <20071113.175804.151698768.davem@davemloft.net> <200711140436.24492.nickpiggin@yahoo.com.au> X-Mailer: Mew version 5.2 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Nick Piggin Date: Wed, 14 Nov 2007 04:36:24 +1100 > On Wednesday 14 November 2007 12:58, David Miller wrote: > > I suspect the issue is about having a huge skb->data linear area for > > TCP sends over loopback. We're likely getting a much smaller > > skb->data linear data area after the patch in question, the rest using > > the sk_buff scatterlist pages which are a little bit more expensive to > > process. > > It didn't seem to be noticeable at 1 client. Unless scatterlist > processing is going to cause cacheline bouncing, I don't see why this > hurts more as you add CPUs? Is your test system using HIGHMEM? That's one thing the page vector in the sk_buff can do a lot, kmaps.