Received: with ECARTIS (v1.0.0; list netdev); Fri, 13 Jun 2003 18:38:44 -0700 (PDT) Received: from pizda.ninka.net (IDENT:root@pizda.ninka.net [216.101.162.242]) by oss.sgi.com (8.12.9/8.12.9) with SMTP id h5E1cY2x029131 for ; Fri, 13 Jun 2003 18:38:34 -0700 Received: from localhost (IDENT:davem@localhost.localdomain [127.0.0.1]) by pizda.ninka.net (8.9.3/8.9.3) with ESMTP id SAA03622; Fri, 13 Jun 2003 18:34:40 -0700 Date: Fri, 13 Jun 2003 18:34:40 -0700 (PDT) Message-Id: <20030613.183440.41634090.davem@redhat.com> To: anton@samba.org Cc: scott.feldman@intel.com, haveblue@us.ibm.com, hdierks@us.ibm.com, dwg@au1.ibm.com, linux-kernel@vger.kernel.org, milliner@us.ibm.com, ricardoz@us.ibm.com, twichell@us.ibm.com, netdev@oss.sgi.com Subject: Re: e1000 performance hack for ppc64 (Power4) From: "David S. Miller" In-Reply-To: <20030614005534.GF32097@krispykreme> References: <20030613.165250.41635765.davem@redhat.com> <20030614005534.GF32097@krispykreme> X-FalunGong: Information control. X-Mailer: Mew version 2.1 on Emacs 21.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-archive-position: 3226 X-ecartis-version: Ecartis v1.0.0 Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com X-original-sender: davem@redhat.com Precedence: bulk X-list: netdev From: Anton Blanchard Date: Sat, 14 Jun 2003 10:55:34 +1000 What I think is happening is that we arent tripping the prefetch logic. We should take a latency hit for only the first cacheline at which point the host bridge decides to start prefetching for us. If not then we take take the latency hit on each transaction. It sounds like what happens is that the sub-cacheline word reads don't trigger the prefetch, but the first PCI read multiple transaction does.