From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: [PATCH 39 of 39] IB/ipath - use streaming copy in RDMA interrupt handler to reduce packet loss Date: Thu, 29 Jun 2006 17:44:05 -0700 Message-ID: <44A473D5.70809@hp.com> References: <1151624063.10886.34.camel@chalcedony.pathscale.com> <20060629.164623.59469884.davem@davemloft.net> <44A47042.8060203@hp.com> <20060629.173206.48800902.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: bos@pathscale.com, akpm@osdl.org, rdreier@cisco.com, mst@mellanox.co.il, openib-general@openib.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: Received: from palrel12.hp.com ([156.153.255.237]:43981 "EHLO palrel12.hp.com") by vger.kernel.org with ESMTP id S1751338AbWF3AoH (ORCPT ); Thu, 29 Jun 2006 20:44:07 -0400 To: David Miller In-Reply-To: <20060629.173206.48800902.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org David Miller wrote: > From: Rick Jones > Date: Thu, 29 Jun 2006 17:28:50 -0700 > > >>I thought that most PCI controllers (that is to say the things bridging >>PCI to the rest of the system) could do prefetching and/or that PCI-X >>(if not PCI, no idea about PCI-e) cards could issue multiple >>transactions anyway? > > > People doing deep CMT chips have found out that all of that > prefetching and store buffering is unnecessary when everything is so > tightly integrated. Then is prefetching in memcpy really that important to them (BTW besides Sun/Niagra who are doing "deep CMT"?) > All of the previous UltraSPARC boxes before Niagara had a > streaming cache sitting on the PCI controller. It basically > prefetched for reads and collected writes from PCI devices > into cacheline sized chunks. > > The PCI controller in the current Niagara systems has none of that > stuff. Relying on PCI-X devices to issue multiple requests then? rick jones