From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: [PATCH] mlx4_en: map entire pages to increase throughput Date: Tue, 17 Jul 2012 11:17:46 -0700 Message-ID: <5005AC4A.9030208@hp.com> References: <1342458113-10384-1-git-send-email-cascardo@linux.vnet.ibm.com> <50044F1D.6000703@hp.com> <20120716.222903.367603216293954363.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "cascardo@linux.vnet.ibm.com" , "netdev@vger.kernel.org" , "yevgenyp@mellanox.co.il" , "ogerlitz@mellanox.com" , "amirv@mellanox.com" , "brking@linux.vnet.ibm.com" , "leitao@linux.vnet.ibm.com" , "klebers@linux.vnet.ibm.com" To: David Miller Return-path: Received: from g5t0007.atlanta.hp.com ([15.192.0.44]:23912 "EHLO g5t0007.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756322Ab2GQSRu (ORCPT ); Tue, 17 Jul 2012 14:17:50 -0400 In-Reply-To: <20120716.222903.367603216293954363.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On 07/16/2012 10:29 PM, David Miller wrote: > From: Rick Jones > Date: Mon, 16 Jul 2012 10:27:57 -0700 > >> That seems rather extraordinarily low - Power7 is supposed to be a >> rather high performance CPU. The last time I noticed O(3Gbit/s) on >> 10G for bulk transfer was before the advent of LRO/GRO - that was in >> the x86 space though. Is mapping really that expensive with Power7? > > Unfortunately, IOMMU mappings are incredibly expensive. I see effects > like this on Sparc too. OK, so that has caused some dimm memory to get a small refresh - it ends up being akin to if not actually a PIO yes? I recall schemes in drivers in other stacks whereby "small" packets were copied because it was cheaper to allocate/copy then it was to remap. rick jones