From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] mlx4_en: map entire pages to increase throughput Date: Tue, 17 Jul 2012 13:20:19 -0700 (PDT) Message-ID: <20120717.132019.1633094178309164749.davem@davemloft.net> References: <20120716.222903.367603216293954363.davem@davemloft.net> <5005AC4A.9030208@hp.com> <5005C6A0.50002@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: rick.jones2@hp.com, cascardo@linux.vnet.ibm.com, netdev@vger.kernel.org, yevgenyp@mellanox.co.il, ogerlitz@mellanox.com, amirv@mellanox.com, leitao@linux.vnet.ibm.com, klebers@linux.vnet.ibm.com To: brking@linux.vnet.ibm.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:54452 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755206Ab2GQUUW (ORCPT ); Tue, 17 Jul 2012 16:20:22 -0400 In-Reply-To: <5005C6A0.50002@linux.vnet.ibm.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Brian King Date: Tue, 17 Jul 2012 15:10:08 -0500 > On 07/17/2012 01:17 PM, Rick Jones wrote: >> 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. > > On Power it ends up being an hcall to the hypervisor This is true on sparc64 niagara systems as well.