Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751256AbWAJS6b (ORCPT ); Tue, 10 Jan 2006 13:58:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751187AbWAJS6a (ORCPT ); Tue, 10 Jan 2006 13:58:30 -0500 Received: from master.soleranetworks.com ([67.137.28.188]:37271 "EHLO master.soleranetworks.com") by vger.kernel.org with ESMTP id S1751189AbWAJS63 (ORCPT ); Tue, 10 Jan 2006 13:58:29 -0500 Message-ID: <43C3EB4A.6000606@wolfmountaingroup.com> Date: Tue, 10 Jan 2006 10:13:46 -0700 From: "Jeff V. Merkey" User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040510 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Lennart Sorensen Cc: Bernd Eckenfels , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Re: 2G memory split References: <43C3E142.1080206@wolfmountaingroup.com> <20060110185030.GB26581@csclub.uwaterloo.ca> In-Reply-To: <20060110185030.GB26581@csclub.uwaterloo.ca> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1671 Lines: 51 Lennart Sorensen wrote: >On Tue, Jan 10, 2006 at 09:30:58AM -0700, Jeff V. Merkey wrote: > > >>Bernd Eckenfels wrote: >> >>Here are the patches I use for the splitting. They work well. The >>methods employed in Red Hat ES are far better and I am surprised >>no one has simply integrated those patches into the kernel which are 4GB >>/ 4GB kernel/user. >> >> > >I was under the impression the 4G/4G split had some non negligable >performance penalties compared to the other options. > > It does, but from my testing, I/O performance and app performance seems negligible. I run the highest performing app/driver on Linux for disk and network I/O loading and ES3 and ES4 are just as performant with 4:4 as FC2, FC3, and FC4 with 3:1. I am now able to capture 4 x gigabit segments with 3:1 at sustained stream to disk rates of 497 MB/S and 1 x 10Gbe at 517 MB/S stream to disk. I see no appreciable performance differences 3:1 vs. 4:4. Modern Xeon processors have gotten a lot better dealing with TLB invalidation. I suppose applications that remap memory all over the place or that do tons of swapping would see some penalty, and I do see some performance degredation when user space apps start swapping, but it's difficult to quantify how much is related to disk I/O latency vs. TLB overhear. Most TLB flushes will cost you 150 clocks over time as the TLB reloads itself. Jeff >Len Sorensen > > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/