Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 14 Nov 2001 09:45:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 14 Nov 2001 09:45:36 -0500 Received: from quark.didntduck.org ([216.43.55.190]:56338 "EHLO quark.didntduck.org") by vger.kernel.org with ESMTP id ; Wed, 14 Nov 2001 09:45:24 -0500 Message-ID: <3BF2837B.4B63FBA5@didntduck.org> Date: Wed, 14 Nov 2001 09:45:15 -0500 From: Brian Gerst X-Mailer: Mozilla 4.76 [en] (WinNT; U) X-Accept-Language: en MIME-Version: 1.0 To: Willi =?iso-8859-1?Q?N=FC=DFer?= CC: lkml Subject: Re: Comparison of PAE and Non-PAE 2..4.14 (p8) in high load In-Reply-To: <3BF27557.30007@sap.com> Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Willi N??er wrote: > > Hi, > > after my first posting to lkml where we compared distributor > provided kernels vs. a plain 2.4.14-pre8 it was pointed > out that between PAE and non-PAE kernels some performance > differences might exist. > > We checked this last night and here are the first results. > Again, > a) the relevant quantity dialog steps per second is a > measure for the throughput our application servers runs. > b) our application server and the corresponding database > (SAP DB) run on 4 way Dell, 1 GB at boot time enabled. > > Results: > --------- > > 2.4.7 > 2.4.14p8 PAE 2.4.14p4 non- PAE > ------------------------------------------------------------- > 1.80 13.42 15.47 > 1.10 13.28 14.76 > 1.20 14.08 14.63 > 1.26 13.17 15.30 > 1.35 13.41 14.51 > > This means that we did see a performance decrease of about > 6 % compared to 2.4.14p8 nonPAE but still 2.4.14p8 is an order > of magnitude faster than 2.4.7 PAE mode increases the size of the page table entries to 64-bits, and the x86 doesn't do 64-bit operations very well. Plus it has three levels of tables to work with instead of two. It is the only way to support more than 4GB of memory so it's a tradeoff between high memory support and performance. If you have less memory, don't run a PAE kernel. -- Brian Gerst - 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/