Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752924Ab0APM6p (ORCPT ); Sat, 16 Jan 2010 07:58:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752167Ab0APM6p (ORCPT ); Sat, 16 Jan 2010 07:58:45 -0500 Received: from astoria.ccjclearline.com ([64.235.106.9]:45103 "EHLO astoria.ccjclearline.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752099Ab0APM6o (ORCPT ); Sat, 16 Jan 2010 07:58:44 -0500 Date: Sat, 16 Jan 2010 07:57:40 -0500 (EST) From: "Robert P. J. Day" X-X-Sender: rpjday@localhost To: Sitsofe Wheeler cc: "H. Peter Anvin" , Yuhong Bao , Linus Torvalds , mingo@redhat.com, linux-kernel@vger.kernel.org Subject: Re: Ubuntu 32-bit, 32-bit PAE, 64-bit Kernel Benchmarks In-Reply-To: <20100116123313.GA20059@sucs.org> Message-ID: References: <4B511B12.6010208@zytor.com> <20100116123313.GA20059@sucs.org> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - astoria.ccjclearline.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - crashcourse.ca X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 16 Jan 2010, Sitsofe Wheeler wrote: > On Fri, Jan 15, 2010 at 05:49:06PM -0800, H. Peter Anvin wrote: > > On 12/30/2009 05:29 PM, Yuhong Bao wrote: > > > > > > Given that Linus was once talking about the performance penalties of > > > PAE and HIGHMEM64G, perhaps you'd find these benchmarks done by > > > Phoronix of interest: > > > http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae > > > > > > > The big difference isn't between HIGHMEM4G (no PAE) and HIGHMEM64G > > (PAE), it's between HIGHMEM and !HIGHMEM. That cutoff is ~892 MB > > for a stock 32-bit kernel. > > Thanks for the clarification - I had been wondering about why those > settings had been benchmarked against each other... > > I took a mild interest because I have an EeePC 900 with 1G of RAM. > The machine can do PAE but my understanding is that this would lead > to a performance drop (I currently have VMSPLIT_3G so I can use all > 1G of memory) so I run it without HIGHMEM. actually, it's 896M, not 892M, and i believe it's defined in arch/x86/mm/init_32.c: #define high_memory (-128UL << 20) BUILD_BUG_ON(VMALLOC_START >= VMALLOC_END); #undef high_memory interesting that it's a hardcoded value -- is there reason that wasn't configurable? (he asked from a position of total ignorance.) rday -- ======================================================================== Robert P. J. Day Waterloo, Ontario, CANADA Linux Consulting, Training and Kernel Pedantry. Web page: http://crashcourse.ca Twitter: http://twitter.com/rpjday ======================================================================== -- 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/