Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261890AbVCLJKv (ORCPT ); Sat, 12 Mar 2005 04:10:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261888AbVCLJKv (ORCPT ); Sat, 12 Mar 2005 04:10:51 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:31717 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S261890AbVCLJKp (ORCPT ); Sat, 12 Mar 2005 04:10:45 -0500 Subject: Re: [PATCH] Prefaulting From: Arjan van de Ven To: Andrew Morton Cc: Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@vger.kernel.org, torvalds@osdl.org In-Reply-To: <20050311172228.773cf03d.akpm@osdl.org> References: <20050311172228.773cf03d.akpm@osdl.org> Content-Type: text/plain Date: Sat, 12 Mar 2005 10:10:36 +0100 Message-Id: <1110618637.6292.36.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-3) Content-Transfer-Encoding: 7bit X-Spam-Score: 4.1 (++++) X-Spam-Report: SpamAssassin version 2.63 on pentafluge.infradead.org summary: Content analysis details: (4.1 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.3 RCVD_NUMERIC_HELO Received: contains a numeric HELO 1.1 RCVD_IN_DSBL RBL: Received via a relay in list.dsbl.org [] 2.5 RCVD_IN_DYNABLOCK RBL: Sent directly from dynamic IP address [80.57.133.107 listed in dnsbl.sorbs.net] 0.1 RCVD_IN_SORBS RBL: SORBS: sender is listed in SORBS [80.57.133.107 listed in dnsbl.sorbs.net] X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1063 Lines: 22 > >From a quick peek it seems that the patch makes negligible difference for a > kernel compilation when prefaulting 1-2 pages and slows the workload down > quite a lot when prefaulting up to 16 pages. well the last time I saw prefaulting experiments (Ingo was involved iirc) the problem was that the hitrate for the prefaults was such that the costs for tearing down the extra redundant rmap chains was more expensive than taking the "extra" faults. It seems linux has pretty cheap faulting logic invalidating some of traditional OS assumptions... (fwiw one of the worst tests I remember was doing a lot of very short shell script executions; the case where bash lives briefly so that you get maximum cost for the extra teardowns while not a lot of bash gets run so prefaulting doesn't make a lot of difference) - 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/