From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937755AbXG0UhJ (ORCPT ); Fri, 27 Jul 2007 16:37:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934055AbXG0Ug4 (ORCPT ); Fri, 27 Jul 2007 16:36:56 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:58863 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763020AbXG0Ugz (ORCPT ); Fri, 27 Jul 2007 16:36:55 -0400 Subject: Re: swap-prefetch: A smart way to make good use of idle resources (was: updatedb) From: Arjan van de Ven To: Al Boldi Cc: linux-kernel@vger.kernel.org In-Reply-To: <200707272243.02336.a1426z@gawab.com> References: <200707272243.02336.a1426z@gawab.com> Content-Type: text/plain Organization: Intel International BV Date: Fri, 27 Jul 2007 13:34:58 -0700 Message-Id: <1185568498.2711.5.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.10.3 (2.10.3-1.fc7) Content-Transfer-Encoding: 7bit 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 > IMHO, what everybody agrees on, is that swap-prefetch has a positive effect > in some cases, and nobody can prove an adverse effect (excluding power > consumption). The reason for this positive effect is also crystal clear: > It prefetches from swap on idle into free memory, ie: it doesn't force the fact that there is free memory is ... strange. IN principle, Linux keeps almost no memory free (except some emergency buffers) so that things you swap in prematurely will BY DEFINITION go at the expense of other things that could be there.... also, they take up seek time (5 to 10 msec), so if you were to read something else at the time you get additional latency. so the conclusion that it only can be better (if you don't care about power) is imo premature. Sure it still can be worth it, but it for sure is NOT an automatic thing.