From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937018AbXG0LsT (ORCPT ); Fri, 27 Jul 2007 07:48:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753958AbXG0LsL (ORCPT ); Fri, 27 Jul 2007 07:48:11 -0400 Received: from mail.gmx.net ([213.165.64.20]:34216 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1756259AbXG0LsK (ORCPT ); Fri, 27 Jul 2007 07:48:10 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX19ia6NDArdiA/Af3hKaFhPDGkHkL3IlFqCmvgHTnt RyJEwM2gXjstjl Subject: Re: updatedb From: Mike Galbraith To: Rene Herman Cc: Jesper Juhl , Andika Triwidada , Robert Deaton , linux-kernel@vger.kernel.org, ck list , linux-mm@kvack.org, B.Steinbrink@gmx.de, Andrew Morton In-Reply-To: <46A9D26E.9010703@gmail.com> References: <367a23780707250830i20a04a60n690e8da5630d39a9@mail.gmail.com> <46A773EA.5030103@gmail.com> <46A81C39.4050009@gmail.com> <7e0bae390707252323k2552c701x5673c55ff2cf119e@mail.gmail.com> <9a8748490707261746p638e4a98p3cdb7d9912af068a@mail.gmail.com> <46A98A14.3040300@gmail.com> <1185522844.6295.64.camel@Homer.simpson.net> <46A9ACB2.9030302@gmail.com> <1185528368.7851.44.camel@Homer.simpson.net> <46A9D26E.9010703@gmail.com> Content-Type: text/plain Date: Fri, 27 Jul 2007 13:48:00 +0200 Message-Id: <1185536880.8978.34.camel@Homer.simpson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.8.2 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2007-07-27 at 13:09 +0200, Rene Herman wrote: > On 07/27/2007 11:26 AM, Mike Galbraith wrote: > > > Updatedb finishes, freeing some ram (doesn't matter how much) > > Will be very little and swap-prefetch at least in its current form needs > more than very little to start doing anything: > > http://ck.kolivas.org/patches/swap-prefetch/2.6.21-swap_prefetch-38.patch > > | /* > | * Set max number of entries to 2/3 the size of physical ram as we > | * only ever prefetch to consume 2/3 of the ram. > | */ > > However, okay, let's just ignore that and pretend it kicks in even with the > little free memory updatedb itself left behind when it finished: Hm. I didn't read the patch, so I'm only going on what you quoted. >>From that, all I see is a limit on how much will be used total, and 2/3 of physical ram is a bunch. This quote doesn't say free ram, it says physical ram. If it really does use only free ram, that indeed sounds pretty pointless. I believe the users who say their apps really do get paged back in though, so suspect that's not the case. Anyway, I only offered a simple explanation of how swap-prefetching can indeed help (and possibly hurt) with something like updatedb, not an analysis of it's current implementation ;-) I'd have to read it, and test it myself to do that, but my world doesn't have a need for it, so... -Mike