From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932201Ab2J2JAN (ORCPT ); Mon, 29 Oct 2012 05:00:13 -0400 Received: from cantor2.suse.de ([195.135.220.15]:47123 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758163Ab2J2JAI (ORCPT ); Mon, 29 Oct 2012 05:00:08 -0400 Date: Mon, 29 Oct 2012 09:59:59 +0100 (CET) From: Jiri Kosina X-X-Sender: jikos@twin.jikos.cz To: Andrew Morton Cc: "Rafael J. Wysocki" , Borislav Petkov , Dave Hansen , Michal Hocko , linux-mm@kvack.org, KAMEZAWA Hiroyuki , KOSAKI Motohiro , LKML Subject: Re: [PATCH] add some drop_caches documentation and info messsge In-Reply-To: <20121024181752.de011615.akpm@linux-foundation.org> Message-ID: References: <20121012125708.GJ10110@dhcp22.suse.cz> <20121024210600.GA17037@liondog.tnic> <20121024141303.0797d6a1.akpm@linux-foundation.org> <1787395.7AzIesGUbB@vostro.rjw.lan> <20121024181752.de011615.akpm@linux-foundation.org> User-Agent: Alpine 2.00 (LRH 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 24 Oct 2012, Andrew Morton wrote: > > > > I have drop_caches in my suspend-to-disk script so that the hibernation > > > > image is kept at minimum and suspend times are as small as possible. > > > > > > hm, that sounds smart. > > > > > > > Would that be a valid use-case? > > > > > > I'd say so, unless we change the kernel to do that internally. We do > > > have the hibernation-specific shrink_all_memory() in the vmscan code. > > > We didn't see fit to document _why_ that exists, but IIRC it's there to > > > create enough free memory for hibernation to be able to successfully > > > complete, but no more. > > > > That's correct. > > Well, my point was: how about the idea of reclaiming clean pagecache > (and inodes, dentries, etc) before hibernation so we read/write less > disk data? You might or might not want to do that. Dropping caches around suspend makes the hibernation process itself faster, but the realtime response of the applications afterwards is worse, as everything touched by user has to be paged in again. -- Jiri Kosina SUSE Labs