Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161498Ab2JXWfu (ORCPT ); Wed, 24 Oct 2012 18:35:50 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:35628 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161270Ab2JXWft (ORCPT ); Wed, 24 Oct 2012 18:35:49 -0400 Message-ID: <50886D3F.9050403@jp.fujitsu.com> Date: Wed, 24 Oct 2012 18:35:43 -0400 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:16.0) Gecko/20121010 Thunderbird/16.0.1 MIME-Version: 1.0 To: akpm@linux-foundation.org CC: bp@alien8.de, dave@linux.vnet.ibm.com, mhocko@suse.cz, linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, kosaki.motohiro@jp.fujitsu.com, linux-kernel@vger.kernel.org, rjw@sisk.pl Subject: Re: [PATCH] add some drop_caches documentation and info messsge References: <20121012125708.GJ10110@dhcp22.suse.cz> <20121023164546.747e90f6.akpm@linux-foundation.org> <20121024062938.GA6119@dhcp22.suse.cz> <20121024125439.c17a510e.akpm@linux-foundation.org> <50884F63.8030606@linux.vnet.ibm.com> <20121024134836.a28d223a.akpm@linux-foundation.org> <20121024210600.GA17037@liondog.tnic> <20121024141303.0797d6a1.akpm@linux-foundation.org> In-Reply-To: <20121024141303.0797d6a1.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1293 Lines: 39 >> 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. shrink_all_memory() drop minimum memory to be needed from hibernation. that's trade off matter. - drop all page cache pros. speed up hibernation time cons. after go back from hibernation, system works very slow a while until system will get enough file cache. - drop minimum page cache pros. system works quickly when go back from hibernation. cons. relative large hibernation time So, I'm not fun change hibernation default. hmmm... Does adding tracepint instead of printk makes sense? -- 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/