From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx160.postini.com [74.125.245.160]) by kanga.kvack.org (Postfix) with SMTP id DB68D6B004A for ; Thu, 26 Apr 2012 12:09:07 -0400 (EDT) Date: Thu, 26 Apr 2012 17:08:52 +0100 From: Richard Davies Subject: Re: [RFC][PATCH] avoid swapping out with swappiness==0 Message-ID: <20120426160852.GA12568@alpha.arachsys.com> References: <20120424082019.GA18395@alpha.arachsys.com> <4F996BA6.9010900@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F996BA6.9010900@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: Christoph Lameter , Satoru Moriya , Jerome Marchand , KOSAKI Motohiro , "jweiner@redhat.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "riel@redhat.com" , "lwoodman@redhat.com" , "shaohua.li@intel.com" , "dle-develop@lists.sourceforge.net" , Seiji Aguchi , Minchan Kim KOSAKI Motohiro wrote: > Christoph Lameter wrote: > > Richard Davies wrote: > > > > > I strongly believe that Linux should have a way to turn off swapping unless > > > absolutely necessary. This means that users like us can run with swap > > > present for emergency use, rather than having to disable it because of the > > > side effects. > > > > Agree. And this ooperation mode should be the default behavior given that > > swapping is a very slow and tedious process these days. > > Even though current patch is not optimal, I don't disagree this opinion. Can > you please explain your use case? Why don't you use swapoff? My use case is that I have large (64 or 128GB RAM) qemu-kvm virtualization hosts, running many (20-50) VMs. Typically the total memory in use is less than physical memory. In these cases I would like the virtualization host to run without any swapping. I have set swappiness==0, but in practise I get big load spikes from swapping. See http://marc.info/?l=linux-mm&m=133517452117581 I don't want to run swapoff, because sometimes I will need to provision slightly more VMs than physical memory, and in these cases I would rather that the system runs with a little swap in use rather than the OOM killer occurring. Richard. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org