From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 061F86B023C for ; Fri, 30 Apr 2010 12:04:47 -0400 (EDT) Received: from d03relay03.boulder.ibm.com (d03relay03.boulder.ibm.com [9.17.195.228]) by e36.co.us.ibm.com (8.14.3/8.13.1) with ESMTP id o3UG1ati024491 for ; Fri, 30 Apr 2010 10:01:36 -0600 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay03.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o3UG4UnO105196 for ; Fri, 30 Apr 2010 10:04:31 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id o3UG4TUK028474 for ; Fri, 30 Apr 2010 10:04:29 -0600 Subject: Re: Frontswap [PATCH 0/4] (was Transcendent Memory): overview From: Dave Hansen In-Reply-To: <4BDA8324.7090409@redhat.com> References: <4BD16D09.2030803@redhat.com> <4BD1A74A.2050003@redhat.com> <4830bd20-77b7-46c8-994b-8b4fa9a79d27@default> <4BD1B427.9010905@redhat.com> <4BD1B626.7020702@redhat.com> <5fa93086-b0d7-4603-bdeb-1d6bfca0cd08@default> <4BD3377E.6010303@redhat.com> <1c02a94a-a6aa-4cbb-a2e6-9d4647760e91@default4BD43033.7090706@redhat.com> <20100428055538.GA1730@ucw.cz> <1272591924.23895.807.camel@nimitz> <4BDA8324.7090409@redhat.com> Content-Type: text/plain Date: Fri, 30 Apr 2010 09:04:26 -0700 Message-Id: <1272643466.23895.2529.camel@nimitz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Avi Kivity Cc: Pavel Machek , Dan Magenheimer , linux-kernel@vger.kernel.org, linux-mm@kvack.org, jeremy@goop.org, hugh.dickins@tiscali.co.uk, ngupta@vflare.org, JBeulich@novell.com, chris.mason@oracle.com, kurt.hackel@oracle.com, dave.mccracken@oracle.com, npiggin@suse.de, akpm@linux-foundation.org, riel@redhat.com List-ID: On Fri, 2010-04-30 at 10:13 +0300, Avi Kivity wrote: > On 04/30/2010 04:45 AM, Dave Hansen wrote: > > > > A large portion of CMM2's gain came from the fact that you could take > > memory away from guests without _them_ doing any work. If the system is > > experiencing a load spike, you increase load even more by making the > > guests swap. If you can just take some of their memory away, you can > > smooth that spike out. CMM2 and frontswap do that. The guests > > explicitly give up page contents that the hypervisor does not have to > > first consult with the guest before discarding. > > > > Frontswap does not do this. Once a page has been frontswapped, the host > is committed to retaining it until the guest releases it. It's really > not very different from a synchronous swap device. > > I think cleancache allows the hypervisor to drop pages without the > guest's immediate knowledge, but I'm not sure. Gah. You're right. I'm reading the two threads and confusing the concepts. I'm a bit less mystified why the discussion is revolving around the swap device so much. :) -- Dave -- 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/ . Don't email: email@kvack.org