From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 86C356B01D2 for ; Tue, 15 Jun 2010 03:12:48 -0400 (EDT) Message-ID: <4C1727EC.2020500@redhat.com> Date: Tue, 15 Jun 2010 10:12:44 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [RFC/T/D][PATCH 2/2] Linux/Guest cooperative unmapped page cache control References: <20100608155153.3749.31669.sendpatchset@L34Z31A.ibm.com> <4C10B3AF.7020908@redhat.com> <20100610142512.GB5191@balbir.in.ibm.com> <1276214852.6437.1427.camel@nimitz> <20100611045600.GE5191@balbir.in.ibm.com> <4C15E3C8.20407@redhat.com> <20100614084810.GT5191@balbir.in.ibm.com> <1276528376.6437.7176.camel@nimitz> <20100614165853.GW5191@balbir.in.ibm.com> <1276535371.6437.7417.camel@nimitz> <20100614171624.GY5191@balbir.in.ibm.com> In-Reply-To: <20100614171624.GY5191@balbir.in.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: balbir@linux.vnet.ibm.com Cc: Dave Hansen , kvm , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On 06/14/2010 08:16 PM, Balbir Singh wrote: > * Dave Hansen [2010-06-14 10:09:31]: > > >> On Mon, 2010-06-14 at 22:28 +0530, Balbir Singh wrote: >> >>> If you've got duplicate pages and you know >>> that they are duplicated and can be retrieved at a lower cost, why >>> wouldn't we go after them first? >>> >> I agree with this in theory. But, the guest lacks the information about >> what is truly duplicated and what the costs are for itself and/or the >> host to recreate it. "Unmapped page cache" may be the best proxy that >> we have at the moment for "easy to recreate", but I think it's still too >> poor a match to make these patches useful. >> >> > That is why the policy (in the next set) will come from the host. As > to whether the data is truly duplicated, my experiments show up to 60% > of the page cache is duplicated. Isn't that incredibly workload dependent? We can't expect the host admin to know whether duplication will occur or not. -- error compiling committee.c: too many arguments to function -- 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