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 675546B01B7 for ; Mon, 14 Jun 2010 04:09:47 -0400 (EDT) Message-ID: <4C15E3C8.20407@redhat.com> Date: Mon, 14 Jun 2010 11:09:44 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [RFC/T/D][PATCH 2/2] Linux/Guest cooperative unmapped page cache control References: <20100608155140.3749.74418.sendpatchset@L34Z31A.ibm.com> <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> In-Reply-To: <20100611045600.GE5191@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 06/11/2010 07:56 AM, Balbir Singh wrote: > >> Just to be clear, let's say we have a mapped page (say of /sbin/init) >> that's been unreferenced since _just_ after the system booted. We also >> have an unmapped page cache page of a file often used at runtime, say >> one from /etc/resolv.conf or /etc/passwd. >> >> Which page will be preferred for eviction with this patch set? >> >> > In this case the order is as follows > > 1. First we pick free pages if any > 2. If we don't have free pages, we go after unmapped page cache and > slab cache > 3. If that fails as well, we go after regularly memory > > In the scenario that you describe, we'll not be able to easily free up > the frequently referenced page from /etc/*. The code will move on to > step 3 and do its regular reclaim. > Still it seems to me you are subverting the normal order of reclaim. I don't see why an unmapped page cache or slab cache item should be evicted before a mapped page. Certainly the cost of rebuilding a dentry compared to the gain from evicting it, is much higher than that of reestablishing a mapped page. -- 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