From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752175Ab0CSHYG (ORCPT ); Fri, 19 Mar 2010 03:24:06 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:54746 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751496Ab0CSHYC (ORCPT ); Fri, 19 Mar 2010 03:24:02 -0400 Subject: Re: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter From: Dave Hansen To: Avi Kivity Cc: Anthony Liguori , balbir@linux.vnet.ibm.com, KVM development list , Rik van Riel , KAMEZAWA Hiroyuki , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" In-Reply-To: <4B9F49F1.70202@redhat.com> References: <20100315072214.GA18054@balbir.in.ibm.com> <4B9DE635.8030208@redhat.com> <20100315080726.GB18054@balbir.in.ibm.com> <4B9DEF81.6020802@redhat.com> <20100315091720.GC18054@balbir.in.ibm.com> <4B9DFD9C.8030608@redhat.com> <4B9E810E.9010706@codemonkey.ws> <4B9F49F1.70202@redhat.com> Content-Type: text/plain Date: Fri, 19 Mar 2010 00:23:52 -0700 Message-Id: <1268983432.10438.5685.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2010-03-16 at 11:05 +0200, Avi Kivity wrote: > > Not really. In many cloud environments, there's a set of common > > images that are instantiated on each node. Usually this is because > > you're running a horizontally scalable application or because you're > > supporting an ephemeral storage model. > > But will these servers actually benefit from shared cache? So the > images are shared, they boot up, what then? > > - apache really won't like serving static files from the host pagecache > - dynamic content (java, cgi) will be mostly in anonymous memory, not > pagecache > - ditto for application servers > - what else are people doing? Think of an OpenVZ-style model where you're renting out a bunch of relatively tiny VMs and they're getting used pretty sporadically. They either have relatively little memory, or they've been ballooned down to a pretty small footprint. The more you shrink them down, the more similar they become. You'll end up having things like init, cron, apache, bash and libc start to dominate the memory footprint in the VM. That's *certainly* a case where this makes a lot of sense. -- Dave