Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755170AbZDFTXt (ORCPT ); Mon, 6 Apr 2009 15:23:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752594AbZDFTXk (ORCPT ); Mon, 6 Apr 2009 15:23:40 -0400 Received: from gw.goop.org ([64.81.55.164]:42365 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752206AbZDFTXj (ORCPT ); Mon, 6 Apr 2009 15:23:39 -0400 Message-ID: <49DA56B7.9020905@goop.org> Date: Mon, 06 Apr 2009 12:23:35 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Martin Schwidefsky CC: Rik van Riel , akpm@osdl.org, Nick Piggin , frankeh@watson.ibm.com, virtualization@lists.osdl.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, hugh@veritas.com, Xen-devel Subject: Re: [patch 0/6] Guest page hinting version 7. References: <20090327150905.819861420@de.ibm.com> <200903281705.29798.rusty@rustcorp.com.au> <20090329162336.7c0700e9@skybase> <200904022232.02185.nickpiggin@yahoo.com.au> <20090402175249.3c4a6d59@skybase> <49D50CB7.2050705@redhat.com> <49D518E9.1090001@goop.org> <49D51CA9.6090601@redhat.com> <49D5215D.6050503@goop.org> <20090403104913.29c62082@skybase> <49D6532C.6010804@goop.org> <20090406092111.3b432edd@skybase> In-Reply-To: <20090406092111.3b432edd@skybase> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1095 Lines: 26 Martin Schwidefsky wrote: > Why should the guest want to do preswapping? It is as expensive for > the host to swap a page and get it back as it is for the guest (= one > write + one read). Yes, perhaps for swapping, but in general it makes sense for the guest to write the pages to backing store to prevent host swapping. For swap pages there's no big benefit, but for file-backed pages its better for the guest to do it. > The only thing you can gain by > putting memory pressure on the guest is to free some of the memory that > is used by the kernel for dentries, inodes, etc. > Well, that's also significant. My point is that the guest has multiple ways in which it can relieve its own memory pressure in response to overall system memory pressure; its just that I happened to pick the example where its much of a muchness. J -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/