Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753451Ab0DYMGh (ORCPT ); Sun, 25 Apr 2010 08:06:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53455 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753266Ab0DYMGf (ORCPT ); Sun, 25 Apr 2010 08:06:35 -0400 Message-ID: <4BD43033.7090706@redhat.com> Date: Sun, 25 Apr 2010 15:06:11 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: Dan Magenheimer CC: 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 Subject: Re: Frontswap [PATCH 0/4] (was Transcendent Memory): overview References: <20100422134249.GA2963@ca-server1.us.oracle.com> <4BD06B31.9050306@redhat.com> <53c81c97-b30f-4081-91a1-7cef1879c6fa@default> <4BD07594.9080905@redhat.com> <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@default> In-Reply-To: <1c02a94a-a6aa-4cbb-a2e6-9d4647760e91@default> Content-Type: text/plain; charset=UTF-8; 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: 1684 Lines: 40 On 04/25/2010 03:41 AM, Dan Magenheimer wrote: >>> No, ANY put_page can fail, and this is a critical part of the API >>> that provides all of the flexibility for the hypervisor and all >>> the guests. (See previous reply.) >>> >> The guest isn't required to do any put_page()s. It can issue lots of >> them when memory is available, and keep them in the hypervisor forever. >> Failing new put_page()s isn't enough for a dynamic system, you need to >> be able to force the guest to give up some of its tmem. >> > Yes, indeed, this is true. That is why it is important for any > policy implemented behind frontswap to "bill" the guest if it > is attempting to keep frontswap pages in the hypervisor forever > and to prod the guest to reclaim them when it no longer needs > super-fast emergency swap space. The frontswap patch already includes > the kernel mechanism to enable this and the prodding can be implemented > by a guest daemon (of which there already exists an existence proof). > In this case you could use the same mechanism to stop new put_page()s? Seems frontswap is like a reverse balloon, where the balloon is in hypervisor space instead of the guest space. > (While devil's advocacy is always welcome, frontswap is NOT a > cool academic science project where these issues have not been > considered or tested.) > Good to know. -- error compiling committee.c: too many arguments to function -- 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/