Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759362Ab0D3TQ6 (ORCPT ); Fri, 30 Apr 2010 15:16:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50812 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757998Ab0D3QzK (ORCPT ); Fri, 30 Apr 2010 12:55:10 -0400 Message-ID: <4BD9D5BE.4010000@redhat.com> Date: Thu, 29 Apr 2010 21:53:50 +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: Pavel Machek CC: Dan Magenheimer , 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: <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@default4BD43033.7090706@redhat.com> <20100428055538.GA1730@ucw.cz> In-Reply-To: <20100428055538.GA1730@ucw.cz> 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: 1442 Lines: 35 On 04/28/2010 08:55 AM, Pavel Machek wrote: > >> That's a reasonable analogy. Frontswap serves nicely as an >> emergency safety valve when a guest has given up (too) much of >> its memory via ballooning but unexpectedly has an urgent need >> that can't be serviced quickly enough by the balloon driver. >> > wtf? So lets fix the ballooning driver instead? > You can't have a negative balloon size. The two models are not equivalent. Balloon allows you to give up a page for which you have a struct page. Frontswap (and swap) allows you to gain a page for which you don't have a struct page, but you can't access it directly. The similarity is that in both cases the host may want the guest to give up a page, but cannot force it. > There's no reason it could not be as fast as frontswap, right? > Actually I'd expect it to be faster -- it can deal with big chunks. > There's no reason for swapping and ballooning to behave differently when swap backing storage is RAM (they probably do now since swap was tuned for disks, not flash, but that's a bug if it's true). -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- 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/