Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752859Ab0DXS2F (ORCPT ); Sat, 24 Apr 2010 14:28:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60723 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751179Ab0DXS2C (ORCPT ); Sat, 24 Apr 2010 14:28:02 -0400 Message-ID: <4BD33822.2000604@redhat.com> Date: Sat, 24 Apr 2010 21:27:46 +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: ngupta@vflare.org CC: Dan Magenheimer , linux-kernel@vger.kernel.org, linux-mm@kvack.org, jeremy@goop.org, hugh.dickins@tiscali.co.uk, 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> <4830bd20-77b7-46c8-994b-8b4fa9a79d27@default> <4BD1B427.9010905@redhat.com> <4BD24E37.30204@vflare.org> In-Reply-To: <4BD24E37.30204@vflare.org> 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: 1395 Lines: 34 On 04/24/2010 04:49 AM, Nitin Gupta wrote: > >> I see. So why not implement this as an ordinary swap device, with a >> higher priority than the disk device? this way we reuse an API and keep >> things asynchronous, instead of introducing a special purpose API. >> >> > ramzswap is exactly this: an ordinary swap device which stores every page > in (compressed) memory and its enabled as highest priority swap. Currently, > it stores these compressed chunks in guest memory itself but it is not very > difficult to send these chunks out to host/hypervisor using virtio. > > However, it suffers from unnecessary block I/O layer overhead and requires > weird hooks in swap code, say to get notification when a swap slot is freed. > Isn't that TRIM? > OTOH frontswap approach gets rid of any such artifacts and overheads. > (ramzswap: http://code.google.com/p/compcache/) > Maybe we should optimize these overheads instead. Swap used to always be to slow devices, but swap-to-flash has the potential to make swap act like an extension of RAM. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- 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/