From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id EBBC16B022F for ; Sat, 24 Apr 2010 14:27:52 -0400 (EDT) Message-ID: <4BD33822.2000604@redhat.com> Date: Sat, 24 Apr 2010 21:27:46 +0300 From: Avi Kivity MIME-Version: 1.0 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: owner-linux-mm@kvack.org 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 List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org