From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id D8ABB60021B for ; Mon, 28 Dec 2009 10:58:09 -0500 (EST) MIME-Version: 1.0 Message-ID: Date: Mon, 28 Dec 2009 07:57:28 -0800 (PST) From: Dan Magenheimer Subject: RE: Tmem [PATCH 0/5] (Take 3): Transcendent memory In-Reply-To: <20091225191848.GB8438@elf.ucw.cz> Content-Type: text/plain; charset=Windows-1252 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: Pavel Machek Cc: Nitin Gupta , Nick Piggin , Andrew Morton , jeremy@goop.org, xen-devel@lists.xensource.com, tmem-devel@oss.oracle.com, Rusty Russell , Rik van Riel , dave.mccracken@oracle.com, sunil.mushran@oracle.com, Avi Kivity , Schwidefsky , Balbir Singh , Marcelo Tosatti , Alan Cox , chris.mason@oracle.com, linux-mm , linux-kernel List-ID: > From: Pavel Machek [mailto:pavel@ucw.cz] > > > As I mentioned, I really like the idea behind tmem. All I=20 > am proposing > > > is that we should probably explore some alternatives to=20 > achive this using > > > some existing infrastructure in kernel. > >=20 > > Hi Nitin -- > >=20 > > Sorry if I sounded overly negative... too busy around the holidays. > >=20 > > I'm definitely OK with exploring alternatives. I just think that > > existing kernel mechanisms are very firmly rooted in the notion > > that either the kernel owns the memory/cache or an asynchronous > > device owns it. Tmem falls somewhere in between and is very >=20 > Well... compcache seems to be very similar to preswap: in preswap case > you don't know if hypervisor will have space, in ramzswap you don't > know if data are compressible. Hi Pavel -- Yes there are definitely similarities too. In fact, I started prototyping preswap (now called frontswap) with Nitin's compcache code. IIRC I ran into some problems with compcache's difficulties in dealing with failed "puts" due to dynamic changes in size of hypervisor-available-memory. Nitin may have addressed this in later versions of ramzswap. One feature of frontswap which is different than ramzswap is that frontswap acts as a "fronting store" for all configured swap devices, including SAN/NAS swap devices. It doesn't need to be separately configured as a "highest priority" swap device. In many installations and depending on how ramzswap is configured, this difference probably doesn't make much difference though. Thanks, Dan -- 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