From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx133.postini.com [74.125.245.133]) by kanga.kvack.org (Postfix) with SMTP id 177DF6B0032 for ; Wed, 15 May 2013 16:56:11 -0400 (EDT) MIME-Version: 1.0 Message-ID: <25f0f975-d9aa-4e00-bc34-acfd9b86b6bd@default> Date: Wed, 15 May 2013 13:55:44 -0700 (PDT) From: Dan Magenheimer Subject: RE: [PATCHv11 3/4] zswap: add to mm/ References: <1368448803-2089-1-git-send-email-sjenning@linux.vnet.ibm.com> <1368448803-2089-4-git-send-email-sjenning@linux.vnet.ibm.com> <15c5b1da-132a-4c9e-9f24-bc272d3865d5@default> <20130514163541.GC4024@medulla> <20130514225501.GA11956@cerebellum> <4d74f5db-11c1-4f58-97f4-8d96bbe601ac@default> <20130515185506.GA23342@phenom.dumpdata.com> <20130515200942.GA17724@cerebellum> <5193EEE7.80603@sr71.net> In-Reply-To: <5193EEE7.80603@sr71.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen , Seth Jennings Cc: Konrad Wilk , Andrew Morton , Greg Kroah-Hartman , Nitin Gupta , Minchan Kim , Robert Jennings , Jenifer Hopper , Mel Gorman , Johannes Weiner , Rik van Riel , Larry Woodman , Benjamin Herrenschmidt , Joe Perches , Joonsoo Kim , Cody P Schafer , Hugh Dickens , Paul Mackerras , linux-mm@kvack.org, linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org > From: Dave Hansen [mailto:dave@sr71.net] > Sent: Wednesday, May 15, 2013 2:24 PM > To: Seth Jennings > Cc: Konrad Rzeszutek Wilk; Dan Magenheimer; Andrew Morton; Greg Kroah-Har= tman; Nitin Gupta; Minchan > Kim; Robert Jennings; Jenifer Hopper; Mel Gorman; Johannes Weiner; Rik va= n Riel; Larry Woodman; > Benjamin Herrenschmidt; Joe Perches; Joonsoo Kim; Cody P Schafer; Hugh Di= ckens; Paul Mackerras; linux- > mm@kvack.org; linux-kernel@vger.kernel.org; devel@driverdev.osuosl.org > Subject: Re: [PATCHv11 3/4] zswap: add to mm/ >=20 > On 05/15/2013 01:09 PM, Seth Jennings wrote: > > On Wed, May 15, 2013 at 02:55:06PM -0400, Konrad Rzeszutek Wilk wrote: > >>> Sorry, but I don't think that's appropriate for a patch in the MM sub= system. > >> > >> Perhaps a compromise can be reached where this code is merged as a dri= ver > >> not a core mm component. There is a high bar to be in the MM - it has = to > >> work with many many different configurations. > >> > >> And drivers don't have such a high bar. They just need to work on a sp= ecific > >> issue and that is it. If zswap ended up in say, drivers/mm that would = make > >> it more palpable I think. >=20 > The issue is not whether it is a loadable module or a driver. Nobody > here is stupid enough to say, "hey, now it's a driver/module, all of the > complex VM interactions are finally fixed!" >=20 > If folks don't want this in their system, there's a way to turn it off, > today, with the sysfs tunables. We don't need _another_ way to turn it > off at runtime (unloading the module/driver). The issue is we KNOW the complex VM interactions are NOT fixed and there has been very very little breadth testing (i.e. across a wide range of workloads, and any attempts to show how much harm can come from enabling it.) That's (at least borderline) acceptable in a driver that can be unloaded, but not in MM code IMHO. -- 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