From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx135.postini.com [74.125.245.135]) by kanga.kvack.org (Postfix) with SMTP id 405726B0034 for ; Wed, 29 May 2013 15:53:28 -0400 (EDT) Received: from /spool/local by e36.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 29 May 2013 13:53:27 -0600 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 034A319D8045 for ; Wed, 29 May 2013 13:50:28 -0600 (MDT) Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r4TJoZUF154896 for ; Wed, 29 May 2013 13:50:35 -0600 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r4TJoXLM024080 for ; Wed, 29 May 2013 13:50:34 -0600 Date: Wed, 29 May 2013 14:50:27 -0500 From: Seth Jennings Subject: Re: [PATCHv12 3/4] zswap: add to mm/ Message-ID: <20130529195027.GC428@cerebellum> References: <1369067168-12291-1-git-send-email-sjenning@linux.vnet.ibm.com> <1369067168-12291-4-git-send-email-sjenning@linux.vnet.ibm.com> <20130528145918.acbd84df00313e527cf04d1b@linux-foundation.org> <20130529145720.GA428@cerebellum> <20130529112929.24005ae9cf1d9d636b2ea42f@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130529112929.24005ae9cf1d9d636b2ea42f@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Greg Kroah-Hartman , Nitin Gupta , Minchan Kim , Konrad Rzeszutek Wilk , Dan Magenheimer , Robert Jennings , Jenifer Hopper , Mel Gorman , Johannes Weiner , Rik van Riel , Larry Woodman , Benjamin Herrenschmidt , Dave Hansen , Joe Perches , Joonsoo Kim , Cody P Schafer , Hugh Dickens , Paul Mackerras , Heesub Shin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org On Wed, May 29, 2013 at 11:29:29AM -0700, Andrew Morton wrote: > On Wed, 29 May 2013 09:57:20 -0500 Seth Jennings wrote: > > > > > +/********************************* > > > > +* helpers > > > > +**********************************/ > > > > +static inline bool zswap_is_full(void) > > > > +{ > > > > + return (totalram_pages * zswap_max_pool_percent / 100 < > > > > + zswap_pool_pages); > > > > +} > > > > > > We have had issues in the past where percentage-based tunables were too > > > coarse on very large machines. For example, a terabyte machine where 0 > > > bytes is too small and 10GB is too large. > > > > Yes, this is known limitation of the code right now and it is a high priority > > to come up with something better. It isn't clear what dynamic sizing policy > > should be used so, until such time as that policy can be determined, this is a > > simple stop-gap that works well enough for simple setups. > > It's a module parameter and hence is part of the userspace interface. > It's undesirable that the interface be changed, and it would be rather > dumb to merge it as-is when we *know* that it will be changed. > > I don't think we can remove the parameter altogether (or can we?), so I > suggest we finalise it ASAP. Perhaps rename it to > zswap_max_pool_ratio, with a range 1..999999. Better ideas needed :( zswap_max_pool_ratio is fine with me. I'm not entirely clear on the change though. Would that just be a name change or a change in meaning? Also, we can keep the tunable as I imagine there will always be some use for a manual override of the (future) dynamic policy. When the dynamic policy is available, we can just say that zswap_max_pool_ratio = 0 means "use dynamic policy" and change the default to 0. Does that sounds reasonable? Seth -- 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