From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx205.postini.com [74.125.245.205]) by kanga.kvack.org (Postfix) with SMTP id 493328D0001 for ; Fri, 11 May 2012 10:10:21 -0400 (EDT) Received: by pbbrp2 with SMTP id rp2so4625115pbb.14 for ; Fri, 11 May 2012 07:10:20 -0700 (PDT) Date: Fri, 11 May 2012 07:10:01 -0700 (PDT) From: Hugh Dickins Subject: Re: [PATCH] mm: raise MemFree by reverting percpu_pagelist_fraction to 0 In-Reply-To: <4FACD00D.4060003@kernel.org> Message-ID: References: <4FACD00D.4060003@kernel.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Sasha Levin , Linus Torvalds , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Fri, 11 May 2012, Minchan Kim wrote: > On 05/11/2012 05:30 PM, Sasha Levin wrote: > > >> Commit 93278814d359 "mm: fix division by 0 in percpu_pagelist_fraction()" > >> mistakenly initialized percpu_pagelist_fraction to the sysctl's minimum 8, > >> which leaves 1/8th of memory on percpu lists (on each cpu??); but most of > >> us expect it to be left unset at 0 (and it's not then used as a divisor). > > > > I'm a bit confused about this, does it mean that once you set > > percpu_pagelist_fraction to a value above the minimum, you can no > > longer set it back to being 0? > > > Unfortunately, Yes. :( > It's rather awkward and need fix. It's inelegant, but does that actually need a fix? Has anybody asked for that option in the six years of percpu_pagelist_fraction? Does setting percpu_pagelist_fraction to some large number perhaps approximate to the default behaviour of percpu_pagelist_fraction 0? I don't care very much either way - just don't want this discussion to divert from applying last night's fix to the default behaviour that most people expect. Hugh -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org