From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d06nrmr1407.portsmouth.uk.ibm.com (d06nrmr1407.portsmouth.uk.ibm.com [9.149.38.185]) by mtagate4.uk.ibm.com (8.13.8/8.13.8) with ESMTP id m6UCG3s3237840 for ; Wed, 30 Jul 2008 12:16:03 GMT Received: from d06av03.portsmouth.uk.ibm.com (d06av03.portsmouth.uk.ibm.com [9.149.37.213]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v9.0) with ESMTP id m6UCG3RN4272242 for ; Wed, 30 Jul 2008 13:16:03 +0100 Received: from d06av03.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av03.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m6UCG2V7001748 for ; Wed, 30 Jul 2008 13:16:03 +0100 Subject: Re: memory hotplug: hot-remove fails on lowest chunk in ZONE_MOVABLE From: Gerald Schaefer In-Reply-To: <20080730110444.27DE.E1E9C6FF@jp.fujitsu.com> References: <20080723105318.81BC.E1E9C6FF@jp.fujitsu.com> <1217347653.4829.17.camel@localhost.localdomain> <20080730110444.27DE.E1E9C6FF@jp.fujitsu.com> Content-Type: text/plain Date: Wed, 30 Jul 2008 14:16:01 +0200 Message-Id: <1217420161.4545.10.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Yasunori Goto Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, KAMEZAWA Hiroyuki , Dave Hansen , Andy Whitcroft , Christoph Lameter , Nick Piggin , Peter Zijlstra , Mel Gorman , Andrew Morton List-ID: On Wed, 2008-07-30 at 12:16 +0900, Yasunori Goto wrote: > Well, I didn't mean changing pages_min value. There may be side effect as > you are saying. > I meant if some pages were MIGRATE_RESERVE attribute when hot-remove are > -executing-, their attribute should be changed. > > For example, how is like following dummy code? Is it impossible? > (Not only here, some places will have to be modified..) Right, this should be possible. I was somewhat wandering from the subject, because I noticed that there may be a bigger problem with MIGRATE_RESERVE pages in ZONE_MOVABLE, and that we may not want to have them in the first place. The more memory we add to ZONE_MOVABLE, the less reserved pages will remain to the other zones. In setup_per_zone_pages_min(), min_free_kbytes will be redistributed to a zone where the kernel cannot make any use of it, effectively reducing the available min_free_kbytes. This just doesn't sound right. I believe that a similar situation is the reason why highmem pages are skipped in the calculation and I think that we need that for ZONE_MOVABLE too. Any thoughts on that problem? Setting pages_min to 0 for ZONE_MOVABLE, while not capping pages_low and pages_high, could be an option. I don't have a sufficient memory managment overview to tell if that has negative side effects, maybe someone with a deeper insight could comment on that. Thanks, Gerald -- 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