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 mtagate1.uk.ibm.com (8.13.8/8.13.8) with ESMTP id m71G4wZE055956 for ; Fri, 1 Aug 2008 16:04:58 GMT Received: from d06av01.portsmouth.uk.ibm.com (d06av01.portsmouth.uk.ibm.com [9.149.37.212]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v9.0) with ESMTP id m71G4vKT3940436 for ; Fri, 1 Aug 2008 17:04:57 +0100 Received: from d06av01.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av01.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m71G4uMG015972 for ; Fri, 1 Aug 2008 17:04:57 +0100 Subject: Re: memory hotplug: hot-add to ZONE_MOVABLE vs. min_free_kbytes From: Gerald Schaefer In-Reply-To: <20080801192646.EC99.E1E9C6FF@jp.fujitsu.com> References: <20080731132213.GF1704@csn.ul.ie> <1217526327.4643.35.camel@localhost.localdomain> <20080801192646.EC99.E1E9C6FF@jp.fujitsu.com> Content-Type: text/plain Date: Fri, 01 Aug 2008 18:04:55 +0200 Message-Id: <1217606695.5678.4.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Yasunori Goto Cc: Mel Gorman , 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 , Andrew Morton List-ID: On Fri, 2008-08-01 at 20:16 +0900, Yasunori Goto wrote: > > My assumption is now, that the reserved 3 MB in ZONE_MOVABLE won't be > > usable by the kernel anymore, e.g. for PF_MEMALLOC, because it is in > > ZONE_MOVABLE now. > > I don't make sense here. I suppose there is no relationship between > ZONE_MOVABLE, PF_MEMALLOC and MIGRATE_RESERVE pages. > Could you tell me more? Ok, I thought that PF_MEMALLOC allocations work on the MIGRATE_RESERVE pageblocks, and that only kernel allocations can use PF_MEMALLOC. I also thought that kernel allocations cannot use ZONE_MOVABLE, e.g. for page cache memory, because such pages would not be migratable. So I assumed that MIGRATE_RESERVE pageblocks in ZONE_MOVABLE would not be available for PF_MEMALLOC allocations. With this assumption, which can be totally wrong, the redistribution of MIGRATE_RESERVE pageblocks in setup_per_zone_pages_min() looks like it will take away reserved pageblocks that should be available to the kernel in emergency situations. Maybe I should have explained this assumption earlier, because my whole min_free_kbytes issue depends on it. If I'm wrong, I apologize for confusing you all with this "issue", and I will go back to the original problem with removing the lowest memory chunk in ZONE_MOVABLE... 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