From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 5 Dec 2006 08:14:58 -0800 (PST) From: Christoph Lameter Subject: Re: [PATCH] Add __GFP_MOVABLE for callers to flag allocations that may be migrated In-Reply-To: Message-ID: References: <20061130170746.GA11363@skynet.ie> <20061130173129.4ebccaa2.akpm@osdl.org> <20061201110103.08d0cf3d.akpm@osdl.org> <20061204140747.GA21662@skynet.ie> <20061204113051.4e90b249.akpm@osdl.org> <20061204143435.6ab587db.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Mel Gorman Cc: Andrew Morton , Andy Whitcroft , Linux Memory Management List , Linux Kernel Mailing List List-ID: On Mon, 4 Dec 2006, Mel Gorman wrote: > 4. Offlining a DIMM > 5. Offlining a Node > > For Situation 4, a zone may be needed because MAX_ORDER_NR_PAGES would have > to be set to too high for anti-frag to be effective. However, zones would > have to be tuned at boot-time and that would be an annoying restriction. If > DIMMs are being offlined for power reasons, it would be sufficient to be > best-effort. We are able to depopularize a portion of the pages in a MAX_ORDER chunk if the page structs pages on the borders of that portion are not stored on the DIMM. Set a flag in the page struct of those page struct pages straddling the border and free the page struct pages describing only memory in the DIMM. > Situation 5 requires that a hotpluggable node only allows __GFP_MOVABLE > allocations in the zonelists. This would probably involving having one > zone that only allowed __GFP_MOVABLE. This is *node* hotplug and we already have a node/zone structure etc where we could set some option to require only movable allocations. Note that NUMA nodes have always had only a single effective zone. There are some exceptions on some architectures where we have additional DMA zones on the first or first two nodes but NUMA memory policies will *not* allow to exercise control over allocations from those zones. > In other words, to properly address all situations, we may need anti-frag > and zones, not one or the other. I still do not see a need for additional zones. -- 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