From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 4 Dec 2006 12:06:11 -0800 From: Andrew Morton Subject: Re: [PATCH] Add __GFP_MOVABLE for callers to flag allocations that may be migrated Message-Id: <20061204120611.4306024e.akpm@osdl.org> In-Reply-To: References: <20061130170746.GA11363@skynet.ie> <20061130173129.4ebccaa2.akpm@osdl.org> <20061201110103.08d0cf3d.akpm@osdl.org> <20061204140747.GA21662@skynet.ie> <20061204113051.4e90b249.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Mel Gorman , Linux Memory Management List , Linux Kernel Mailing List List-ID: On Mon, 4 Dec 2006 11:41:42 -0800 (PST) Christoph Lameter wrote: > > That depends on how we do hot-unplug, if we do it. I continue to suspect > > that it'll be done via memory zones: effectively by resurrecting > > GFP_HIGHMEM. In which case there's little overlap with anti-frag. (btw, I > > have a suspicion that the most important application of memory hot-unplug > > will be power management: destructively turning off DIMMs). > > There are numerous other uses as well (besides DIMM and node unplug): > > 1. Faulty DIMM isolation > 2. Virtual memory managers can reduce memory without resorting to > balloons. > 3. Physical removal and exchange of memory while a system is running > (Likely necessary to complement hotplug cpu, cpus usually come > with memory). > > The multi zone approach does not work with NUMA. NUMA only supports a > single zone for memory policy control etc. Wot? memory policies are a per-vma thing? Plus NUMA of course supports more that a single zone. Perhaps you meant one zone per node. If you did, that's a pretty dumb-sounding restriction and I don't know where you got it from. > Also multiple zones carry with > it a management overhead that is unnecessary for the MOVABLE/UNMOVABLE > distinction. I suspect you'll have to live with that. I've yet to see a vaguely sane proposal to otherwise prevent unreclaimable, unmoveable kernel allocations from landing in a hot-unpluggable physical memory region. -- 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