From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 4 Dec 2006 13:19:59 -0800 From: Andrew Morton Subject: Re: [PATCH] Add __GFP_MOVABLE for callers to flag allocations that may be migrated Message-Id: <20061204131959.bdeeee41.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> <20061204120611.4306024e.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 12:17:26 -0800 (PST) Christoph Lameter wrote: > > 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. > > Mel's approach already mananges memory in a chunks of MAX_ORDER. It is > easy to just restrict the unmovable types of allocation to a section of > the zone. What happens when we need to run reclaim against just a section of a zone? Lumpy-reclaim could be used here; perhaps that's Mel's approach too? We'd need new infrastructure to perform the section-of-a-zone<->physical-memory-block mapping, and to track various states of the section-of-a-zone. This will be complex, and buggy. It will probably require the introduction of some sort of "sub-zone" structure. At which stage people would be justified in asking "why didn't you just use zones - that's what they're for?" > Then we should be doing some work to cut down the number of unmovable > allocations. That's rather pointless. A feature is either reliable or it is not. We'll never be able to make all kernel allocations reclaimable/moveable so we'll never be reliable with this approach. I don't see any alternative to the never-allocate-kernel-objects-in-removeable-memory approach. -- 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