From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: NUMA policy issues with ZONE_MOVABLE From: Lee Schermerhorn In-Reply-To: References: Content-Type: text/plain Date: Wed, 25 Jul 2007 10:27:01 -0400 Message-Id: <1185373621.5604.28.camel@localhost> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: linux-mm@kvack.org, ak@suse.de, KAMEZAWA Hiroyuki , Mel Gorman , akpm@linux-foundation.org List-ID: On Tue, 2007-07-24 at 21:20 -0700, Christoph Lameter wrote: > The outcome of the 2.6.23 merge was surprising. No antifrag but only > ZONE_MOVABLE. ZONE_MOVABLE is the highest zone. > > For the NUMA layer this has some weird consequences if ZONE_MOVABLE is populated > > 1. It is the highest zone. > > 2. Thus policy_zone == ZONE_MOVABLE > > ZONE_MOVABLE contains only movable allocs by default. That is anonymous > pages and page cache pages? > > The NUMA layer only supports NUMA policies for the highest zone. > Thus NUMA policies can control anonymous pages and the page cache pages > allocated from ZONE_MOVABLE. > > However, NUMA policies will no longer affect non pagecache and non > anonymous allocations. So policies can no longer redirect slab allocations > and huge page allocations (unless huge page allocations are moved to > ZONE_MOVABLE). And there are likely other allocations that are not > movable. > > If ZONE_MOVABLE is off then things should be working as normal. > > Doesnt this mean that ZONE_MOVABLE is incompatible with CONFIG_NUMA? > > > The mobility approach used subcategories of a zone which would have > allowed the application of memory policies. Isn't ZONE_MOVABLE always a subset of the memory in the highest "real" zone--the one that WOULD be policy_zone if ZONE_MOVABLE weren't configured? If so, perhaps we could just not assign ZONE_MOVABLE to policy_zone in check_highest zone. We already check for >= or < policy_zone where it's checked [zonelist_policy() and vma_migratable()], so ZONE_MOVABLE will get a free pass if we clip policy_zone at the highest !MOVABLE zone. Lee -- 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