From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 14 May 2007 11:12:24 -0500 From: Matt Mackall Subject: Re: [PATCH 0/5] make slab gfp fair Message-ID: <20070514161224.GC11115@waste.org> References: <20070514131904.440041502@chello.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Thomas Graf , David Miller , Andrew Morton , Daniel Phillips , Pekka Enberg List-ID: On Mon, May 14, 2007 at 08:53:21AM -0700, Christoph Lameter wrote: > On Mon, 14 May 2007, Peter Zijlstra wrote: > > > In the interest of creating a reserve based allocator; we need to make the slab > > allocator (*sigh*, all three) fair with respect to GFP flags. > > I am not sure what the point of all of this is. > > > That is, we need to protect memory from being used by easier gfp flags than it > > was allocated with. If our reserve is placed below GFP_ATOMIC, we do not want a > > GFP_KERNEL allocation to walk away with it - a scenario that is perfectly > > possible with the current allocators. > > Why does this have to handled by the slab allocators at all? If you have > free pages in the page allocator then the slab allocators will be able to > use that reserve. If I understand this correctly: privileged thread unprivileged greedy process kmem_cache_alloc(...) adds new slab page from lowmem pool do_io() kmem_cache_alloc(...) kmem_cache_alloc(...) kmem_cache_alloc(...) kmem_cache_alloc(...) kmem_cache_alloc(...) ... eats it all kmem_cache_alloc(...) -> ENOMEM who ate my donuts?! But I think this solution is somehow overkill. If we only care about this issue in the OOM avoidance case, then our rank reduces to a boolean. -- Mathematics is the supreme nostalgia of our time. -- 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