From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH 0/5] make slab gfp fair From: Peter Zijlstra In-Reply-To: References: <20070514131904.440041502@chello.nl> Content-Type: text/plain Date: Mon, 14 May 2007 18:10:11 +0200 Message-Id: <1179159011.2942.16.camel@lappy> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Thomas Graf , David Miller , Andrew Morton , Daniel Phillips , Pekka Enberg , Matt Mackall List-ID: On Mon, 2007-05-14 at 08:53 -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. Yes, too freely. GFP flags are only ever checked when you allocate a new page. Hence, if you have a low reaching alloc allocating a slab page; subsequent non critical GFP_KERNEL allocs can fill up that slab. Hence you would need to reserve a slab per object instead of the normal packing. -- 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