From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH 00/10] foundations for reserve-based allocation From: Peter Zijlstra In-Reply-To: <200708061231.04982.phillips@phunq.net> References: <20070806102922.907530000@chello.nl> <200708061035.18742.phillips@phunq.net> <1186424248.11797.66.camel@lappy> <200708061231.04982.phillips@phunq.net> Content-Type: text/plain Date: Mon, 06 Aug 2007 21:36:58 +0200 Message-Id: <1186429018.11797.100.camel@lappy> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Daniel Phillips Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Miller , Andrew Morton , Daniel Phillips , Pekka Enberg , Christoph Lameter , Matt Mackall , Lee Schermerhorn , Steve Dickson List-ID: On Mon, 2007-08-06 at 12:31 -0700, Daniel Phillips wrote: > On Monday 06 August 2007 11:17, Peter Zijlstra wrote: > > And how do we know a page was taken out of the reserves? > > Why not return that in the low bit of the page address? This is a > little more cache efficient, does not leave that odd footprint in the > page union and forces the caller to examine the > alloc_pages(...P_MEMALLOC) return, making it harder to overlook the > fact that it got a page out of reserve and forget to put one back > later. This would require auditing all page allocation sites to ensure they ever happen under PF_MEMALLOC or the like. Because if an allocator ever fails to check the low bit and assumes its a valid struct page *, stuff will go *bang*. -- 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