From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: Page allocator: Single Zone optimizations From: Peter Zijlstra In-Reply-To: References: <20061027190452.6ff86cae.akpm@osdl.org> <20061027192429.42bb4be4.akpm@osdl.org> <20061027214324.4f80e992.akpm@osdl.org> <20061028180402.7c3e6ad8.akpm@osdl.org> <4544914F.3000502@yahoo.com.au> <20061101182605.GC27386@skynet.ie> <20061101123451.3fd6cfa4.akpm@osdl.org> <454A2CE5.6080003@shadowen.org> <1162558085.26989.17.camel@twins> Content-Type: text/plain Date: Fri, 03 Nov 2006 19:53:03 +0100 Message-Id: <1162579983.26989.27.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Mel Gorman , Andy Whitcroft , Andrew Morton , Nick Piggin , KAMEZAWA Hiroyuki , Linux Memory Management List List-ID: On Fri, 2006-11-03 at 10:15 -0800, Christoph Lameter wrote: > On Fri, 3 Nov 2006, Peter Zijlstra wrote: > > > > I think talking about reclaim here is not what you want. > > > > I think it is; all of this only matters at the moment you want to > > allocate a large page, at that time you need to reclaim memory to > > satisfy the request. (There is some hysteresis between alloc and > > reclaim; but lets ignore that for a moment.) > > That is wrong. Dropping pages that will later have to be reread is not > good. It is better to defrag by moving pages. > > The ability to move pages about that are otherwise unreclaimable does > > indeed open up a new class of pages. But moving pages about is not the > > main purpose; attaining linear free pages with the least amount of > > collateral damage is. > > IMHO Moving pages creates less collateral damage than evicting > random pages. Move them where?, you have to drop pages anyway, the only thing migrate_pages() (my bad for calling it move_pages()) might help with is preserving LRU order better and the possibility to move otherwise unreclaimable pages to a more favourable position (page-tables, mlock'ed). -- 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