From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 3 Nov 2006 10:15:02 -0800 (PST) From: Christoph Lameter Subject: Re: Page allocator: Single Zone optimizations In-Reply-To: <1162558085.26989.17.camel@twins> Message-ID: 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: Mel Gorman , Andy Whitcroft , Andrew Morton , Nick Piggin , KAMEZAWA Hiroyuki , Linux Memory Management List List-ID: 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. > So, the basic operation is reclaim, make it succeed in freeing up the > requested order page (with the least possible disturbance to the rest). It may lead to rereading of the page. > Moving memory about is not the point; although it might come in handy; > its freeing linear chunks of memory without disturbing too much. Freeing pages that we have to reread? > Sure, defrag or rather move_pages() could be rather useful. We have migrate_pages() for exactly that purpose. > 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. -- 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