From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH 00/03] Unmapped: Separate unmapped and mapped pages From: Peter Zijlstra In-Reply-To: References: <20060310034412.8340.90939.sendpatchset@cherry.local> <1141993351.8165.10.camel@twins> Content-Type: text/plain Date: Sat, 11 Mar 2006 22:08:15 +0100 Message-Id: <1142111295.2928.14.camel@lappy> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Magnus Damm Cc: Peter Zijlstra , Magnus Damm , Linux Kernel , linux-mm@kvack.org List-ID: On Fri, 2006-03-10 at 14:38 +0100, Magnus Damm wrote: > On 3/10/06, Peter Zijlstra wrote: > > Breaking the LRU in two like this breaks the page ordering, which makes > > it possible for pages to stay resident even though they have much less > > activity than pages that do get reclaimed. > > Yes, true. But this happens already with a per-zone LRU. LRU pages > that happen to end up in the DMA zone will probably stay there a > longer time than pages in the normal zone. That does not mean it is > right to break the page ordering though, I'm just saying it happens > already and the oldest piece of data in the global system will not be > reclaimed first - instead there are priorities such as unmapped pages > will be reclaimed over mapped and so on. (I strongly feel that there > should be per-node LRU:s, but that's another story) If reclaim works right* there is equal pressure on each zone (proportional to their size) and hence each page will have an equal life time expectancy. (*) this is of course not possible for all workloads, however balance_pgdat and the page allocator take pains to make it as true as possible. Peter -- 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