From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 21 Nov 2007 14:28:04 -0800 (PST) From: Christoph Lameter Subject: Re: [PATCH] Page allocator: Get rid of the list of cold pages In-Reply-To: <20071121222059.GC31674@csn.ul.ie> Message-ID: References: <20071115162706.4b9b9e2a.akpm@linux-foundation.org> <20071121222059.GC31674@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Mel Gorman Cc: Andrew Morton , linux-mm@kvack.org, apw@shadowen.org, Martin Bligh List-ID: On Wed, 21 Nov 2007, Mel Gorman wrote: > 1. In general, the split lists are faster than the combined list > 2. Disabling Per-CPU has comparable performance to having the lists That is only true for the single threaded case (actually I am measuring a slight performance benefit if I switch them off). If you have multiple processes allocating from the same zone then you can get the zone locks hot. That was the reason for the recent regression in SLUB. The networking layer went from an order 0 alloc to order 1. Zonelock contention then dropped performance by 50% on an 8p! The potential for lock contention is higher the more processor per nodeare involved. So you are not going to see this as high on a standard NUMA config with 2p per node. The main point at this juncture of the pcp lists seems to be avoiding zone lock contention! The overhead of extracting a page from the buddy lists is not such a problem. > single-pcplist-batch8: This is Christophs patch with pcp->high == 8*batch > as suggested by Martin Bligh (I agreed with him that keeping lists > the same size made sense) Ack. I have not had a look at the details of your performance measurements yet. More later. -- 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