From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <46410DFB.2080507@yahoo.com.au> Date: Wed, 09 May 2007 09:55:39 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: SLUB: Reduce antifrag max order (fwd) References: <46407DD4.7080101@shadowen.org> In-Reply-To: <46407DD4.7080101@shadowen.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andy Whitcroft Cc: Mel Gorman , clameter@sgi.com, akpm@linux-foundation.org, Linux Memory Management List List-ID: Andy Whitcroft wrote: > Mel Gorman wrote: > >>Sorry for resend, I didn't add Andy to the cc as intended. >> >>On Sat, 5 May 2007, Christoph Lameter wrote: >> >> >>>My test systems fails to obtain order 4 allocs after prolonged use. >>>So the Antifragmentation patches are unable to guarantee order 4 >>>blocks after a while (straight compile, edit load). >>> >> >>Anti-frag still depends on reclaim to take place and I imagine you have >>not altered min_free_kbytes to keep pages free. Also, I don't think >>kswapd is currently making any effort to keep blocks free at a known >>desired order although I'm cc'ing Andy Whitcroft to confirm. As the >>kernel gives up easily when order > PAGE_ALLOC_COSTLY_ORDER, prehaps you >>should be using PAGE_ALLOC_COSTLY_ORDER instead of >>DEFAULT_ANTIFRAG_MAX_ORDER for SLUB. > > > kswapd only reactively uses orders above 0. If allocations are pushing > below the high water marks those will trigger kswapd to reclaim at their > highest order. No attempt overall is made to keep "some" higher order > pages free. It does try, if you have a look at zone_watermark_ok. But it doesn't check for pages of a higher order than are being allocated (ie. so an order-0 alloc could split the last free order-3 page). This is intentional, because if your workload isn't doing any higher order allocations, it should not be trying to keep any free. -- SUSE Labs, Novell Inc. -- 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