From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 11 Feb 2008 15:42:34 -0800 (PST) From: Christoph Lameter Subject: Re: SLUB tbench regression due to page allocator deficiency In-Reply-To: <20080211234029.GB14980@wotan.suse.de> Message-ID: References: <20080209143518.ced71a48.akpm@linux-foundation.org> <20080210024517.GA32721@wotan.suse.de> <20080211071828.GD8717@wotan.suse.de> <20080211234029.GB14980@wotan.suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Andrew Morton , Mel Gorman , linux-mm@kvack.org, Pekka J Enberg List-ID: On Tue, 12 Feb 2008, Nick Piggin wrote: > It might be possible but would take quite a bit of rework (eg. have a > look at pcp->count and the horrible anti fragmentation loops). Yeah. May influece the way we have to handle freelists. Sigh. > > The fastpath use will be reduced to 50% since every other > > allocation will have to go to the page allocator. Maybe we can do that > > if the page allocator performance is up to snuff. > > The page allocator has to do quite a lot more than the slab allocator > does. It has to check watermarks and all the NUMA and zone and anti > fragmentation stuff, and does quite a lot of branches and stores to > tes tand set up the struct page. > > So it's never going to be as fast as a simple slab allocation. Well but does it have to do all of that on *each* allocation? The slab allocators also do quite a number of things including NUMA handling but all of that is in the slow path and its not done for every single allocation. -- 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