From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 1 Mar 2008 11:58:46 +0200 (EET) From: Pekka J Enberg Subject: Re: [patch 6/8] slub: Adjust order boundaries and minimum objects per slab. In-Reply-To: Message-ID: References: <20080229044803.482012397@sgi.com> <20080229044819.800974712@sgi.com> <47C7BFFA.9010402@cs.helsinki.fi> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Mel Gorman , Matt Mackall , linux-mm@kvack.org List-ID: Hi Christoph, On Fri, 29 Feb 2008, Pekka Enberg wrote: > > I can see why you want to change the defaults for big iron but why not keep > > the existing PAGE_SHIFT check which leaves embedded and regular desktop > > unchanged? On Fri, 29 Feb 2008, Christoph Lameter wrote: > The defaults for slab are also 60 objects per slab. The PAGE_SHIFT says > nothing about the big iron. Our new big irons have a page shift of 12 and > are x86_64. Where is that objects per slab limit? I only see calculate_slab_order() trying out bunch of page orders until we hit "acceptable" internal fragmentation. Also keep in mind how badly SLAB compares to SLUB and SLOB in terms of memory efficiency. Maybe we can use total amount of memory as some sort of heuristic to determine the defaults? That way boxes with lots of memory get to use larger orders for better performance whereas smaller boxes are more memory efficient. On Fri, 29 Feb 2008, Christoph Lameter wrote: > We could drop the limit if CONFIG_EMBEDDED is set but then this may waste > space. A higher order allows slub to reach a higher object density (in > particular for objects 500-2000 bytes size). I am more worried about memory allocated for objects that are not used rather than memory wasted due to bad fitting. Pekka -- 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