From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 520DC620202 for ; Tue, 25 May 2010 11:38:04 -0400 (EDT) Date: Wed, 26 May 2010 01:37:59 +1000 From: Nick Piggin Subject: Re: [RFC V2 SLEB 00/14] The Enhanced(hopefully) Slab Allocator Message-ID: <20100525153759.GA20853@laptop> References: <20100521211452.659982351@quilx.com> <20100524070309.GU2516@laptop> <20100525020629.GA5087@laptop> <20100525143409.GP5087@laptop> <20100525151129.GS5087@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: Christoph Lameter , Pekka Enberg , linux-mm@kvack.org, Linus Torvalds List-ID: On Tue, May 25, 2010 at 10:28:11AM -0500, Christoph Lameter wrote: > On Wed, 26 May 2010, Nick Piggin wrote: > > > You do not understand. There is nothing *preventing* other designs of > > allocators from using higher order allocations. The problem is that > > SLUB is *forced* to use them due to it's limited queueing capabilities. > > SLUBs use of higher order allocation is *optional*. The limited queuing is > advantageous within the framework of SLUB because NUMA locality checks are > simplified and locking is localized to a single page increasing > concurrency. It's not optional if performance sucks without it. People want to have a well performing slab allocator and also not have the downsides of it using higher order allocations. Look at what David said about Google's kernel for a concrete example. > > You keep spinning this as a good thing for SLUB design when it is not. > > It is a good design decision. You have an irrational fear of higher order > allocations. No. > > > The reason that the alien caches made it into SLAB were performance > > > numbers that showed that the design "must" be this way. I prefer a clear > > > maintainable design over some numbers (that invariably show the bias of > > > the tester for certain loads). > > > > I don't really agree. There are a number of other possible ways to > > improve it, including fewer remote freeing queues. > > You disagree with the history of the allocator? I don't agree with you saying that it "must" be that way. There are other ways to improve things there. > > How is it possibly better to instead start from the known suboptimal > > code and make changes to it? What exactly is your concern with > > making incremental changes to SLAB? > > I am not sure why you want me to repeat what I already said. Guess we > should stop this conversation since it is deteriorating. You never answered these questions adequately. These are the 2 most important things because if I can address your concerns with them, then we can go ahead and throw out SLUB and make incremental improvements from there instead. -- 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