Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753168AbZAZR0W (ORCPT ); Mon, 26 Jan 2009 12:26:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751595AbZAZR0I (ORCPT ); Mon, 26 Jan 2009 12:26:08 -0500 Received: from smtp.ultrahosting.com ([74.213.174.254]:56131 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751565AbZAZR0H (ORCPT ); Mon, 26 Jan 2009 12:26:07 -0500 Date: Mon, 26 Jan 2009 12:22:28 -0500 (EST) From: Christoph Lameter X-X-Sender: cl@qirst.com To: Peter Zijlstra cc: Pekka Enberg , Nick Piggin , Linux Memory Management List , Linux Kernel Mailing List , Andrew Morton , Lin Ming , "Zhang, Yanmin" Subject: Re: [patch] SLQB slab allocator (try 2) In-Reply-To: <1232960840.4863.7.camel@laptop> Message-ID: References: <20090123154653.GA14517@wotan.suse.de> <1232959706.21504.7.camel@penberg-laptop> <1232960840.4863.7.camel@laptop> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1133 Lines: 22 On Mon, 26 Jan 2009, Peter Zijlstra wrote: > Then again, anything that does allocation is per definition not bounded > and not something we can have on latency critical paths -- so on that > respect its not interesting. Well there is the problem in SLAB and SLQB that they *continue* to do processing after an allocation. They defer queue cleaning. So your latency critical paths are interrupted by the deferred queue processing. SLAB has the awful habit of gradually pushing objects out of its queued (tried to approximate the loss of cpu cache hotness over time). So for awhile you get hit every 2 seconds with some free operations to the page allocator on each cpu. If you have a lot of cpus then this may become an ongoing operation. The slab pages end up in the page allocator queues which is then occasionally pushed back to the buddy lists. Another relatively high spike there. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/