Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758091AbXKCTdS (ORCPT ); Sat, 3 Nov 2007 15:33:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755565AbXKCTdH (ORCPT ); Sat, 3 Nov 2007 15:33:07 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:50634 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755402AbXKCTdG (ORCPT ); Sat, 3 Nov 2007 15:33:06 -0400 Date: Sat, 3 Nov 2007 12:33:01 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Hugh Dickins cc: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] slub: fix Objects count In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1210 Lines: 38 On Sat, 3 Nov 2007, Hugh Dickins wrote: > I was afraid you might say something like that. > Perhaps it'll be a patch I need to use in my own builds. > Though I'd have thought others would want that accuracy too. > Didn't SLAB give it? (The "r*gr*ss**n" word!) Slab also only counts objects that are not in the queues. See free_block() f.e. We could improve the situation by flushing all cpu slabs before counts are determined. Which can be done manually. Run slabinfo -s and then look at the numbers. > > Adds to much overhead to the fast paths > > You've come to that conclusion very quickly! I have just spend a few weeks optimizing the fast and slow paths and there is some additional overhead that I am still trying to eliminate. > Any numbers to back it up? The performance in the fast paths depends on updating only a single word for an allocation. Adding another counter makes that impossible. See the recent post on SLUB regression on SMP. - 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/