From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763322AbXIXTZG (ORCPT ); Mon, 24 Sep 2007 15:25:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763153AbXIXTYc (ORCPT ); Mon, 24 Sep 2007 15:24:32 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:57707 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763136AbXIXTYa (ORCPT ); Mon, 24 Sep 2007 15:24:30 -0400 Date: Mon, 24 Sep 2007 20:24:26 +0100 From: Christoph Hellwig To: Andrew Morton Cc: Christoph Hellwig , Dave Hansen , linux-kernel@vger.kernel.org, xfs@oss.sgi.com Subject: Re: [PATCH 24/25] r/o bind mounts: track number of mount writers Message-ID: <20070924192425.GA6629@infradead.org> Mail-Followup-To: Christoph Hellwig , Andrew Morton , Dave Hansen , linux-kernel@vger.kernel.org, xfs@oss.sgi.com References: <20070920195249.852667D5@kernel> <20070920195320.38C8E20D@kernel> <20070924175411.GA2314@infradead.org> <20070924121035.8d8c6ce2.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070924121035.8d8c6ce2.akpm@linux-foundation.org> User-Agent: Mutt/1.4.2.3i X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 24, 2007 at 12:10:35PM -0700, Andrew Morton wrote: > > As we already say in various messages the percpu counters in here > > look rather fishy. I'd recomment to take a look at the per-cpu > > superblock counters in XFS as they've been debugged quite well > > now and could probably be lifted into a generic library for this > > kind of think. The code is mostly in fs/xfs/xfs_mount.c can > > can be spotted by beeing under #ifdef HAVE_PERCPU_SB. > > > > It also handles cases like hotplug cpu nicely that this code > > seems to work around by always iterating over all possible cpus > > which might not be nice on a dual core laptop with a distro kernel > > that also has to support big iron. > > hm. How come xfs invented a new version of percpu_counters? This code actually predates the generic percpu_counters even if it was merged to mainline later. Neither Dave who wrote it nor me who reviewed it before it was merged thought of percpu_counters probably. Then again this code is considerably more complex due to features actually needed in a very hot fastpath.