From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [PATCH 16/17] fs: Convert nr_inodes to a per-cpu counter Date: Thu, 30 Sep 2010 16:10:39 +1000 Message-ID: <20100930061039.GX5665@dastard> References: <1285762729-17928-1-git-send-email-david@fromorbit.com> <1285762729-17928-17-git-send-email-david@fromorbit.com> <20100929215322.ff635d3e.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Andrew Morton Return-path: Received: from bld-mail18.adl2.internode.on.net ([150.101.137.103]:33758 "EHLO mail.internode.on.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753788Ab0I3GKo (ORCPT ); Thu, 30 Sep 2010 02:10:44 -0400 Content-Disposition: inline In-Reply-To: <20100929215322.ff635d3e.akpm@linux-foundation.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Sep 29, 2010 at 09:53:22PM -0700, Andrew Morton wrote: > On Wed, 29 Sep 2010 22:18:48 +1000 Dave Chinner wrote: > > > From: Eric Dumazet > > > > The number of inodes allocated does not need to be tied to the > > addition or removal of an inode to/from a list. If we are not tied > > to a list lock, we could update the counters when inodes are > > initialised or destroyed, but to do that we need to convert the > > counters to be per-cpu (i.e. independent of a lock). This means that > > we have the freedom to change the list/locking implementation > > without needing to care about the counters. > > > > > > ... > > > > +int get_nr_inodes(void) > > +{ > > + int i; > > + int sum = 0; > > + for_each_possible_cpu(i) > > + sum += per_cpu(nr_inodes, i); > > + return sum < 0 ? 0 : sum; > > +} > > This reimplements percpu_counter_sum_positive(), rather poorly I thought so - it was on my list of things to check when redoing this patch. I'll fix that up appropritately. > > If one never intends to use the approximate percpu_counter_read() then > one could initialise the counter with a really large batch value, for a > very small performance gain. > > > +int get_nr_inodes_unused(void) > > +{ > > + return inodes_stat.nr_unused; > > +} > > > > ... > > > > @@ -407,6 +407,8 @@ extern struct files_stat_struct files_stat; > > extern int get_max_files(void); > > extern int sysctl_nr_open; > > extern struct inodes_stat_t inodes_stat; > > +extern int get_nr_inodes(void); > > +extern int get_nr_inodes_unused(void); > > These are pretty cruddy names. Unfotunately we don't really have a vfs > or "inode" subsystem name to prefix them with. Will fix. Cheers, Dave. -- Dave Chinner david@fromorbit.com