From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764853AbXKTVu7 (ORCPT ); Tue, 20 Nov 2007 16:50:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758600AbXKTVuv (ORCPT ); Tue, 20 Nov 2007 16:50:51 -0500 Received: from tomts13.bellnexxia.net ([209.226.175.34]:64626 "EHLO tomts13-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757231AbXKTVuu (ORCPT ); Tue, 20 Nov 2007 16:50:50 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Ah4FAJLlQkdMROHU/2dsb2JhbACBWw Date: Tue, 20 Nov 2007 16:50:48 -0500 From: Mathieu Desnoyers To: Trond Myklebust Cc: Christoph Lameter , ak@suse.de, akpm@linux-foundation.org, travis@sgi.com, linux-kernel@vger.kernel.org Subject: Re: [rfc 19/45] cpu alloc: NFS statistics Message-ID: <20071120215048.GA14522@Krystal> References: <20071120011132.143632442@sgi.com> <20071120011336.210236732@sgi.com> <20071120130201.GE10127@Krystal> <1195592198.7234.45.camel@heimdal.trondhjem.org> <20071120212834.GC11291@Krystal> <1195595283.7234.50.camel@heimdal.trondhjem.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <1195595283.7234.50.camel@heimdal.trondhjem.org> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 16:49:26 up 17 days, 2:54, 6 users, load average: 1.33, 1.27, 1.48 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Trond Myklebust (trond.myklebust@fys.uio.no) wrote: > > On Tue, 2007-11-20 at 16:28 -0500, Mathieu Desnoyers wrote: > > * Trond Myklebust (trond.myklebust@fys.uio.no) wrote: > > > > > > On Tue, 2007-11-20 at 12:49 -0800, Christoph Lameter wrote: > > > > On Tue, 20 Nov 2007, Mathieu Desnoyers wrote: > > > > > > > > > > Index: linux-2.6/fs/nfs/iostat.h > > > > > > =================================================================== > > > > > > --- linux-2.6.orig/fs/nfs/iostat.h 2007-11-15 21:17:24.391404458 -0800 > > > > > > +++ linux-2.6/fs/nfs/iostat.h 2007-11-15 21:25:33.167654066 -0800 > > > > > > @@ -123,7 +123,7 @@ static inline void nfs_inc_server_stats( > > > > > > int cpu; > > > > > > > > > > > > cpu = get_cpu(); > > > > > > - iostats = per_cpu_ptr(server->io_stats, cpu); > > > > > > + iostats = CPU_PTR(server->io_stats, cpu); > > > > > > iostats->events[stat] ++; > > > > > > > > > > Is there a way to change this into a CPU_ADD ? > > > > > > > > Yes I must have missed that. > > > > > > > > Could be > > > > > > > > CPU_INC(server->io_stats->events[stat]); > > > > > > > > > > > > > > > put_cpu_no_resched(); > > > > > > > > > > Why put_cpu_no_resched here ? > > > > > > > > We do not want to reschedule here? We may have already disabled interrupts > > > > or some such thing. > > > > > > Some of these statistics are updated from inside a spinlocked > > > environment, hence the put_no_resched(). > > > > > > > The we could use __get_cpu_var instead ? (since we know preemption is > > _always_ disabled when we are called) ? > > We don't know that. I said that _some_ of these statistics are updated > in that way. > Then my original point is valid : put_no_resched() will cause unwanted scheduler latencies. It's designed only to be used from within the scheduler code itself. The correct approach would be a standard put_cpu(). Or am I missing something ? Mathieu > Cheers > Trond > -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68