From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264852AbUEJQ17 (ORCPT ); Mon, 10 May 2004 12:27:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264855AbUEJQ17 (ORCPT ); Mon, 10 May 2004 12:27:59 -0400 Received: from bi01p1.co.us.ibm.com ([32.97.110.142]:4386 "EHLO linux.local") by vger.kernel.org with ESMTP id S264852AbUEJQ15 (ORCPT ); Mon, 10 May 2004 12:27:57 -0400 Date: Mon, 10 May 2004 09:26:45 -0700 From: "Paul E. McKenney" To: Matt Mackall Cc: Andrew Morton , arjanv@redhat.com, helgehaf@aitel.hist.no, linux-kernel@vger.kernel.org Subject: Re: dentry bloat. Message-ID: <20040510162645.GA1646@us.ibm.com> Reply-To: paulmck@us.ibm.com References: <20040508211920.GD4007@in.ibm.com> <20040508171027.6e469f70.akpm@osdl.org> <20040508201215.24f0d239.davem@redhat.com> <20040509210312.GL5414@waste.org> <409F3CEE.8060102@aitel.hist.no> <1084177928.4925.13.camel@laptop.fenrus.com> <20040510024658.53cb0b80.akpm@osdl.org> <20040510145403.GL28459@waste.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040510145403.GL28459@waste.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 10, 2004 at 09:54:04AM -0500, Matt Mackall wrote: > On Mon, May 10, 2004 at 02:46:58AM -0700, Andrew Morton wrote: > > Arjan van de Ven wrote: > > > > > > On Mon, 2004-05-10 at 10:27, Helge Hafting wrote: > > > > Matt Mackall wrote: > > > > > > > > >One also wonders about whether all the RCU stuff is needed on UP. I'm > > > > >not sure if I grok all the finepoints here, but it looks like the > > > > >answer is no and that we can make struct_rcu head empty and have > > > > >call_rcu fall directly through to the callback. This would save > > > > >something like 16-32 bytes (32/64bit), not to mention a bunch of > > > > >dinking around with lists and whatnot. > > > > > > > > > >So what am I missing? > > > > > > > > > > > > > > Preempt can happen anytime, I believe. > > > > > > ok so for UP-non-preempt we can still get those 16 bytes back from the > > > dentry.... > > > > I suppose so. And on small SMP, really. We chose not to play those games > > early on so the code got the best testing coverage. > > Ok, I can spin something up. I'll start with a generic no-RCU-on-UP > and then we can think about the small SMP case a bit later. Hello, Matt, You may wish to start with the dcache portion of Dipankar's earlier patch: http://sourceforge.net/mailarchive/forum.php?thread_id=3644163&forum_id=730 It does not remove the extra rcu_head from the dentry, but does the rest of the work. Thanx, Paul