Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756634AbZCVXDm (ORCPT ); Sun, 22 Mar 2009 19:03:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754590AbZCVXDb (ORCPT ); Sun, 22 Mar 2009 19:03:31 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:33833 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753589AbZCVXDb (ORCPT ); Sun, 22 Mar 2009 19:03:31 -0400 Date: Sun, 22 Mar 2009 16:03:31 -0700 From: "Paul E. McKenney" To: Arjan van de Ven Cc: Eric Dumazet , dipankar@in.ibm.com, linux-input@vger.kernel.org, dmitry.torokhov@gmail.com, linux-kernel@vger.kernel.org Subject: Re: Question about usage of RCU in the input layer Message-ID: <20090322230331.GM7148@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20090321210745.GE7148@linux.vnet.ibm.com> <20090321204045.4a9022fd@infradead.org> <20090322043838.GF7148@linux.vnet.ibm.com> <20090321215109.717a3f12@infradead.org> <20090322051822.GG7148@linux.vnet.ibm.com> <20090321225318.5b25f0a7@infradead.org> <20090322165324.GH7148@linux.vnet.ibm.com> <20090322124632.5d5d6266@infradead.org> <20090322205212.GI7148@linux.vnet.ibm.com> <20090322154433.1b2cb1b1@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090322154433.1b2cb1b1@infradead.org> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1565 Lines: 39 On Sun, Mar 22, 2009 at 03:44:33PM -0700, Arjan van de Ven wrote: > On Sun, 22 Mar 2009 13:52:12 -0700 > "Paul E. McKenney" wrote: > > > On Sun, Mar 22, 2009 at 12:46:32PM -0700, Arjan van de Ven wrote: > > > On Sun, 22 Mar 2009 09:53:24 -0700 > > > "Paul E. McKenney" wrote: > > > > > > > > > How many synchronize_rcu() calls are you seeing on the boot > > > > > > path? > > > > > > > > > > I see 20 that hit the above code path (eg ones that wait) until > > > > > userspace starts. > > > > > > > > So with well-behaved readers, the full sequence would be worth > > > > something like 50-60 milliseconds. > > > > > > yeah it's about 10% if the total kernel boot time.. so it does > > > start to matter > > > > Half-second boot, eh? That would indeed be impressive. > > half a second until calling init.. that's what I have today (with all > drivers built in).. nothing really special needed for it > (well a few small patches that are pending for 2.6.30 ;-) I thought the measurement was until the desktop was running with no more disk activity. ;-) But in any case, I will see what I can do about speeding up synchronize_rcu(). I will likely start with TREE_RCU, and I may need some sort of indication that boot is in progress. Thanx, Paul -- 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/