From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: Question about usage of RCU in the input layer Date: Sun, 22 Mar 2009 13:52:12 -0700 Message-ID: <20090322205212.GI7148@linux.vnet.ibm.com> References: <20090321125115.0a76ac27@infradead.org> <49C54D60.80306@cosmosbay.com> <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> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e8.ny.us.ibm.com ([32.97.182.138]:53499 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753183AbZCVUwM (ORCPT ); Sun, 22 Mar 2009 16:52:12 -0400 Content-Disposition: inline In-Reply-To: <20090322124632.5d5d6266@infradead.org> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org 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 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. Thanx, Paul