From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755773Ab2DNR0B (ORCPT ); Sat, 14 Apr 2012 13:26:01 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:34226 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752812Ab2DNR0A (ORCPT ); Sat, 14 Apr 2012 13:26:00 -0400 Date: Sat, 14 Apr 2012 10:25:04 -0700 From: "Paul E. McKenney" To: Linus Torvalds Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org Subject: Re: [PATCH RFC 0/7] rcu: v2 Inlinable preemptible rcu_read_lock() and rcu_read_unlock() Message-ID: <20120414172504.GH2452@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120414161953.GA18140@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12041417-7282-0000-0000-000008302D96 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 14, 2012 at 10:08:54AM -0700, Linus Torvalds wrote: > On Sat, Apr 14, 2012 at 9:58 AM, Linus Torvalds > wrote: > > > > I'll see if it boots and what it does to my profiles and > > microbenchmark, though. > > Ok, I can't see any performance difference in the numbers - my > benchmark noise is *much* bigger than anything this would show. Might still be worthwhile on embedded CPUs that don't optimize function calls as thoroughly as does x86, maybe? > The profile looks fine, and obviously __rcu_read_lock() is entirely > gone. The top user (avc_has_perm_flags()) looks fine. I note that you > might want to look at the placement of the percpu data - I think it > probably makes sense to put the RCU data close to 'current' etc to get > as much cacheline sharing as possible, and it doesn't seem to be right > now, but it looks reasonable. Is there somewhere in non-architecture-specific code that would be a good place to put this? Or is the DEFINE_PER_CPU() for current_task moving from arch/x86 to core code? > But on the whole, I can't claim that it looks noticeable ;*( Well, then, I guess I don't feel quite so bad about having prioritized this so low for so long. ;-) Thanx, Paul