Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753494AbbFDMhN (ORCPT ); Thu, 4 Jun 2015 08:37:13 -0400 Received: from mail-wi0-f170.google.com ([209.85.212.170]:33802 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752485AbbFDMhH (ORCPT ); Thu, 4 Jun 2015 08:37:07 -0400 Date: Thu, 4 Jun 2015 14:37:02 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Thomas Gleixner , umgwanakikbuti@gmail.com, mingo@elte.hu, ktkhai@parallels.com, rostedt@goodmis.org, juri.lelli@gmail.com, pang.xunlei@linaro.org, oleg@redhat.com, wanpeng.li@linux.intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 8/9] hrtimer: Allow hrtimer::function() to free the timer Message-ID: <20150604123702.GA10314@gmail.com> References: <20150603132903.203333087@infradead.org> <20150603134023.156059118@infradead.org> <20150603212949.GD3644@twins.programming.kicks-ass.net> <20150604055930.GA13638@gmail.com> <20150604100741.GG3644@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150604100741.GG3644@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1313 Lines: 37 * Peter Zijlstra wrote: > On Thu, Jun 04, 2015 at 07:59:30AM +0200, Ingo Molnar wrote: > > > > --- a/include/linux/hrtimer.h > > > +++ b/include/linux/hrtimer.h > > > @@ -123,8 +123,10 @@ struct hrtimer_sleeper { > > > > > > #ifdef CONFIG_64BIT > > > # define HRTIMER_CLOCK_BASE_ALIGN 64 > > > +# define __timer_base_running(timer) timer->base->running > > > #else > > > # define HRTIMER_CLOCK_BASE_ALIGN 32 > > > +# define __timer_base_running(timer) timer->base->cpu_base->running > > > #endif > > > > Please put it into the cpu_base on 64-bit as well: the base pointer is available > > already on 64-bit so there should be no measurable performance difference, and > > readability is a primary concern with all this code. > > That's an extra pointer chase for no reason :-( Only if we otherwise don't dereference cpu_base - is that the case in the relevant code paths? If we already dereference cpu_base (say for the lock) and have its value loaded then it's totally equivalent to chasing down it in base->. Thanks, Ingo -- 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/