Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752272AbbFDF7r (ORCPT ); Thu, 4 Jun 2015 01:59:47 -0400 Received: from mail-wi0-f172.google.com ([209.85.212.172]:38783 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750896AbbFDF7h (ORCPT ); Thu, 4 Jun 2015 01:59:37 -0400 Date: Thu, 4 Jun 2015 07:59:30 +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: <20150604055930.GA13638@gmail.com> References: <20150603132903.203333087@infradead.org> <20150603134023.156059118@infradead.org> <20150603212949.GD3644@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150603212949.GD3644@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: 1767 Lines: 49 * Peter Zijlstra wrote: > On Wed, Jun 03, 2015 at 07:41:43PM +0200, Thomas Gleixner wrote: > > On Wed, 3 Jun 2015, Peter Zijlstra wrote: > > > /** > > > * struct hrtimer - the basic hrtimer structure > > > @@ -153,6 +144,7 @@ struct hrtimer_clock_base { > > > struct timerqueue_head active; > > > ktime_t (*get_time)(void); > > > ktime_t offset; > > > + struct hrtimer *running; > > > > Aside of lacking a KernelDoc comment, it expands the struct size on > > 32bit from 32 bytes to 36 bytes which undoes some of the recent cache > > line optimizations I did. Mooo! > > > > So we might think about storing the running timer pointer in cpu_base > > instead for 32bit, which increases the foot print of the migration > > base and the extra cost for the additional indirection, but it would > > keep cache line tight for the hot pathes. > > A wee something like this then? > > --- > --- 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. 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/