From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751886AbbDIGjy (ORCPT ); Thu, 9 Apr 2015 02:39:54 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:33452 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751798AbbDIGjw (ORCPT ); Thu, 9 Apr 2015 02:39:52 -0400 Date: Thu, 9 Apr 2015 08:39:47 +0200 From: Ingo Molnar To: Thomas Gleixner Cc: Viresh Kumar , Ingo Molnar , Peter Zijlstra , linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org, Preeti U Murthy Subject: [PATCH] hrtimer: Only iterate over active bases in migrate_hrtimers() Message-ID: <20150409063947.GD14259@gmail.com> References: <20150409062841.GB14259@gmail.com> <20150409063838.GC14259@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150409063838.GC14259@gmail.com> 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 (fixed the subject to include the patch title. Patch quoted below.) * Ingo Molnar wrote: > > * Ingo Molnar wrote: > > > This would speed up various hrtimer primitives like > > hrtimer_remove()/add and simplify the code. It would be a net code > > shrink as well. > > > > Totally untested patch below. It gives: > > > > text data bss dec hex filename > > 7502 427 0 7929 1ef9 hrtimer.o.before > > 7422 427 0 7849 1ea9 hrtimer.o.after > > > > and half of that code removal is from hot paths. > > > > This would simplify the followup step of skipping over inactive bases > > as well. > > The followup step is attached below (untested as well). > > Note that all other iterations already had a check for active.next, so > the patch doesn't even bloat anything: > > text data bss dec hex filename > 7422 427 0 7849 1ea9 hrtimer.o.before > 7422 427 0 7849 1ea9 hrtimer.o.after > > (I did a rename within migrate_hrtimers() because it used 'cpu_base' > vs 'clock_base' inconsistently in a confusing (to me) manner.) > > I'd also suggest the removal of the timerqueue_getnext() obfuscation: > it 'sounds' complex but in reality it's a simple dereference to > active.next. I think this is what triggered this rather pointless > maintenance of active_bases. > > Thanks, > > Ingo > > --- > kernel/time/hrtimer.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > Index: tip/kernel/time/hrtimer.c > =================================================================== > --- tip.orig/kernel/time/hrtimer.c > +++ tip/kernel/time/hrtimer.c > @@ -1660,29 +1660,35 @@ static void migrate_hrtimer_list(struct > > static void migrate_hrtimers(int scpu) > { > - struct hrtimer_cpu_base *old_base, *new_base; > + struct hrtimer_cpu_base *old_cpu_base, *new_cpu_base; > int i; > > BUG_ON(cpu_online(scpu)); > tick_cancel_sched_timer(scpu); > > local_irq_disable(); > - old_base = &per_cpu(hrtimer_bases, scpu); > - new_base = this_cpu_ptr(&hrtimer_bases); > + old_cpu_base = &per_cpu(hrtimer_bases, scpu); > + new_cpu_base = this_cpu_ptr(&hrtimer_bases); > /* > * The caller is globally serialized and nobody else > * takes two locks at once, deadlock is not possible. > */ > - raw_spin_lock(&new_base->lock); > - raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING); > + raw_spin_lock(&new_cpu_base->lock); > + raw_spin_lock_nested(&old_cpu_base->lock, SINGLE_DEPTH_NESTING); > > for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) { > - migrate_hrtimer_list(&old_base->clock_base[i], > - &new_base->clock_base[i]); > + struct hrtimer_clock_base *old_base = old_cpu_base->clock_base + i; > + struct hrtimer_clock_base *new_base; > + > + if (!old_base->active.next) > + continue; > + > + new_base = new_cpu_base->clock_base + i; > + migrate_hrtimer_list(old_base, new_base); > } > > - raw_spin_unlock(&old_base->lock); > - raw_spin_unlock(&new_base->lock); > + raw_spin_unlock(&old_cpu_base->lock); > + raw_spin_unlock(&new_cpu_base->lock); > > /* Check, if we got expired work to do */ > __hrtimer_peek_ahead_timers();