Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758136AbcDHKsj (ORCPT ); Fri, 8 Apr 2016 06:48:39 -0400 Received: from casper.infradead.org ([85.118.1.10]:60830 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755900AbcDHKsi (ORCPT ); Fri, 8 Apr 2016 06:48:38 -0400 Date: Fri, 8 Apr 2016 12:48:21 +0200 From: Peter Zijlstra To: Frederic Weisbecker Cc: LKML , Byungchul Park , Chris Metcalf , Thomas Gleixner , Luiz Capitulino , Christoph Lameter , "Paul E . McKenney" , Mike Galbraith , Rik van Riel , Ingo Molnar Subject: Re: [PATCH 3/3] sched: Optimize !CONFIG_NO_HZ_COMMON cpu load updates Message-ID: <20160408104821.GM3448@twins.programming.kicks-ass.net> References: <1460077633-23431-1-git-send-email-fweisbec@gmail.com> <1460077633-23431-4-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1460077633-23431-4-git-send-email-fweisbec@gmail.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1775 Lines: 55 On Fri, Apr 08, 2016 at 03:07:13AM +0200, Frederic Weisbecker wrote: > index 4c522a7..59a2821 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7327,8 +7327,9 @@ void __init sched_init(void) > > for (j = 0; j < CPU_LOAD_IDX_MAX; j++) > rq->cpu_load[j] = 0; > - > +#ifdef CONFIG_NO_HZ_COMMON > rq->last_load_update_tick = jiffies; > +#endif > > #ifdef CONFIG_SMP > rq->sd = NULL; > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 1dd864d..4618e5b 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4661,8 +4680,10 @@ static inline void cpu_load_update_nohz(struct rq *this_rq, > > static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load) > { > +#ifdef CONFIG_NO_HZ_COMMON > /* See the mess around cpu_load_update_nohz(). */ > this_rq->last_load_update_tick = READ_ONCE(jiffies); > +#endif > cpu_load_update(this_rq, load, 1); > } > Here you do the simple #ifdef, while here you make a giant mess instead of the relatively straight forward: > @@ -4540,17 +4568,8 @@ static void cpu_load_update(struct rq *this_rq, unsigned long this_load, > > /* scale is effectively 1 << i now, and >> i divides by scale */ > > - old_load = this_rq->cpu_load[i]; #ifdef CONFIG_NO_HZ_COMMON > - old_load = decay_load_missed(old_load, pending_updates - 1, i); > - if (tickless_load) { > - old_load -= decay_load_missed(tickless_load, pending_updates - 1, i); > - /* > - * old_load can never be a negative value because a > - * decayed tickless_load cannot be greater than the > - * original tickless_load. > - */ > - old_load += tickless_load; > - } #endif > new_load = this_load; > /* > * Round up the averaging division if load is increasing. This