From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758994AbaD3Nqx (ORCPT ); Wed, 30 Apr 2014 09:46:53 -0400 Received: from service87.mimecast.com ([91.220.42.44]:47052 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758939AbaD3Nqv convert rfc822-to-8bit (ORCPT ); Wed, 30 Apr 2014 09:46:51 -0400 Message-ID: <5360FECF.6060301@arm.com> Date: Wed, 30 Apr 2014 14:46:55 +0100 From: Dietmar Eggemann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Peter Zijlstra CC: "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] sched: Do not zero sg->cpumask and sg->sgp->power in build_sched_groups References: <1398865178-12577-1-git-send-email-dietmar.eggemann@arm.com> In-Reply-To: <1398865178-12577-1-git-send-email-dietmar.eggemann@arm.com> X-OriginalArrivalTime: 30 Apr 2014 13:47:03.0758 (UTC) FILETIME=[AB2B8EE0:01CF647A] X-MC-Unique: 114043014465000501 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/04/14 14:39, Dietmar Eggemann wrote: > From: Dietmar Eggemann > > There is no need to zero struct sched_group member cpumask and struct > sched_group_power member power since both structures are already allocated > as zeroed memory in __sdt_alloc(). > > This patch has been tested with > BUG_ON(!cpumask_empty(sched_group_cpus(sg))); and BUG_ON(sg->sgp->power); > in build_sched_groups() on ARM TC2 and INTEL i5 M520 platform including > CPU hotplug scenarios. > > Signed-off-by: Dietmar Eggemann > --- > kernel/sched/core.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 9cae286824bb..6bc51aebbf1b 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -5807,8 +5807,6 @@ build_sched_groups(struct sched_domain *sd, int cpu) > continue; > > group = get_group(i, sdd, &sg); > - cpumask_clear(sched_group_cpus(sg)); > - sg->sgp->power = 0; > cpumask_setall(sched_group_mask(sg)); > > for_each_cpu(j, span) { > there is also a discrepancy between build_sched_groups() and build_overlap_sched_groups(). The latter one sets power and power_orig to SCHED_POWER_SCALE * cpumask_weight(sg_span) (since c3decf0dfbc95 'sched: Always initialize cpu-power' and 8e8339a3a1069 'sched: Initialize power_orig for overlapping groups'). So we could do the same in build_sched_groups(). IMHO, then the appropriate check 'if (!group->sgp->power_orig)' in sched_domain_debug_one() becomes superfluous. -- Dietmar Patch proposal against tip_sched_core. -- >8 -- Subject: [PATCH] sched: Initialize sg->sgp->power and sg->sgp->power_orig for non-overlapping groups --- kernel/sched/core.c | 17 +++-------------- 1 file changed, 3 insertions(+), 14 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9cae286824bb..ccf9b811ba37 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5206,18 +5206,6 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level, break; } - /* - * Even though we initialize ->power to something semi-sane, - * we leave power_orig unset. This allows us to detect if - * domain iteration is still funny without causing /0 traps. - */ - if (!group->sgp->power_orig) { - printk(KERN_CONT "\n"); - printk(KERN_ERR "ERROR: domain->cpu_power not " - "set\n"); - break; - } - if (!cpumask_weight(sched_group_cpus(group))) { printk(KERN_CONT "\n"); printk(KERN_ERR "ERROR: empty group\n"); @@ -5807,8 +5795,6 @@ build_sched_groups(struct sched_domain *sd, int cpu) continue; group = get_group(i, sdd, &sg); - cpumask_clear(sched_group_cpus(sg)); - sg->sgp->power = 0; cpumask_setall(sched_group_mask(sg)); for_each_cpu(j, span) { @@ -5819,6 +5805,9 @@ build_sched_groups(struct sched_domain *sd, int cpu) cpumask_set_cpu(j, sched_group_cpus(sg)); } + sg->sgp->power = SCHED_POWER_SCALE * cpumask_weight(sched_group_cpus(sg)); + sg->sgp->power_orig = sg->sgp->power; + if (!first) first = sg; if (last) -- 1.7.9.5