From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932736AbeDXAj0 (ORCPT ); Mon, 23 Apr 2018 20:39:26 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:54680 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932691AbeDXAjA (ORCPT ); Mon, 23 Apr 2018 20:39:00 -0400 From: subhra mazumdar To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, mingo@redhat.com, daniel.lezcano@linaro.org, steven.sistare@oracle.com, dhaval.giani@oracle.com, rohit.k.jain@oracle.com, subhra.mazumdar@oracle.com Subject: [PATCH 3/3] sched: limit cpu search and rotate search window for scalability Date: Mon, 23 Apr 2018 17:41:16 -0700 Message-Id: <20180424004116.28151-4-subhra.mazumdar@oracle.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20180424004116.28151-1-subhra.mazumdar@oracle.com> References: <20180424004116.28151-1-subhra.mazumdar@oracle.com> X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8872 signatures=668698 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=978 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1804240003 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Lower the lower limit of idle cpu search in select_idle_cpu() and also put an upper limit. This helps in scalability of the search by restricting the search window. Also rotating the search window with help of next_cpu ensures any idle cpu is eventually found in case of high load. Signed-off-by: subhra mazumdar --- kernel/sched/fair.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d1d4769..62d585b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6279,7 +6279,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t u64 avg_cost, avg_idle; u64 time, cost; s64 delta; - int cpu, nr = INT_MAX; + int cpu, target_tmp, nr = INT_MAX; this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); if (!this_sd) @@ -6297,15 +6297,24 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t if (sched_feat(SIS_PROP)) { u64 span_avg = sd->span_weight * avg_idle; - if (span_avg > 4*avg_cost) + if (span_avg > 2*avg_cost) { nr = div_u64(span_avg, avg_cost); - else - nr = 4; + if (nr > 4) + nr = 4; + } else { + nr = 2; + } } + if (per_cpu(next_cpu, target) != -1) + target_tmp = per_cpu(next_cpu, target); + else + target_tmp = target; + time = local_clock(); - for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { + for_each_cpu_wrap(cpu, sched_domain_span(sd), target_tmp) { + per_cpu(next_cpu, target) = cpu; if (!--nr) return -1; if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) -- 2.9.3