From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754082Ab3I0N3M (ORCPT ); Fri, 27 Sep 2013 09:29:12 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55994 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753814Ab3I0N2v (ORCPT ); Fri, 27 Sep 2013 09:28:51 -0400 From: Mel Gorman To: Peter Zijlstra , Rik van Riel Cc: Srikar Dronamraju , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML , Mel Gorman Subject: [PATCH 63/63] sched: numa: periodically retry task_numa_migrate Date: Fri, 27 Sep 2013 14:27:48 +0100 Message-Id: <1380288468-5551-64-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1380288468-5551-1-git-send-email-mgorman@suse.de> References: <1380288468-5551-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rik van Riel Short spikes of CPU load can lead to a task being migrated away from its preferred node for temporary reasons. It is important that the task is migrated back to where it belongs, in order to avoid migrating too much memory to its new location, and generally disturbing a task's NUMA location. This patch fixes NUMA placement for 4 specjbb instances on a 4 node system. Without this patch, things take longer to converge, and processes are not always completely on their own node. Signed-off-by: Rik van Riel Signed-off-by: Mel Gorman --- kernel/sched/fair.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fced601..8fe5789 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1259,18 +1259,19 @@ static int task_numa_migrate(struct task_struct *p) /* Attempt to migrate a task to a CPU on the preferred node. */ static void numa_migrate_preferred(struct task_struct *p) { - /* Success if task is already running on preferred CPU */ - p->numa_migrate_retry = 0; - if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid) + /* This task has no NUMA fault statistics yet */ + if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults)) return; - /* This task has no NUMA fault statistics yet */ - if (unlikely(p->numa_preferred_nid == -1)) + /* Periodically retry migrating the task to the preferred node */ + p->numa_migrate_retry = jiffies + HZ; + + /* Success if task is already running on preferred CPU */ + if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid) return; /* Otherwise, try migrate to a CPU on the preferred node */ - if (task_numa_migrate(p) != 0) - p->numa_migrate_retry = jiffies + HZ*5; + task_numa_migrate(p); } /* @@ -1629,8 +1630,11 @@ void task_numa_fault(int last_cpupid, int node, int pages, int flags) task_numa_placement(p); - /* Retry task to preferred node migration if it previously failed */ - if (p->numa_migrate_retry && time_after(jiffies, p->numa_migrate_retry)) + /* + * Retry task to preferred node migration periodically, in case it + * case it previously failed, or the scheduler moved us. + */ + if (time_after(jiffies, p->numa_migrate_retry)) numa_migrate_preferred(p); if (migrated) -- 1.8.1.4