From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932329AbaFWPt3 (ORCPT ); Mon, 23 Jun 2014 11:49:29 -0400 Received: from shelob.surriel.com ([74.92.59.67]:54947 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932306AbaFWPt1 (ORCPT ); Mon, 23 Jun 2014 11:49:27 -0400 From: riel@redhat.com To: linux-kernel@vger.kernel.org Cc: chegu_vinod@hp.com, peterz@infradead.com, mgorman@suse.de, mingo@kernel.org Subject: [PATCH 7/7] sched,numa: change scan period code to match intent Date: Mon, 23 Jun 2014 11:41:35 -0400 Message-Id: <1403538095-31256-8-git-send-email-riel@redhat.com> X-Mailer: git-send-email 1.8.5.3 In-Reply-To: <1403538095-31256-1-git-send-email-riel@redhat.com> References: <1403538095-31256-1-git-send-email-riel@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rik van Riel Reading through the scan period code and comment, it appears the intent was to slow down NUMA scanning when a majority of accesses are on the local node, specifically a local:remote ratio of 3:1. However, the code actually tests local / (local + remote), and the actual cut-off point was around 30% local accesses, well before a task has actually converged on a node. Changing the threshold to 7 means scanning slows down when a task has around 70% of its accesses local, which appears to match the intent of the code more closely. Cc: Mel Gorman Signed-off-by: Rik van Riel --- kernel/sched/fair.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ee35576..1aaa3b4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1452,12 +1452,12 @@ static void update_numa_active_node_mask(struct numa_group *numa_group) /* * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS * increments. The more local the fault statistics are, the higher the scan - * period will be for the next scan window. If local/remote ratio is below - * NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the - * scan period will decrease + * period will be for the next scan window. If local/(local+remote) ratio is + * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) + * the scan period will decrease. Aim for 70% local accesses. */ #define NUMA_PERIOD_SLOTS 10 -#define NUMA_PERIOD_THRESHOLD 3 +#define NUMA_PERIOD_THRESHOLD 7 /* * Increase the scan period (slow down scanning) if the majority of -- 1.8.5.3