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From: tip-bot for Rik van Riel <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, riel@redhat.com, hpa@zytor.com,
	mingo@kernel.org, torvalds@linux-foundation.org,
	peterz@infradead.org, tglx@linutronix.de
Subject: [tip:sched/core] sched/numa: Change scan period code to match intent
Date: Sat, 5 Jul 2014 03:45:44 -0700	[thread overview]
Message-ID: <tip-a22b4b012340b988dbe7a58461d6fcc582f34aa0@git.kernel.org> (raw)
In-Reply-To: <1403538095-31256-8-git-send-email-riel@redhat.com>

Commit-ID:  a22b4b012340b988dbe7a58461d6fcc582f34aa0
Gitweb:     http://git.kernel.org/tip/a22b4b012340b988dbe7a58461d6fcc582f34aa0
Author:     Rik van Riel <riel@redhat.com>
AuthorDate: Mon, 23 Jun 2014 11:41:35 -0400
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 5 Jul 2014 11:17:40 +0200

sched/numa: Change scan period code to match intent

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.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: mgorman@suse.de
Cc: chegu_vinod@hp.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1403538095-31256-8-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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 7bb2f46..a140c6a 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

  parent reply	other threads:[~2014-07-05 10:46 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-23 15:41 [PATCH 0/7] sched,numa: improve NUMA convergence times riel
2014-06-23 15:41 ` [PATCH 1/7] sched,numa: use group's max nid as task's preferred nid riel
2014-06-25 10:31   ` Mel Gorman
2014-07-05 10:44   ` [tip:sched/core] sched/numa: Use group's max nid as task' s " tip-bot for Rik van Riel
2014-06-23 15:41 ` [PATCH 3/7] sched,numa: use effective_load to balance NUMA loads riel
2014-06-23 15:41 ` [PATCH 4/7] sched,numa: simplify task_numa_compare riel
2014-06-25 10:39   ` Mel Gorman
2014-06-23 15:41 ` [PATCH 5/7] sched,numa: examine a task move when examining a task swap riel
2014-06-23 15:41 ` [PATCH 6/7] sched,numa: rework best node setting in task_numa_migrate riel
2014-07-05 10:45   ` [tip:sched/core] sched/numa: Rework best node setting in task_numa_migrate() tip-bot for Rik van Riel
2014-06-23 15:41 ` [PATCH 7/7] sched,numa: change scan period code to match intent riel
2014-06-25 10:19   ` Mel Gorman
2014-07-05 10:45   ` tip-bot for Rik van Riel [this message]
2014-06-23 22:30 ` [PATCH 8/7] sched,numa: do not let a move increase the imbalance Rik van Riel
2014-06-24 14:38   ` Peter Zijlstra
2014-06-24 15:30     ` Rik van Riel
2014-06-25  1:57     ` Rik van Riel
2014-06-24 19:14 ` [PATCH 9/7] sched,numa: remove task_h_load from task_numa_compare Rik van Riel
2014-06-25  5:07   ` Peter Zijlstra
2014-06-25  5:09     ` Rik van Riel
2014-06-25  5:21     ` Peter Zijlstra
2014-06-25  5:25       ` Rik van Riel
2014-06-25  5:31         ` Peter Zijlstra
2014-06-25  5:39           ` Rik van Riel
2014-06-25  5:57             ` Peter Zijlstra

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