From: Mel Gorman <mgorman@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alex Thorlton <athorlton@sgi.com>, Rik van Riel <riel@redhat.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>, Mel Gorman <mgorman@suse.de>
Subject: [PATCH 14/18] mm: numa: Limit scope of lock for NUMA migrate rate limiting
Date: Mon, 9 Dec 2013 07:09:08 +0000 [thread overview]
Message-ID: <1386572952-1191-15-git-send-email-mgorman@suse.de> (raw)
In-Reply-To: <1386572952-1191-1-git-send-email-mgorman@suse.de>
NUMA migrate rate limiting protects a migration counter and window using
a lock but in some cases this can be a contended lock. It is not
critical that the number of pages be perfect, lost updates are
acceptable. Reduce the importance of this lock.
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
include/linux/mmzone.h | 5 +----
mm/migrate.c | 21 ++++++++++++---------
2 files changed, 13 insertions(+), 13 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index bd791e4..b835d3f 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -758,10 +758,7 @@ typedef struct pglist_data {
int kswapd_max_order;
enum zone_type classzone_idx;
#ifdef CONFIG_NUMA_BALANCING
- /*
- * Lock serializing the per destination node AutoNUMA memory
- * migration rate limiting data.
- */
+ /* Lock serializing the migrate rate limiting window */
spinlock_t numabalancing_migrate_lock;
/* Rate limiting time interval */
diff --git a/mm/migrate.c b/mm/migrate.c
index 77147bd..8b560d5 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1596,26 +1596,29 @@ bool migrate_ratelimited(int node)
static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
unsigned long nr_pages)
{
- bool rate_limited = false;
-
/*
* Rate-limit the amount of data that is being migrated to a node.
* Optimal placement is no good if the memory bus is saturated and
* all the time is being spent migrating!
*/
- spin_lock(&pgdat->numabalancing_migrate_lock);
if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
+ spin_lock(&pgdat->numabalancing_migrate_lock);
pgdat->numabalancing_migrate_nr_pages = 0;
pgdat->numabalancing_migrate_next_window = jiffies +
msecs_to_jiffies(migrate_interval_millisecs);
+ spin_unlock(&pgdat->numabalancing_migrate_lock);
}
if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
- rate_limited = true;
- else
- pgdat->numabalancing_migrate_nr_pages += nr_pages;
- spin_unlock(&pgdat->numabalancing_migrate_lock);
-
- return rate_limited;
+ return true;
+
+ /*
+ * This is an unlocked non-atomic update so errors are possible.
+ * The consequences are failing to migrate when we potentiall should
+ * have which is not severe enough to warrant locking. If it is ever
+ * a problem, it can be converted to a per-cpu counter.
+ */
+ pgdat->numabalancing_migrate_nr_pages += nr_pages;
+ return false;
}
static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
--
1.8.4
--
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next prev parent reply other threads:[~2013-12-09 7:09 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-09 7:08 [PATCH 00/18] NUMA balancing segmentation fault fixes and misc followups v3 Mel Gorman
2013-12-09 7:08 ` [PATCH 01/18] mm: numa: Serialise parallel get_user_page against THP migration Mel Gorman
2013-12-09 14:08 ` Rik van Riel
2013-12-09 7:08 ` [PATCH 02/18] mm: numa: Call MMU notifiers on " Mel Gorman
2013-12-09 14:09 ` Rik van Riel
2013-12-09 7:08 ` [PATCH 03/18] mm: Clear pmd_numa before invalidating Mel Gorman
2013-12-09 14:14 ` Rik van Riel
2013-12-09 7:08 ` [PATCH 04/18] mm: numa: Do not clear PMD during PTE update scan Mel Gorman
2013-12-09 14:22 ` Rik van Riel
2013-12-09 7:08 ` [PATCH 05/18] mm: numa: Do not clear PTE for pte_numa update Mel Gorman
2013-12-09 14:31 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 06/18] mm: numa: Ensure anon_vma is locked to prevent parallel THP splits Mel Gorman
2013-12-09 14:34 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 07/18] mm: numa: Avoid unnecessary work on the failure path Mel Gorman
2013-12-09 14:42 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 08/18] sched: numa: Skip inaccessible VMAs Mel Gorman
2013-12-09 14:50 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 09/18] mm: numa: Clear numa hinting information on mprotect Mel Gorman
2013-12-09 15:57 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 10/18] mm: numa: Avoid unnecessary disruption of NUMA hinting during migration Mel Gorman
2013-12-09 16:10 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 11/18] mm: fix TLB flush race between migration, and change_protection_range Mel Gorman
2013-12-10 14:25 ` Rik van Riel
2013-12-10 17:19 ` Mel Gorman
2013-12-10 18:02 ` Paul E. McKenney
2013-12-11 11:21 ` Mel Gorman
2013-12-09 7:09 ` [PATCH 12/18] mm: numa: Defer TLB flush for THP migration as long as possible Mel Gorman
2013-12-09 16:13 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 13/18] mm: numa: Make NUMA-migrate related functions static Mel Gorman
2013-12-09 7:20 ` Wanpeng Li
[not found] ` <20131209072010.GA3716@hacker.(null)>
2013-12-09 8:46 ` Mel Gorman
2013-12-09 8:57 ` Wanpeng Li
[not found] ` <20131209085720.GA16251@hacker.(null)>
2013-12-09 9:08 ` Mel Gorman
2013-12-09 9:13 ` Wanpeng Li
2013-12-09 16:14 ` Rik van Riel
2013-12-09 7:09 ` Mel Gorman [this message]
2013-12-09 16:47 ` [PATCH 14/18] mm: numa: Limit scope of lock for NUMA migrate rate limiting Rik van Riel
2013-12-09 7:09 ` [PATCH 15/18] mm: numa: Trace tasks that fail migration due to " Mel Gorman
2013-12-09 16:57 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 16/18] mm: numa: Do not automatically migrate KSM pages Mel Gorman
2013-12-09 16:57 ` Rik van Riel
2013-12-09 7:09 ` [PATCH 17/18] sched: Tracepoint task movement Mel Gorman
2013-12-09 18:54 ` Rik van Riel
2013-12-10 8:42 ` Mel Gorman
2013-12-10 9:06 ` Andrew Jones
2013-12-09 7:09 ` [PATCH 18/18] sched: Add tracepoints related to NUMA task migration Mel Gorman
2013-12-09 19:06 ` Rik van Riel
-- strict thread matches above, loose matches on Subject: below --
2013-12-10 15:51 [PATCH 00/17] NUMA balancing segmentation fault fixes and misc followups v4 Mel Gorman
2013-12-10 15:51 ` [PATCH 14/18] mm: numa: Limit scope of lock for NUMA migrate rate limiting Mel Gorman
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