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Commit 1c5e9c27 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
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mm: numa: limit scope of lock for NUMA migrate rate limiting 



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: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1c30e017

include/linux/mmzone.h

+1 −4
Original line number Diff line number Diff line
@@ -764,10 +764,7 @@ 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 */

mm/migrate.c

+12 −9
Original line number Diff line number Diff line
@@ -1602,26 +1602,29 @@ 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 true;



	return rate_limited;

	/*

	 * 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)