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mm: numa: limit scope of lock for NUMA migrate rate limiting

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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 <[email protected]>
Reviewed-by: Rik van Riel <[email protected]>
Cc: Alex Thorlton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Mel Gorman 2014-01-21 15:50:59 -08:00 • committed by Linus Torvalds
commit 1c5e9c27cb
2 changed files with 13 additions and 13 deletions
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21
mm/migrate.c
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@ -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 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)