[PATCH 14/18] 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: Mel Gorman
Reviewed-by: Rik van Riel
---
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 b6eef65..564d5c9 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(>numabalancing_migrate_lock);
if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
+ spin_lock(>numabalancing_migrate_lock);
pgdat->numabalancing_migrate_nr_pages = 0;
pgdat->numabalancing_migrate_next_window = jiffies +
msecs_to_jiffies(migrate_interval_millisecs);
+ spin_unlock(>numabalancing_migrate_lock);
}
if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
- rate_limited = true;
- else
- pgdat->numabalancing_migrate_nr_pages += nr_pages;
- spin_unlock(>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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[PATCH 14/18] 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: Mel Gorman mgor...@suse.de
Reviewed-by: Rik van Riel r...@redhat.com
---
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 b6eef65..564d5c9 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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Re: [PATCH 14/18] mm: numa: Limit scope of lock for NUMA migrate rate limiting
On 12/09/2013 02:09 AM, Mel Gorman wrote: > 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 Reviewed-by: Rik van Riel -- All rights reversed -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 14/18] mm: numa: Limit scope of lock for NUMA migrate rate limiting
On 12/09/2013 02:09 AM, Mel Gorman wrote: 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 mgor...@suse.de Reviewed-by: Rik van Riel r...@redhat.com -- All rights reversed -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 14/18] 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: Mel Gorman
---
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(>numabalancing_migrate_lock);
if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
+ spin_lock(>numabalancing_migrate_lock);
pgdat->numabalancing_migrate_nr_pages = 0;
pgdat->numabalancing_migrate_next_window = jiffies +
msecs_to_jiffies(migrate_interval_millisecs);
+ spin_unlock(>numabalancing_migrate_lock);
}
if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
- rate_limited = true;
- else
- pgdat->numabalancing_migrate_nr_pages += nr_pages;
- spin_unlock(>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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Please read the FAQ at http://www.tux.org/lkml/
[PATCH 14/18] 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: Mel Gorman mgor...@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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the body of a message to majord...@vger.kernel.org
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