[PATCH 25/54] mm/vmstat: replace cpumask_weight with cpumask_empty where appropriate

[PATCH 25/54] mm/vmstat: replace cpumask_weight with cpumask_empty where appropriate

[Yury Norov]

mm/vmstat.c code calls cpumask_weight() to check if any bit of a given
cpumask is set. We can do it more efficiently with cpumask_empty() because
cpumask_empty() stops traversing the cpumask as soon as it finds first set
bit, while cpumask_weight() counts all bits unconditionally.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 mm/vmstat.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 4057372745d0..f56f11e3eef5 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -2035,7 +2035,7 @@ static void __init init_cpu_node_state(void)
 	int node;
 
 	for_each_online_node(node) {
-		if (cpumask_weight(cpumask_of_node(node)) > 0)
+		if (!cpumask_empty(cpumask_of_node(node)))
 			node_set_state(node, N_CPU);
 	}
 }
@@ -2062,7 +2062,7 @@ static int vmstat_cpu_dead(unsigned int cpu)
 
 	refresh_zone_stat_thresholds();
 	node_cpus = cpumask_of_node(node);
-	if (cpumask_weight(node_cpus) > 0)
+	if (!cpumask_empty(node_cpus))
 		return 0;
 
 	node_clear_state(node, N_CPU);
-- 
2.30.2

[PATCH 51/54] mm: replace nodes_weight with nodes_weight_eq in mempolicy

[Yury Norov]

do_migrate_pages() calls nodes_weight() to compare the weight
of nodemask with a given number. We can do it more efficiently with
nodes_weight_eq() because conditional nodes_weight() may stop
traversing the nodemask earlier, as soon as condition is met.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 mm/mempolicy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index a86590b2507d..27817cf2f2a0 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1157,7 +1157,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
 			 *          [0-7] - > [3,4,5] moves only 0,1,2,6,7.
 			 */
 
-			if ((nodes_weight(*from) != nodes_weight(*to)) &&
+			if (!nodes_weight_eq(*from, nodes_weight(*to)) &&
 						(node_isset(s, *to)))
 				continue;
 
-- 
2.30.2

[PATCH 52/54] lib/nodemask: add num_node_state_eq()

[Yury Norov]

Kernel code uses num_node_state() to compare number of nodes with a given
number. The underlying code calls bitmap_weight(), and we can do it more
efficiently with num_node_state_eq because conditional nodes_weight may
stop traversing the nodemask earlier, as soon as condition is met.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 include/linux/nodemask.h | 5 +++++
 mm/page_alloc.c          | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index 197598e075e9..c5014dbf3cce 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -466,6 +466,11 @@ static inline int num_node_state(enum node_states state)
 	return nodes_weight(node_states[state]);
 }
 
+static inline int num_node_state_eq(enum node_states state, int num)
+{
+	return nodes_weight_eq(node_states[state], num);
+}
+
 #define for_each_node_state(__node, __state) \
 	for_each_node_mask((__node), node_states[__state])
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8dd6399bafb5..37496d764643 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8328,7 +8328,7 @@ void __init page_alloc_init(void)
 	int ret;
 
 #ifdef CONFIG_NUMA
-	if (num_node_state(N_MEMORY) == 1)
+	if (num_node_state_eq(N_MEMORY, 1))
 		hashdist = 0;
 #endif
 
-- 
2.30.2