mm/list_lru: optimize condition of exiting the loop

PATCH Superseded Hui Su 2 participants 3 messages Oct 27, 2020

Subsystems (2)

Memory management Shrinker

lore

Share & tools

lore

Hui Su

author

2020-10-27 17:05 UTC #0 lore raw

PATCH 1/1 mm/list_lru: optimize condition of exiting the loop

In list_lru_walk(), nr_to_walk type is 'unsigned long', so nr_to_walk won't be '< 0'.

In list_lru_walk_node(), nr_to_walk type is 'unsigned long', so *nr_to_walk won't be '< 0' too.

We can use '!nr_to_walk' instead of 'nr_to_walk <= 0', which is more precise.

Signed-off-by Hui Su <[email protected]>

---
 include/linux/list_lru.h | 2 +-
 mm/list_lru.c            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

include/linux/list_lru.h +1 -1

index 9dcaa3e582c9..b7bc4a2636b9 100644
@@ -214,7 +214,7 @@ list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
 	for_each_node_state(nid, N_NORMAL_MEMORY) {
 		isolated += list_lru_walk_node(lru, nid, isolate,
 					       cb_arg, &nr_to_walk);
-		if (nr_to_walk <= 0)
+		if (!nr_to_walk)
 			break;
 	}
 	return isolated;

mm/list_lru.c +1 -1

index 5aa6e44bc2ae..39b8d467159d 100644
@@ -304,7 +304,7 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 							nr_to_walk);
 			spin_unlock(&nlru->lock);
 
-			if (*nr_to_walk <= 0)
+			if (!*nr_to_walk)
 				break;
 		}
 	}

Signature · 1 line

2.25.1

Vlastimil Babka

2020-10-27 18:45 UTC #1 lore raw

Quoted 10 lines · Hui Su

In list_lru_walk(), nr_to_walk type is 'unsigned long', so nr_to_walk won't be '< 0'.
In list_lru_walk_node(), nr_to_walk type is 'unsigned long', so *nr_to_walk won't be '< 0' too.
We can use '!nr_to_walk' instead of 'nr_to_walk <= 0', which is more precise.
Signed-off-by Hui Su <[email protected]>

OK. Why not this too?

mm/list_lru.c +1 -1

@@ -294,7 +294,7 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 
        isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
                                      nr_to_walk);
-       if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
+       if (*nr_to_walk && list_lru_memcg_aware(lru)) {
                for_each_memcg_cache_index(memcg_idx) {
                        struct list_lru_node *nlru = &lru->node[nid];

Quoted 32 lines

---
  include/linux/list_lru.h | 2 +-
  mm/list_lru.c            | 2 +-
  2 files changed, 2 insertions(+), 2 deletions(-)

include/linux/list_lru.h +1 -1

index 9dcaa3e582c9..b7bc4a2636b9 100644
@@ -214,7 +214,7 @@ list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
  	for_each_node_state(nid, N_NORMAL_MEMORY) {
  		isolated += list_lru_walk_node(lru, nid, isolate,
  					       cb_arg, &nr_to_walk);
-		if (nr_to_walk <= 0)
+		if (!nr_to_walk)
  			break;
  	}
  	return isolated;

mm/list_lru.c +1 -1

index 5aa6e44bc2ae..39b8d467159d 100644
@@ -304,7 +304,7 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
  							nr_to_walk);
  			spin_unlock(&nlru->lock);
 
-			if (*nr_to_walk <= 0)
+			if (!*nr_to_walk)
  				break;
  		}
  	}

Hui Su

author

2020-10-27 19:07 UTC #2 lore raw

Quoted 18 lines · Vlastimil Babka

Quoted 10 lines · Hui Su
In list_lru_walk(), nr_to_walk type is 'unsigned long', so nr_to_walk won't be '< 0'.
In list_lru_walk_node(), nr_to_walk type is 'unsigned long', so *nr_to_walk won't be '< 0' too.
We can use '!nr_to_walk' instead of 'nr_to_walk <= 0', which is more precise.
Signed-off-by Hui Su <[email protected]>
OK. Why not this too?

mm/list_lru.c unsigned long list_lru_walk_node(struct list_lru *lru, int nid, · line 300

Quoted 8 lines

mm/list_lru.c +1 -1

@@ -294,7 +294,7 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 
        isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
                                      nr_to_walk);
-       if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
+       if (*nr_to_walk && list_lru_memcg_aware(lru)) {
                for_each_memcg_cache_index(memcg_idx) {
                        struct list_lru_node *nlru = &lru->node[nid];

Thanks for your fast reply.

I did not notice that, and i would add this to my change. I will resend PATCH V2, and cc to you.

Thanks.