Re: [PATCH 2/3] mm/compaction: add and use for_each_populated_zone_pgdat() helper

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On 2024/3/15 13:38, Luis Chamberlain wrote:
On Thu, Mar 14, 2024 at 03:19:45PM +0800, Baolin Wang wrote:


On 2024/3/14 08:54, Luis Chamberlain wrote:
We can just wrap most of the work done on fragmentation_score_node()
into a pgdat helper for populated zones. Add the helper and use it.

Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
---
   include/linux/mmzone.h | 8 ++++++++
   mm/compaction.c        | 9 ++-------
   2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a497f189d988..1fd74c7100ec 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1597,6 +1597,14 @@ extern struct zone *next_zone(struct zone *zone);
   			; /* do nothing */		\
   		else
+#define for_each_populated_zone_pgdat(zone, pgdat)	\
+	for (zone = pgdat->node_zones;			\
+	     zone;					\
+	     zone = next_zone(zone))			\
+		if (!populated_zone(zone))		\
+			; /* do nothing */		\
+		else

I think this will break the original logics, since the next_zone() will
iterate over all memory zones, instead of only the memory zones of the
specified node.

Definitely, thanks, so we'd need something like this in addition:

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 34b729fc751b..bd11d33ea14d 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1568,6 +1568,7 @@ static inline struct pglist_data *NODE_DATA(int nid)
  extern struct pglist_data *first_online_pgdat(void);
  extern struct pglist_data *next_online_pgdat(struct pglist_data *pgdat);
  extern struct zone *next_zone(struct zone *zone);
+extern struct zone *next_zone_pgdat(struct zone *zone, struct pglist_data *pgdat);
/**
   * for_each_online_pgdat - helper macro to iterate over all online nodes
@@ -1600,7 +1601,7 @@ extern struct zone *next_zone(struct zone *zone);
  #define for_each_populated_zone_pgdat(zone, pgdat)	\
  	for (zone = pgdat->node_zones;			\
  	     zone;					\
-	     zone = next_zone(zone))			\
+	     zone = next_zone_pgdat(zone, pgdat))	\
  		if (!populated_zone(zone))		\
  			; /* do nothing */		\
  		else
diff --git a/mm/compaction.c b/mm/compaction.c
index 015126803017..96434f6fc1ad 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2152,7 +2152,6 @@ static unsigned int fragmentation_score_node(pg_data_t *pgdat)
  {
  	unsigned int score = 0;
  	struct zone *zone;
-	int zoneid;
for_each_populated_zone_pgdat(zone, pgdat)
  		score += fragmentation_score_zone_weighted(zone);
diff --git a/mm/mmzone.c b/mm/mmzone.c
index c01896eca736..043a6dc16c05 100644
--- a/mm/mmzone.c
+++ b/mm/mmzone.c
@@ -43,6 +43,18 @@ struct zone *next_zone(struct zone *zone)
  	return zone;
  }
+/*
+ * next_zone_pgdat - helper magic for for_each_zone() per node
+ */
+struct zone *next_zone_pgdat(struct zone *zone, struct pglist_data *pgdat)
+{
+	if (!zone || !pgdat)
+		return NULL;

Seems unnecessary, you already accessed them before calling next_zone_pgdat(). Otherwise, looks good to me.

+	if (zone < pgdat->node_zones + MAX_NR_ZONES - 1)
+		return ++zone;
+	return NULL;
+}
+
  static inline int zref_in_nodemask(struct zoneref *zref, nodemask_t *nodes)
  {
  #ifdef CONFIG_NUMA




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