[RFC PATCH 3/4] x86/mm/cpa: add merge event counter

[Aaron Lu]

Like split event counter, this patch add counter for merge event.

Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
---
 arch/x86/mm/pat/set_memory.c  | 19 +++++++++++++++++++
 include/linux/vm_event_item.h |  2 ++
 mm/vmstat.c                   |  2 ++
 3 files changed, 23 insertions(+)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index fea2c70ff37f..1be9aab42c79 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -105,6 +105,23 @@ static void split_page_count(int level)
 	direct_pages_count[level - 1] += PTRS_PER_PTE;
 }
 
+static void merge_page_count(int level)
+{
+	if (direct_pages_count[level] < PTRS_PER_PTE) {
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	direct_pages_count[level] -= PTRS_PER_PTE;
+	if (system_state == SYSTEM_RUNNING) {
+		if (level == PG_LEVEL_4K)
+			count_vm_event(DIRECT_MAP_LEVEL1_MERGE);
+		else if (level == PG_LEVEL_2M)
+			count_vm_event(DIRECT_MAP_LEVEL2_MERGE);
+	}
+	direct_pages_count[level + 1]++;
+}
+
 void arch_report_meminfo(struct seq_file *m)
 {
 	seq_printf(m, "DirectMap4k:    %8lu kB\n",
@@ -875,6 +892,8 @@ static void merge_splitted_mapping(struct page *pgt, int level)
 
 	__ClearPageSplitpgt(pgt);
 	__free_page(pgt);
+
+	merge_page_count(level);
 }
 
 static pgprot_t pgprot_clear_protnone_bits(pgprot_t prot)
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 404024486fa5..00a9a435af49 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -143,6 +143,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 #ifdef CONFIG_X86
 		DIRECT_MAP_LEVEL2_SPLIT,
 		DIRECT_MAP_LEVEL3_SPLIT,
+		DIRECT_MAP_LEVEL1_MERGE,
+		DIRECT_MAP_LEVEL2_MERGE,
 #endif
 		NR_VM_EVENT_ITEMS
 };
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 373d2730fcf2..1a4287a4d614 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1403,6 +1403,8 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_X86
 	"direct_map_level2_splits",
 	"direct_map_level3_splits",
+	"direct_map_level1_merges",
+	"direct_map_level2_merges",
 #endif
 #endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
 };
-- 
2.37.1