[PATCH, RFC 05/10] mm, vmstats: new THP splitting event

[Kirill A. Shutemov]

The patch replaces THP_SPLIT with tree events: THP_SPLIT_PAGE,
THP_SPLIT_PAGE_FAILT and THP_SPLIT_PMD. It reflects the fact that we
now can split PMD without the compound page and that split_huge_page()
can fail.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 include/linux/vm_event_item.h | 4 +++-
 mm/huge_memory.c              | 2 ++
 mm/vmstat.c                   | 4 +++-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index ced92345c963..b44dffa769b9 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -68,7 +68,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		THP_FAULT_FALLBACK,
 		THP_COLLAPSE_ALLOC,
 		THP_COLLAPSE_ALLOC_FAILED,
-		THP_SPLIT,
+		THP_SPLIT_PAGE,
+		THP_SPLIT_PAGE_FAILED,
+		THP_SPLIT_PMD,
 		THP_ZERO_PAGE_ALLOC,
 		THP_ZERO_PAGE_ALLOC_FAILED,
 #endif
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 752c850f6941..fec89aedcedd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1578,6 +1578,7 @@ unlock:
 
 int split_huge_page_to_list(struct page *page, struct list_head *list)
 {
+	count_vm_event(THP_SPLIT_PAGE_FAILED);
 	return -EBUSY;
 }
 
@@ -2496,6 +2497,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 		return;
 	}
+	count_vm_event(THP_SPLIT_PMD);
 	if (is_huge_zero_pmd(*pmd)) {
 		__split_huge_zero_page_pmd(vma, haddr, pmd);
 		spin_unlock(ptl);
diff --git a/mm/vmstat.c b/mm/vmstat.c
index b37bd49bfd55..6a155f0476e8 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -855,7 +855,9 @@ const char * const vmstat_text[] = {
 	"thp_fault_fallback",
 	"thp_collapse_alloc",
 	"thp_collapse_alloc_failed",
-	"thp_split",
+	"thp_split_page",
+	"thp_split_page_failed",
+	"thp_split_pmd",
 	"thp_zero_page_alloc",
 	"thp_zero_page_alloc_failed",
 #endif
-- 
2.0.0.rc4

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