@@ -709,6 +709,29 @@ nr_anon_partially_mapped
        an anonymous THP as "partially mapped" and count it here, even though it
        is not actually partially mapped anymore.
 
+collapse_exceed_none_pte
+       The number of anonymous mTHP pte ranges where the number of none PTEs
+       exceeded the max_ptes_none threshold. For mTHP collapse, khugepaged
+       checks a PMD region and tracks which PTEs are present. It then tries
+       to collapse to the largest enabled mTHP size. The allowed number of empty
+       PTEs is the max_ptes_none threshold scaled by the collapse order. This
+       counter records the number of times a collapse attempt was skipped for
+       this reason, and khugepaged moved on to try the next available mTHP size.
+
+collapse_exceed_swap_pte
+       The number of anonymous mTHP pte ranges which contain at least one swap
+       PTE. Currently khugepaged does not support collapsing mTHP regions
+       that contain a swap PTE. This counter can be used to monitor the
+       number of khugepaged mTHP collapses that failed due to the presence
+       of a swap PTE.
+
+collapse_exceed_shared_pte
+       The number of anonymous mTHP pte ranges which contain at least one shared
+       PTE. Currently khugepaged does not support collapsing mTHP pte ranges
+       that contain a shared PTE. This counter can be used to monitor the
+       number of khugepaged mTHP collapses that failed due to the presence
+       of a shared PTE.
+
 As the system ages, allocating huge pages may be expensive as the
 system uses memory compaction to copy data around memory to free a
 huge page for use. There are some counters in ``/proc/vmstat`` to help

@@ -144,6 +144,9 @@ enum mthp_stat_item {
 	MTHP_STAT_SPLIT_DEFERRED,
 	MTHP_STAT_NR_ANON,
 	MTHP_STAT_NR_ANON_PARTIALLY_MAPPED,
+	MTHP_STAT_COLLAPSE_EXCEED_SWAP,
+	MTHP_STAT_COLLAPSE_EXCEED_NONE,
+	MTHP_STAT_COLLAPSE_EXCEED_SHARED,
 	__MTHP_STAT_COUNT
 };
 

@@ -638,6 +638,10 @@ DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED);
 DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED);
 DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON);
 DEFINE_MTHP_STAT_ATTR(nr_anon_partially_mapped, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_swap_pte, MTHP_STAT_COLLAPSE_EXCEED_SWAP);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_none_pte, MTHP_STAT_COLLAPSE_EXCEED_NONE);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_shared_pte, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
+
 
 static struct attribute *anon_stats_attrs[] = {
 	&anon_fault_alloc_attr.attr,

@@ -654,6 +658,9 @@ static struct attribute *anon_stats_attrs[] = {
 	&split_deferred_attr.attr,
 	&nr_anon_attr.attr,
 	&nr_anon_partially_mapped_attr.attr,
+	&collapse_exceed_swap_pte_attr.attr,
+	&collapse_exceed_none_pte_attr.attr,
+	&collapse_exceed_shared_pte_attr.attr,
 	NULL,
 };
 

@@ -589,7 +589,9 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 				continue;
 			} else {
 				result = SCAN_EXCEED_NONE_PTE;
-				count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
+				if (order == HPAGE_PMD_ORDER)
+					count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
+				count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_NONE);
 				goto out;
 			}
 		}

@@ -628,10 +630,17 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 			 * shared may cause a future higher order collapse on a
 			 * rescan of the same range.
 			 */
-			if (order != HPAGE_PMD_ORDER || (cc->is_khugepaged &&
-			    shared > khugepaged_max_ptes_shared)) {
+			if (order != HPAGE_PMD_ORDER) {
+				result = SCAN_EXCEED_SHARED_PTE;
+				count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
+				goto out;
+			}
+
+			if (cc->is_khugepaged &&
+			    shared > khugepaged_max_ptes_shared) {
 				result = SCAN_EXCEED_SHARED_PTE;
 				count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
+				count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
 				goto out;
 			}
 		}

@@ -1071,6 +1080,7 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
 		 * range.
 		 */
 		if (order != HPAGE_PMD_ORDER) {
+			count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SWAP);
 			pte_unmap(pte);
 			mmap_read_unlock(mm);
 			result = SCAN_EXCEED_SWAP_PTE;