Subject: [PATCH] hugetlb: vmstat events for huge page allocations

Allocating huge pages directly from the buddy allocator is not guaranteed to
succeed.  Success depends on several factors (such as the amount of physical
memory available and the level of fragmentation).  With the addition of
dynamic hugetlb pool resizing, allocations can occur much more frequently.
For these reasons it is desirable to keep track of huge page allocation
successes and failures.

Add two new vmstat entries to track huge page allocations that succeed and
fail.  The presence of the two entries is contingent upon CONFIG_HUGETLB_PAGE
being enabled.

[[email protected]: reduced ifdeffery]
Signed-off-by: Adam Litke <[email protected]>
Signed-off-by: Eric Munson <[email protected]>
Tested-by: Mel Gorman <[email protected]>
Reviewed-by: Andy Whitcroft <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/vmstat.h

@@ -25,6 +25,7 @@
 #define HIGHMEM_ZONE(xx)
 #endif
 
+
 #define FOR_ALL_ZONES(xx) DMA_ZONE(xx) DMA32_ZONE(xx) xx##_NORMAL HIGHMEM_ZONE(xx) , xx##_MOVABLE
 
 enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
@@ -37,6 +38,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		FOR_ALL_ZONES(PGSCAN_DIRECT),
 		PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL,
 		PAGEOUTRUN, ALLOCSTALL, PGROTATED,
+#ifdef CONFIG_HUGETLB_PAGE
+		HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL,
+#endif
 		NR_VM_EVENT_ITEMS
 };
 

mm/hugetlb.c

@@ -242,6 +242,11 @@ static int alloc_fresh_huge_page(void)
 		hugetlb_next_nid = next_nid;
 	} while (!page && hugetlb_next_nid != start_nid);
 
+	if (ret)
+		count_vm_event(HTLB_BUDDY_PGALLOC);
+	else
+		count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
+
 	return ret;
 }
 
@@ -302,9 +307,11 @@ static struct page *alloc_buddy_huge_page(struct vm_area_struct *vma,
 		 */
 		nr_huge_pages_node[nid]++;
 		surplus_huge_pages_node[nid]++;
+		__count_vm_event(HTLB_BUDDY_PGALLOC);
 	} else {
 		nr_huge_pages--;
 		surplus_huge_pages--;
+		__count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
 	}
 	spin_unlock(&hugetlb_lock);
 

mm/vmstat.c

@@ -645,6 +645,10 @@ static const char * const vmstat_text[] = {
 	"allocstall",
 
 	"pgrotated",
+#ifdef CONFIG_HUGETLB_PAGE
+	"htlb_buddy_alloc_success",
+	"htlb_buddy_alloc_fail",
+#endif
 #endif
 };