[RFC 2/3] virtio_balloon: introduce memory allocation stall counter

[zhenwei pi]

Memory allocation stall counter represents the performance/latency of
memory allocation, expose this counter to the host side by virtio
balloon device via out-of-bound way.

Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
---
 drivers/virtio/virtio_balloon.c     | 19 ++++++++++++++++++-
 include/uapi/linux/virtio_balloon.h |  6 ++++--
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index fd8daa742734..4b9c9569f6e5 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -321,7 +321,7 @@ static unsigned int update_balloon_stats(struct virtio_balloon *vb)
 	unsigned long events[NR_VM_EVENT_ITEMS];
 	struct sysinfo i;
 	unsigned int idx = 0;
-	long available;
+	long available, stall = 0;
 	unsigned long caches;
 
 	all_vm_events(events);
@@ -355,6 +355,23 @@ static unsigned int update_balloon_stats(struct virtio_balloon *vb)
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_OOM_KILL,
 				events[OOM_KILL]);
 
+	/* sum all the stall event */
+#ifdef CONFIG_ZONE_DMA
+	stall += events[ALLOCSTALL_DMA];
+#endif
+#ifdef CONFIG_ZONE_DMA32
+	stall += events[ALLOCSTALL_DMA32];
+#endif
+#ifdef CONFIG_HIGHMEM
+	stall += events[ALLOCSTALL_HIGH];
+#endif
+#ifdef CONFIG_ZONE_DEVICE
+	stall += events[ALLOCSTALL_DEVICE];
+#endif
+	stall += events[ALLOCSTALL_NORMAL];
+	stall += events[ALLOCSTALL_MOVABLE];
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_ALLOC_STALL, stall);
+
 	return idx;
 }
 
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index cde5547e64a7..13d0c32ba27c 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -72,7 +72,8 @@ struct virtio_balloon_config {
 #define VIRTIO_BALLOON_S_HTLB_PGALLOC  8  /* Hugetlb page allocations */
 #define VIRTIO_BALLOON_S_HTLB_PGFAIL   9  /* Hugetlb page allocation failures */
 #define VIRTIO_BALLOON_S_OOM_KILL      10 /* OOM killer invocations */
-#define VIRTIO_BALLOON_S_NR       11
+#define VIRTIO_BALLOON_S_ALLOC_STALL   11 /* Stall count of memory allocatoin */
+#define VIRTIO_BALLOON_S_NR       12
 
 #define VIRTIO_BALLOON_S_NAMES_WITH_PREFIX(VIRTIO_BALLOON_S_NAMES_prefix) { \
 	VIRTIO_BALLOON_S_NAMES_prefix "swap-in", \
@@ -85,7 +86,8 @@ struct virtio_balloon_config {
 	VIRTIO_BALLOON_S_NAMES_prefix "disk-caches", \
 	VIRTIO_BALLOON_S_NAMES_prefix "hugetlb-allocations", \
 	VIRTIO_BALLOON_S_NAMES_prefix "hugetlb-failures", \
-	VIRTIO_BALLOON_S_NAMES_prefix "oom-kill" \
+	VIRTIO_BALLOON_S_NAMES_prefix "oom-kill", \
+	VIRTIO_BALLOON_S_NAMES_prefix "alloc-stall" \
 }
 
 #define VIRTIO_BALLOON_S_NAMES VIRTIO_BALLOON_S_NAMES_WITH_PREFIX("")
-- 
2.34.1