virtio: Add memory statistics reporting to the balloon driver (V4)

Changes since V3: - Do not do endian conversions as they will be done in the host - Report stats that reference a quantity of memory in bytes - Minor coding style updates Changes since V2: - Increase stat field size to 64 bits - Report all sizes in kb (not pages) - Drop anon_pages stat and fix endianness conversion Changes since V1: - Use a virtqueue instead of the device config space When using ballooning to manage overcommitted memory on a host, a system for guests to communicate their memory usage to the host can provide information that will minimize the impact of ballooning on the guests. The current method employs a daemon running in each guest that communicates memory statistics to a host daemon at a specified time interval. The host daemon aggregates this information and inflates and/or deflates balloons according to the level of host memory pressure. This approach is effective but overly complex since a daemon must be installed inside each guest and coordinated to communicate with the host. A simpler approach is to collect memory statistics in the virtio balloon driver and communicate them directly to the hypervisor. This patch enables the guest-side support by adding stats collection and reporting to the virtio balloon driver. Signed-off-by: Adam Litke <agl@us.ibm.com> Cc: Anthony Liguori <anthony@codemonkey.ws> Cc: virtualization@lists.linux-foundation.org Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor fixes)

virtio: Add memory statistics reporting to the balloon driver (V4)
Changes since V3: - Do not do endian conversions as they will be done in the host - Report stats that reference a quantity of memory in bytes - Minor coding style updates Changes since V2: - Increase stat field size to 64 bits - Report all sizes in kb (not pages) - Drop anon_pages stat and fix endianness conversion Changes since V1: - Use a virtqueue instead of the device config space When using ballooning to manage overcommitted memory on a host, a system for guests to communicate their memory usage to the host can provide information that will minimize the impact of ballooning on the guests. The current method employs a daemon running in each guest that communicates memory statistics to a host daemon at a specified time interval. The host daemon aggregates this information and inflates and/or deflates balloons according to the level of host memory pressure. This approach is effective but overly complex since a daemon must be installed inside each guest and coordinated to communicate with the host. A simpler approach is to collect memory statistics in the virtio balloon driver and communicate them directly to the hypervisor. This patch enables the guest-side support by adding stats collection and reporting to the virtio balloon driver. Signed-off-by: Adam Litke <agl@us.ibm.com> Cc: Anthony Liguori <anthony@codemonkey.ws> Cc: virtualization@lists.linux-foundation.org Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor fixes)
Adam Litke · Rusty Russell
1 parent 1f08b833dd
Showing 2 changed files with 101 additions and 8 deletions Side-by-side Diff
drivers/virtio/virtio_balloon.c
include/linux/virtio_balloon.h
@@ -28,7 +28,7 @@
 struct virtio_balloon
 {
 	struct virtio_device *vdev;
-	struct virtqueue *inflate_vq, *deflate_vq;
+	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
  
 	/* Where the ballooning thread waits for config to change. */
 	wait_queue_head_t config_change;
@@ -49,6 +49,9 @@
 	/* The array of pfns we tell the Host about. */
 	unsigned int num_pfns;
 	u32 pfns[256];
+
+	/* Memory statistics */
+	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 };
  
 static struct virtio_device_id id_table[] = {
@@ -154,6 +157,62 @@
 	}
 }
  
+static inline void update_stat(struct virtio_balloon *vb, int idx,
+			       u16 tag, u64 val)
+{
+	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
+	vb->stats[idx].tag = tag;
+	vb->stats[idx].val = val;
+}
+
+#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
+
+static void update_balloon_stats(struct virtio_balloon *vb)
+{
+	unsigned long events[NR_VM_EVENT_ITEMS];
+	struct sysinfo i;
+	int idx = 0;
+
+	all_vm_events(events);
+	si_meminfo(&i);
+
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
+				pages_to_bytes(events[PSWPIN]));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
+				pages_to_bytes(events[PSWPOUT]));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
+				pages_to_bytes(i.freeram));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
+				pages_to_bytes(i.totalram));
+}
+
+/*
+ * While most virtqueues communicate guest-initiated requests to the hypervisor,
+ * the stats queue operates in reverse.  The driver initializes the virtqueue
+ * with a single buffer.  From that point forward, all conversations consist of
+ * a hypervisor request (a call to this function) which directs us to refill
+ * the virtqueue with a fresh stats buffer.
+ */
+static void stats_ack(struct virtqueue *vq)
+{
+	struct virtio_balloon *vb;
+	unsigned int len;
+	struct scatterlist sg;
+
+	vb = vq->vq_ops->get_buf(vq, &len);
+	if (!vb)
+		return;
+
+	update_balloon_stats(vb);
+
+	sg_init_one(&sg, vb->stats, sizeof(vb->stats));
+	if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
+		BUG();
+	vq->vq_ops->kick(vq);
+}
+
 static void virtballoon_changed(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;
@@ -204,10 +263,10 @@
 static int virtballoon_probe(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb;
-	struct virtqueue *vqs[2];
-	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack };
-	const char *names[] = { "inflate", "deflate" };
-	int err;
+	struct virtqueue *vqs[3];
+	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_ack };
+	const char *names[] = { "inflate", "deflate", "stats" };
+	int err, nvqs;
  
 	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
 	if (!vb) {
  
  
@@ -220,14 +279,30 @@
 	init_waitqueue_head(&vb->config_change);
 	vb->vdev = vdev;
  
-	/* We expect two virtqueues. */
-	err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
+	/* We expect two virtqueues: inflate and deflate,
+	 * and optionally stat. */
+	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
+	err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
 	if (err)
 		goto out_free_vb;
  
 	vb->inflate_vq = vqs[0];
 	vb->deflate_vq = vqs[1];
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
+		struct scatterlist sg;
+		vb->stats_vq = vqs[2];
  
+		/*
+		 * Prime this virtqueue with one buffer so the hypervisor can
+		 * use it to signal us later.
+		 */
+		sg_init_one(&sg, vb->stats, sizeof vb->stats);
+		if (vb->stats_vq->vq_ops->add_buf(vb->stats_vq,
+						  &sg, 1, 0, vb) < 0)
+			BUG();
+		vb->stats_vq->vq_ops->kick(vb->stats_vq);
+	}
+
 	vb->thread = kthread_run(balloon, vb, "vballoon");
 	if (IS_ERR(vb->thread)) {
 		err = PTR_ERR(vb->thread);
@@ -264,7 +339,10 @@
 	kfree(vb);
 }
  
-static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST };
+static unsigned int features[] = {
+	VIRTIO_BALLOON_F_MUST_TELL_HOST,
+	VIRTIO_BALLOON_F_STATS_VQ,
+};
  
 static struct virtio_driver virtio_balloon_driver = {
 	.feature_table = features,
@@ -7,6 +7,7 @@
  
 /* The feature bitmap for virtio balloon */
 #define VIRTIO_BALLOON_F_MUST_TELL_HOST	0 /* Tell before reclaiming pages */
+#define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */
  
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12
@@ -18,5 +19,19 @@
 	/* Number of pages we've actually got in balloon. */
 	__le32 actual;
 };
+
+#define VIRTIO_BALLOON_S_SWAP_IN  0   /* Amount of memory swapped in */
+#define VIRTIO_BALLOON_S_SWAP_OUT 1   /* Amount of memory swapped out */
+#define VIRTIO_BALLOON_S_MAJFLT   2   /* Number of major faults */
+#define VIRTIO_BALLOON_S_MINFLT   3   /* Number of minor faults */
+#define VIRTIO_BALLOON_S_MEMFREE  4   /* Total amount of free memory */
+#define VIRTIO_BALLOON_S_MEMTOT   5   /* Total amount of memory */
+#define VIRTIO_BALLOON_S_NR       6
+
+struct virtio_balloon_stat {
+	u16 tag;
+	u64 val;
+} __attribute__((packed));
+
 #endif /* _LINUX_VIRTIO_BALLOON_H */
...	...	@@ -28,7 +28,7 @@
28	28	struct virtio_balloon
29	29	{
30	30	struct virtio_device *vdev;
31		- struct virtqueue inflate_vq, deflate_vq;
	31	+ struct virtqueue inflate_vq, deflate_vq, *stats_vq;
32	32
33	33	/* Where the ballooning thread waits for config to change. */
34	34	wait_queue_head_t config_change;
...	...	@@ -49,6 +49,9 @@
49	49	/* The array of pfns we tell the Host about. */
50	50	unsigned int num_pfns;
51	51	u32 pfns[256];
	52	+
	53	+ /* Memory statistics */
	54	+ struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
52	55	};
53	56
54	57	static struct virtio_device_id id_table[] = {
...	...	@@ -154,6 +157,62 @@
154	157	}
155	158	}
156	159
	160	+static inline void update_stat(struct virtio_balloon *vb, int idx,
	161	+ u16 tag, u64 val)
	162	+{
	163	+ BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
	164	+ vb->stats[idx].tag = tag;
	165	+ vb->stats[idx].val = val;
	166	+}
	167	+
	168	+#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
	169	+
	170	+static void update_balloon_stats(struct virtio_balloon *vb)
	171	+{
	172	+ unsigned long events[NR_VM_EVENT_ITEMS];
	173	+ struct sysinfo i;
	174	+ int idx = 0;
	175	+
	176	+ all_vm_events(events);
	177	+ si_meminfo(&i);
	178	+
	179	+ update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
	180	+ pages_to_bytes(events[PSWPIN]));
	181	+ update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
	182	+ pages_to_bytes(events[PSWPOUT]));
	183	+ update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
	184	+ update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
	185	+ update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
	186	+ pages_to_bytes(i.freeram));
	187	+ update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
	188	+ pages_to_bytes(i.totalram));
	189	+}
	190	+
	191	+/*
	192	+ * While most virtqueues communicate guest-initiated requests to the hypervisor,
	193	+ * the stats queue operates in reverse. The driver initializes the virtqueue
	194	+ * with a single buffer. From that point forward, all conversations consist of
	195	+ * a hypervisor request (a call to this function) which directs us to refill
	196	+ * the virtqueue with a fresh stats buffer.
	197	+ */
	198	+static void stats_ack(struct virtqueue *vq)
	199	+{
	200	+ struct virtio_balloon *vb;
	201	+ unsigned int len;
	202	+ struct scatterlist sg;
	203	+
	204	+ vb = vq->vq_ops->get_buf(vq, &len);
	205	+ if (!vb)
	206	+ return;
	207	+
	208	+ update_balloon_stats(vb);
	209	+
	210	+ sg_init_one(&sg, vb->stats, sizeof(vb->stats));
	211	+ if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
	212	+ BUG();
	213	+ vq->vq_ops->kick(vq);
	214	+}
	215	+
157	216	static void virtballoon_changed(struct virtio_device *vdev)
158	217	{
159	218	struct virtio_balloon *vb = vdev->priv;
...	...	@@ -204,10 +263,10 @@
204	263	static int virtballoon_probe(struct virtio_device *vdev)
205	264	{
206	265	struct virtio_balloon *vb;
207		- struct virtqueue *vqs[2];
208		- vq_callback_t *callbacks[] = { balloon_ack, balloon_ack };
209		- const char *names[] = { "inflate", "deflate" };
210		- int err;
	266	+ struct virtqueue *vqs[3];
	267	+ vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_ack };
	268	+ const char *names[] = { "inflate", "deflate", "stats" };
	269	+ int err, nvqs;
211	270
212	271	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
213	272	if (!vb) {
214	273
215	274
...	...	@@ -220,14 +279,30 @@
220	279	init_waitqueue_head(&vb->config_change);
221	280	vb->vdev = vdev;
222	281
223		- /* We expect two virtqueues. */
224		- err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
	282	+ /* We expect two virtqueues: inflate and deflate,
	283	+ * and optionally stat. */
	284	+ nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
	285	+ err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
225	286	if (err)
226	287	goto out_free_vb;
227	288
228	289	vb->inflate_vq = vqs[0];
229	290	vb->deflate_vq = vqs[1];
	291	+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
	292	+ struct scatterlist sg;
	293	+ vb->stats_vq = vqs[2];
230	294
	295	+ /*
	296	+ * Prime this virtqueue with one buffer so the hypervisor can
	297	+ * use it to signal us later.
	298	+ */
	299	+ sg_init_one(&sg, vb->stats, sizeof vb->stats);
	300	+ if (vb->stats_vq->vq_ops->add_buf(vb->stats_vq,
	301	+ &sg, 1, 0, vb) < 0)
	302	+ BUG();
	303	+ vb->stats_vq->vq_ops->kick(vb->stats_vq);
	304	+ }
	305	+
231	306	vb->thread = kthread_run(balloon, vb, "vballoon");
232	307	if (IS_ERR(vb->thread)) {
233	308	err = PTR_ERR(vb->thread);
...	...	@@ -264,7 +339,10 @@
264	339	kfree(vb);
265	340	}
266	341
267		-static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST };
	342	+static unsigned int features[] = {
	343	+ VIRTIO_BALLOON_F_MUST_TELL_HOST,
	344	+ VIRTIO_BALLOON_F_STATS_VQ,
	345	+};
268	346
269	347	static struct virtio_driver virtio_balloon_driver = {
270	348	.feature_table = features,
...	...	@@ -7,6 +7,7 @@
7	7
8	8	/* The feature bitmap for virtio balloon */
9	9	#define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */
	10	+#define VIRTIO_BALLOON_F_STATS_VQ 1 /* Memory Stats virtqueue */
10	11
11	12	/* Size of a PFN in the balloon interface. */
12	13	#define VIRTIO_BALLOON_PFN_SHIFT 12
...	...	@@ -18,5 +19,19 @@
18	19	/* Number of pages we've actually got in balloon. */
19	20	__le32 actual;
20	21	};
	22	+
	23	+#define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */
	24	+#define VIRTIO_BALLOON_S_SWAP_OUT 1 /* Amount of memory swapped out */
	25	+#define VIRTIO_BALLOON_S_MAJFLT 2 /* Number of major faults */
	26	+#define VIRTIO_BALLOON_S_MINFLT 3 /* Number of minor faults */
	27	+#define VIRTIO_BALLOON_S_MEMFREE 4 /* Total amount of free memory */
	28	+#define VIRTIO_BALLOON_S_MEMTOT 5 /* Total amount of memory */
	29	+#define VIRTIO_BALLOON_S_NR 6
	30	+
	31	+struct virtio_balloon_stat {
	32	+ u16 tag;
	33	+ u64 val;
	34	+} __attribute__((packed));
	35	+
21	36	#endif /* _LINUX_VIRTIO_BALLOON_H */