virtio: Add memory statistics reporting to the balloon driver (V2)
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 <a...@us.ibm.com>
Cc: Rusty Russell <ru...@rustcorp.com.au>
Cc: Anthony Liguori <anth...@codemonkey.ws>
Cc: virtualizat...@lists.linux-foundation.org
Cc: linux-ker...@vger.kernel.org
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 200c22f..59b9533 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -29,7 +29,7 @@
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;
@@ -50,6 +50,9 @@ struct virtio_balloon
/* 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[] = {
@@ -155,6 +158,60 @@ static void leak_balloon(struct virtio_balloon *vb, size_t
num)
}
}
+static inline void update_stat(struct virtio_balloon *vb, int idx,
+ unsigned int tag, unsigned long val)
+{
+ BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
+ vb->stats[idx].tag = tag;
+ vb->stats[idx].val = cpu_to_le32(val);
+}
+
+#define K(x) ((x) << (PAGE_SHIFT - 10))
+static void update_balloon_stats(struct virtio_balloon *vb)
+{
+ unsigned long events[NR_VM_EVENT_ITEMS];
+ struct sysinfo i;
+ unsigned long anon_pages;
+ int idx = 0;
+
+ all_vm_events(events);
+ si_meminfo(&i);
+ anon_pages = K(global_page_state(NR_ANON_PAGES));
+
+ update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, events[PSWPIN]);
+ update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, events[PSWPOUT]);
+ update_stat(vb, idx++, VIRTIO_BALLOON_S_ANON, anon_pages);
+ 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, K(i.freeram));
+ update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, K(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;
@@ -205,10 +262,10 @@ static int balloon(void *_vballoon)
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) {
@@ -221,13 +278,28 @@ static int virtballoon_probe(struct virtio_device *vdev)
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)) {
@@ -265,7 +337,9 @@ static void virtballoon_remove(struct virtio_device *vdev)
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 = {
.feature_table = features,
diff --git a/include/linux/virtio_balloon.h b/include/linux/virtio_balloon.h
index 09d7300..3d21b9f 100644
--- a/include/linux/virtio_balloon.h
+++ b/include/linux/virtio_balloon.h
@@ -6,6 +6,7 @@
/* 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
@@ -17,4 +18,20 @@ struct virtio_balloon_config
/* Number of pages we've actually got in balloon. */
__le32 actual;
};
+
+#define VIRTIO_BALLOON_S_SWAP_IN 0 /* Number of pages swapped in */
+#define VIRTIO_BALLOON_S_SWAP_OUT 1 /* Number of pages swapped out */
+#define VIRTIO_BALLOON_S_ANON 2 /* Number of anonymous pages in use */
+#define VIRTIO_BALLOON_S_MAJFLT 3 /* Number of major faults */
+#define VIRTIO_BALLOON_S_MINFLT 4 /* Number of minor faults */
+#define VIRTIO_BALLOON_S_MEMFREE 5 /* Total amount of free memory */
+#define VIRTIO_BALLOON_S_MEMTOT 6 /* Total amount of memory */
+#define VIRTIO_BALLOON_S_NR 7
+
+struct virtio_balloon_stat
+{
+ __le16 tag;
+ __le32 val;
+};
+
#endif /* _LINUX_VIRTIO_BALLOON_H */
--
Thanks,
Adam
