On Mon, Jun 13, 2016 at 06:16:44PM +0800, Liang Li wrote:
> virtio-balloon can make use of the amount of free memory to determine
> the amount of memory to be filled in the balloon, but the amount of
> free memory will be effected by the page cache, which can be reclaimed.
> Drop the cache before getting the amount of free memory will be very
> helpful to relect the exact amount of memroy that can be reclaimed.
Can't we just extend stats to report "reclaimable" memory?
> This patch add a new feature to the balloon device to support this
> operation, hypervisor can request the VM to drop it's cache, so as to
> reclaim more memory.
>
> Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
> ---
> balloon.c | 10 ++-
> hw/virtio/virtio-balloon.c | 85 ++++++++++++++++++++++++-
> include/hw/virtio/virtio-balloon.h | 19 +++++-
> include/standard-headers/linux/virtio_balloon.h | 1 +
> include/sysemu/balloon.h | 5 +-
> 5 files changed, 115 insertions(+), 5 deletions(-)
>
> diff --git a/balloon.c b/balloon.c
> index f2ef50c..0fb34bf 100644
> --- a/balloon.c
> +++ b/balloon.c
> @@ -36,6 +36,7 @@
>
> static QEMUBalloonEvent *balloon_event_fn;
> static QEMUBalloonStatus *balloon_stat_fn;
> +static QEMUBalloonDropCache *balloon_drop_cache_fn;
> static void *balloon_opaque;
> static bool balloon_inhibited;
>
> @@ -65,9 +66,12 @@ static bool have_balloon(Error **errp)
> }
>
> int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
> - QEMUBalloonStatus *stat_func, void *opaque)
> + QEMUBalloonStatus *stat_func,
> + QEMUBalloonDropCache *drop_cache_func,
> + void *opaque)
> {
> - if (balloon_event_fn || balloon_stat_fn || balloon_opaque) {
> + if (balloon_event_fn || balloon_stat_fn || balloon_drop_cache_fn
> + || balloon_opaque) {
> /* We're already registered one balloon handler. How many can
> * a guest really have?
> */
> @@ -75,6 +79,7 @@ int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
> }
> balloon_event_fn = event_func;
> balloon_stat_fn = stat_func;
> + balloon_drop_cache_fn = drop_cache_func;
> balloon_opaque = opaque;
> return 0;
> }
> @@ -86,6 +91,7 @@ void qemu_remove_balloon_handler(void *opaque)
> }
> balloon_event_fn = NULL;
> balloon_stat_fn = NULL;
> + balloon_drop_cache_fn = NULL;
> balloon_opaque = NULL;
> }
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index 8cf74c2..4757ba5 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -36,6 +36,10 @@
>
> #define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT)
>
> +enum balloon_req_id {
> + BALLOON_DROP_CACHE,
> +};
> +
> static void balloon_page(void *addr, int deflate)
> {
> #if defined(__linux__)
> @@ -154,6 +158,12 @@ static bool balloon_page_bitmap_supported(const VirtIOBalloon *s)
> return virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_BITMAP);
> }
>
> +static bool balloon_misc_supported(const VirtIOBalloon *s)
> +{
> + VirtIODevice *vdev = VIRTIO_DEVICE(s);
> + return virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_MISC);
> +}
> +
> static bool balloon_stats_enabled(const VirtIOBalloon *s)
> {
> return s->stats_poll_interval > 0;
> @@ -420,6 +430,39 @@ out:
> }
> }
>
> +static void virtio_balloon_handle_resp(VirtIODevice *vdev, VirtQueue *vq)
> +{
> + VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
> + VirtQueueElement *elem;
> + size_t offset = 0;
> + uint32_t tmp32, id = 0;
> +
> + elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> + if (!elem) {
> + s->req_status = REQ_ERROR;
> + return;
> + }
> +
> + s->misc_vq_elem = elem;
> +
> + if (!elem->out_num) {
> + return;
> + }
> +
> + iov_to_buf(elem->out_sg, elem->out_num, offset,
> + &tmp32, sizeof(uint32_t));
> + id = virtio_ldl_p(vdev, &tmp32);
> + offset += sizeof(uint32_t);
> + switch (id) {
> + case BALLOON_DROP_CACHE:
> + s->req_status = REQ_DONE;
> + break;
> + default:
> + break;
> + }
> +
> +}
> +
> static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
> {
> VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
> @@ -490,6 +533,7 @@ static uint64_t virtio_balloon_get_features(VirtIODevice *vdev, uint64_t f,
> f |= dev->host_features;
> virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ);
> virtio_add_feature(&f, VIRTIO_BALLOON_F_PAGE_BITMAP);
> + virtio_add_feature(&f, VIRTIO_BALLOON_F_MISC);
> return f;
> }
>
> @@ -500,6 +544,36 @@ static void virtio_balloon_stat(void *opaque, BalloonInfo *info)
> VIRTIO_BALLOON_PFN_SHIFT);
> }
>
> +static int virtio_balloon_drop_cache(void *opaque, unsigned long type)
> +{
> + VirtIOBalloon *s = opaque;
> + VirtIODevice *vdev = VIRTIO_DEVICE(s);
> + VirtQueueElement *elem = s->misc_vq_elem;
> + int len;
> +
> + if (!balloon_misc_supported(s)) {
> + return REQ_UNSUPPORT;
> + }
> +
> + if (elem == NULL || !elem->in_num) {
> + elem = virtqueue_pop(s->mvq, sizeof(VirtQueueElement));
> + if (!elem) {
> + return REQ_ERROR;
> + }
> + s->misc_vq_elem = elem;
> + }
> + s->misc_req.id = BALLOON_DROP_CACHE;
> + s->misc_req.param = type;
> + len = iov_from_buf(elem->in_sg, elem->in_num, 0, &s->misc_req,
> + sizeof(s->misc_req));
> + virtqueue_push(s->mvq, elem, len);
> + virtio_notify(vdev, s->mvq);
> + g_free(s->misc_vq_elem);
> + s->misc_vq_elem = NULL;
> +
> + return REQ_DONE;
> +}
> +
> static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
> {
> VirtIOBalloon *dev = VIRTIO_BALLOON(opaque);
> @@ -562,7 +636,8 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
> sizeof(struct virtio_balloon_config));
>
> ret = qemu_add_balloon_handler(virtio_balloon_to_target,
> - virtio_balloon_stat, s);
> + virtio_balloon_stat,
> + virtio_balloon_drop_cache, s);
>
> if (ret < 0) {
> error_setg(errp, "Only one balloon device is supported");
> @@ -573,8 +648,10 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
> s->ivq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
> + s->mvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_resp);
>
> reset_stats(s);
> + s->req_status = REQ_INIT;
>
> register_savevm(dev, "virtio-balloon", -1, 1,
> virtio_balloon_save, virtio_balloon_load, s);
> @@ -599,6 +676,12 @@ static void virtio_balloon_device_reset(VirtIODevice *vdev)
> g_free(s->stats_vq_elem);
> s->stats_vq_elem = NULL;
> }
> +
> + if (s->misc_vq_elem != NULL) {
> + g_free(s->misc_vq_elem);
> + s->misc_vq_elem = NULL;
> + }
> + s->req_status = REQ_INIT;
> }
>
> static void virtio_balloon_instance_init(Object *obj)
> diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
> index 35f62ac..a21bb45 100644
> --- a/include/hw/virtio/virtio-balloon.h
> +++ b/include/hw/virtio/virtio-balloon.h
> @@ -23,6 +23,20 @@
> #define VIRTIO_BALLOON(obj) \
> OBJECT_CHECK(VirtIOBalloon, (obj), TYPE_VIRTIO_BALLOON)
>
> +typedef enum {
> + REQ_INIT,
> + REQ_ON_GOING,
> + REQ_DONE,
> + REQ_ERROR,
> + REQ_INVALID_PARAM,
> + REQ_UNSUPPORT,
> +} BalloonReqStatus;
> +
> +typedef struct GetFreePageReq {
> + uint32_t id;
> + uint32_t param;
> +} MiscReq;
> +
> typedef struct virtio_balloon_stat VirtIOBalloonStat;
>
> typedef struct virtio_balloon_stat_modern {
> @@ -33,16 +47,19 @@ typedef struct virtio_balloon_stat_modern {
>
> typedef struct VirtIOBalloon {
> VirtIODevice parent_obj;
> - VirtQueue *ivq, *dvq, *svq;
> + VirtQueue *ivq, *dvq, *svq, *mvq;
> uint32_t num_pages;
> uint32_t actual;
> uint64_t stats[VIRTIO_BALLOON_S_NR];
> VirtQueueElement *stats_vq_elem;
> + VirtQueueElement *misc_vq_elem;
> size_t stats_vq_offset;
> QEMUTimer *stats_timer;
> int64_t stats_last_update;
> int64_t stats_poll_interval;
> uint32_t host_features;
> + MiscReq misc_req;
> + BalloonReqStatus req_status;
> } VirtIOBalloon;
>
> #endif
> diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h
> index 7c9686c..c8b254f 100644
> --- a/include/standard-headers/linux/virtio_balloon.h
> +++ b/include/standard-headers/linux/virtio_balloon.h
> @@ -35,6 +35,7 @@
> #define VIRTIO_BALLOON_F_STATS_VQ 1 /* Memory Stats virtqueue */
> #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
> #define VIRTIO_BALLOON_F_PAGE_BITMAP 3 /* Use page bitmap to send page info */
> +#define VIRTIO_BALLOON_F_MISC 4 /* Send request and get misc info */
>
> /* Size of a PFN in the balloon interface. */
> #define VIRTIO_BALLOON_PFN_SHIFT 12
> diff --git a/include/sysemu/balloon.h b/include/sysemu/balloon.h
> index 3f976b4..0e85f2b 100644
> --- a/include/sysemu/balloon.h
> +++ b/include/sysemu/balloon.h
> @@ -18,9 +18,12 @@
>
> typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target);
> typedef void (QEMUBalloonStatus)(void *opaque, BalloonInfo *info);
> +typedef int (QEMUBalloonDropCache)(void *opaque, unsigned long ctrl);
>
> int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
> - QEMUBalloonStatus *stat_func, void *opaque);
> + QEMUBalloonStatus *stat_func,
> + QEMUBalloonDropCache *drop_cache_func,
> + void *opaque);
> void qemu_remove_balloon_handler(void *opaque);
> bool qemu_balloon_is_inhibited(void);
> void qemu_balloon_inhibit(bool state);
> --
> 1.9.1
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
