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Subject: Re: [Qemu-devel] [PATCH v11 7/7] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT
* Wei Wang (wei.w.wang@intel.com) wrote:
> The new feature enables the virtio-balloon device to receive hints of
> guest free pages from the free page vq.
>
> A notifier is registered to the migration precopy notifier chain. The
> notifier calls free_page_start after the migration thread syncs the dirty
> bitmap, so that the free page optimization starts to clear bits of free
> pages from the bitmap. It calls the free_page_stop before the migration
> thread syncs the bitmap, which is the end of the current round of ram
> save. The free_page_stop is also called to stop the optimization in the
> case when there is an error occurred in the process of ram saving.
>
> Note: balloon will report pages which were free at the time of this call.
> As the reporting happens asynchronously, dirty bit logging must be
> enabled before this free_page_start call is made. Guest reporting must be
> disabled before the migration dirty bitmap is synchronized.
>
> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
> CC: Michael S. Tsirkin <mst@redhat.com>
> CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
> CC: Juan Quintela <quintela@redhat.com>
> CC: Peter Xu <peterx@redhat.com>
> ---
> hw/virtio/virtio-balloon.c | 263 ++++++++++++++++++++++++
> include/hw/virtio/virtio-balloon.h | 28 ++-
> include/standard-headers/linux/virtio_balloon.h | 5 +
> 3 files changed, 295 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> + if (dev->free_page_report_status == FREE_PAGE_REPORT_S_REQUESTED) {
> + config.free_page_report_cmd_id =
> + cpu_to_le32(dev->free_page_report_cmd_id);
> + } else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_STOP) {
> + config.free_page_report_cmd_id =
> + cpu_to_le32(VIRTIO_BALLOON_FREE_PAGE_REPORT_STOP_ID);
> + } else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_DONE) {
> + config.free_page_report_cmd_id =
> + cpu_to_le32(VIRTIO_BALLOON_FREE_PAGE_REPORT_DONE_ID);
> + }
It looks like somewhere in the last 3 months the name in the kernel
changed; so I think I've fixed this correctly but please shout if it's
wrong:
if (dev->free_page_report_status == FREE_PAGE_REPORT_S_REQUESTED) {
config.free_page_report_cmd_id =
cpu_to_le32(dev->free_page_report_cmd_id);
} else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_STOP) {
config.free_page_report_cmd_id =
cpu_to_le32(VIRTIO_BALLOON_CMD_ID_STOP);
} else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_DONE) {
config.free_page_report_cmd_id =
cpu_to_le32(VIRTIO_BALLOON_CMD_ID_DONE);
}
and I've dropped the kernel header update since it's already there.
Dave
> +
> trace_virtio_balloon_get_config(config.num_pages, config.actual);
> memcpy(config_data, &config, sizeof(struct virtio_balloon_config));
> }
> @@ -376,6 +566,7 @@ static uint64_t virtio_balloon_get_features(VirtIODevice *vdev, uint64_t f,
> VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
> f |= dev->host_features;
> virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ);
> +
> return f;
> }
>
> @@ -412,6 +603,18 @@ static int virtio_balloon_post_load_device(void *opaque, int version_id)
> return 0;
> }
>
> +static const VMStateDescription vmstate_virtio_balloon_free_page_report = {
> + .name = "virtio-balloon-device/free-page-report",
> + .version_id = 1,
> + .minimum_version_id = 1,
> + .needed = virtio_balloon_free_page_support,
> + .fields = (VMStateField[]) {
> + VMSTATE_UINT32(free_page_report_cmd_id, VirtIOBalloon),
> + VMSTATE_UINT32(free_page_report_status, VirtIOBalloon),
> + VMSTATE_END_OF_LIST()
> + }
> +};
> +
> static const VMStateDescription vmstate_virtio_balloon_device = {
> .name = "virtio-balloon-device",
> .version_id = 1,
> @@ -422,6 +625,10 @@ static const VMStateDescription vmstate_virtio_balloon_device = {
> VMSTATE_UINT32(actual, VirtIOBalloon),
> VMSTATE_END_OF_LIST()
> },
> + .subsections = (const VMStateDescription * []) {
> + &vmstate_virtio_balloon_free_page_report,
> + NULL
> + }
> };
>
> static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
> @@ -446,6 +653,29 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
> s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
>
> + if (virtio_has_feature(s->host_features,
> + VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
> + s->free_page_vq = virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE,
> + virtio_balloon_handle_free_page_vq);
> + s->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
> + s->free_page_report_cmd_id =
> + VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN;
> + s->free_page_report_notify.notify =
> + virtio_balloon_free_page_report_notify;
> + precopy_add_notifier(&s->free_page_report_notify);
> + if (s->iothread) {
> + object_ref(OBJECT(s->iothread));
> + s->free_page_bh = aio_bh_new(iothread_get_aio_context(s->iothread),
> + virtio_ballloon_get_free_page_hints, s);
> + qemu_mutex_init(&s->free_page_lock);
> + qemu_cond_init(&s->free_page_cond);
> + s->block_iothread = false;
> + } else {
> + /* Simply disable this feature if the iothread wasn't created. */
> + s->host_features &= ~(1 << VIRTIO_BALLOON_F_FREE_PAGE_HINT);
> + virtio_error(vdev, "iothread is missing");
> + }
> + }
> reset_stats(s);
> }
>
> @@ -454,6 +684,11 @@ static void virtio_balloon_device_unrealize(DeviceState *dev, Error **errp)
> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> VirtIOBalloon *s = VIRTIO_BALLOON(dev);
>
> + if (virtio_balloon_free_page_support(s)) {
> + qemu_bh_delete(s->free_page_bh);
> + virtio_balloon_free_page_stop(s);
> + precopy_remove_notifier(&s->free_page_report_notify);
> + }
> balloon_stats_destroy_timer(s);
> qemu_remove_balloon_handler(s);
> virtio_cleanup(vdev);
> @@ -463,6 +698,10 @@ static void virtio_balloon_device_reset(VirtIODevice *vdev)
> {
> VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
>
> + if (virtio_balloon_free_page_support(s)) {
> + virtio_balloon_free_page_stop(s);
> + }
> +
> if (s->stats_vq_elem != NULL) {
> virtqueue_unpop(s->svq, s->stats_vq_elem, 0);
> g_free(s->stats_vq_elem);
> @@ -480,6 +719,26 @@ static void virtio_balloon_set_status(VirtIODevice *vdev, uint8_t status)
> * was stopped */
> virtio_balloon_receive_stats(vdev, s->svq);
> }
> +
> + if (virtio_balloon_free_page_support(s)) {
> + /*
> + * The VM is woken up and the iothread was blocked, so signal it to
> + * continue.
> + */
> + if (vdev->vm_running && s->block_iothread) {
> + qemu_mutex_lock(&s->free_page_lock);
> + s->block_iothread = false;
> + qemu_cond_signal(&s->free_page_cond);
> + qemu_mutex_unlock(&s->free_page_lock);
> + }
> +
> + /* The VM is stopped, block the iothread. */
> + if (!vdev->vm_running) {
> + qemu_mutex_lock(&s->free_page_lock);
> + s->block_iothread = true;
> + qemu_mutex_unlock(&s->free_page_lock);
> + }
> + }
> }
>
> static void virtio_balloon_instance_init(Object *obj)
> @@ -508,6 +767,10 @@ static const VMStateDescription vmstate_virtio_balloon = {
> static Property virtio_balloon_properties[] = {
> DEFINE_PROP_BIT("deflate-on-oom", VirtIOBalloon, host_features,
> VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false),
> + DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features,
> + VIRTIO_BALLOON_F_FREE_PAGE_HINT, false),
> + DEFINE_PROP_LINK("iothread", VirtIOBalloon, iothread, TYPE_IOTHREAD,
> + IOThread *),
> DEFINE_PROP_END_OF_LIST(),
> };
>
> diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
> index e0df352..503349a 100644
> --- a/include/hw/virtio/virtio-balloon.h
> +++ b/include/hw/virtio/virtio-balloon.h
> @@ -17,11 +17,14 @@
>
> #include "standard-headers/linux/virtio_balloon.h"
> #include "hw/virtio/virtio.h"
> +#include "sysemu/iothread.h"
>
> #define TYPE_VIRTIO_BALLOON "virtio-balloon-device"
> #define VIRTIO_BALLOON(obj) \
> OBJECT_CHECK(VirtIOBalloon, (obj), TYPE_VIRTIO_BALLOON)
>
> +#define VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN 0x80000000
> +
> typedef struct virtio_balloon_stat VirtIOBalloonStat;
>
> typedef struct virtio_balloon_stat_modern {
> @@ -30,15 +33,38 @@ typedef struct virtio_balloon_stat_modern {
> uint64_t val;
> } VirtIOBalloonStatModern;
>
> +enum virtio_balloon_free_page_report_status {
> + FREE_PAGE_REPORT_S_STOP = 0,
> + FREE_PAGE_REPORT_S_REQUESTED = 1,
> + FREE_PAGE_REPORT_S_START = 2,
> + FREE_PAGE_REPORT_S_DONE = 3,
> +};
> +
> typedef struct VirtIOBalloon {
> VirtIODevice parent_obj;
> - VirtQueue *ivq, *dvq, *svq;
> + VirtQueue *ivq, *dvq, *svq, *free_page_vq;
> + uint32_t free_page_report_status;
> uint32_t num_pages;
> uint32_t actual;
> + uint32_t free_page_report_cmd_id;
> uint64_t stats[VIRTIO_BALLOON_S_NR];
> VirtQueueElement *stats_vq_elem;
> size_t stats_vq_offset;
> QEMUTimer *stats_timer;
> + IOThread *iothread;
> + QEMUBH *free_page_bh;
> + /*
> + * Lock to synchronize threads to access the free page reporting related
> + * fields (e.g. free_page_report_status).
> + */
> + QemuMutex free_page_lock;
> + QemuCond free_page_cond;
> + /*
> + * Set to block iothread to continue reading free page hints as the VM is
> + * stopped.
> + */
> + bool block_iothread;
> + NotifierWithReturn free_page_report_notify;
> int64_t stats_last_update;
> int64_t stats_poll_interval;
> uint32_t host_features;
> diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h
> index 4dbb7dc..9eee1c6 100644
> --- a/include/standard-headers/linux/virtio_balloon.h
> +++ b/include/standard-headers/linux/virtio_balloon.h
> @@ -34,15 +34,20 @@
> #define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */
> #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_FREE_PAGE_HINT 3 /* VQ to report free pages */
>
> /* Size of a PFN in the balloon interface. */
> #define VIRTIO_BALLOON_PFN_SHIFT 12
>
> +#define VIRTIO_BALLOON_FREE_PAGE_REPORT_STOP_ID 0
> +#define VIRTIO_BALLOON_FREE_PAGE_REPORT_DONE_ID 1
> struct virtio_balloon_config {
> /* Number of pages host wants Guest to give up. */
> uint32_t num_pages;
> /* Number of pages we've actually got in balloon. */
> uint32_t actual;
> + /* Free page report command id, readonly by guest */
> + uint32_t free_page_report_cmd_id;
> };
>
> #define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */
> --
> 1.8.3.1
>
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
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