Re: [PATCH v10 3/6] virtio-balloon: VIRTIO_BALLOON_F_PAGE_CHUNKS

Michael S. Tsirkin
2017-05-05T22:29:05Z

On Thu, May 04, 2017 at 04:50:12PM +0800, Wei Wang wrote:
> Add a new feature, VIRTIO_BALLOON_F_PAGE_CHUNKS, which enables
> the transfer of the ballooned (i.e. inflated/deflated) pages in
> chunks to the host.
>
> The implementation of the previous virtio-balloon is not very
> efficient, because the ballooned pages are transferred to the
> host one by one. Here is the breakdown of the time in percentage
> spent on each step of the balloon inflating process (inflating
> 7GB of an 8GB idle guest).
>
> 1) allocating pages (6.5%)
> 2) sending PFNs to host (68.3%)
> 3) address translation (6.1%)
> 4) madvise (19%)
>
> It takes about 4126ms for the inflating process to complete.
> The above profiling shows that the bottlenecks are stage 2)
> and stage 4).
>
> This patch optimizes step 2) by transferring pages to the host in
> chunks. A chunk consists of guest physically continuous pages.
> When the pages are packed into a chunk, they are converted into
> balloon page size (4KB) pages. A chunk is offered to the host
> via a base PFN (i.e. the start PFN of those physically continuous
> pages) and the size (i.e. the total number of the 4KB balloon size
> pages). A chunk is formatted as below:
> --------------------------------------------------------
> | Base (52 bit) | Rsvd (12 bit) |
> --------------------------------------------------------
> --------------------------------------------------------
> | Size (52 bit) | Rsvd (12 bit) |
> --------------------------------------------------------
>
> By doing so, step 4) can also be optimized by doing address
> translation and madvise() in chunks rather than page by page.
>
> With this new feature, the above ballooning process takes ~590ms
> resulting in an improvement of ~85%.
>
> TODO: optimize stage 1) by allocating/freeing a chunk of pages
> instead of a single page each time.
>
> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
> Signed-off-by: Liang Li <liang.z.li@intel.com>
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>

This is much cleaner, thanks. It might be even better to
have wrappers that put array and its size in a struct
and manage that struct, but I won't require this for
submission.

> ---
> drivers/virtio/virtio_balloon.c | 407 +++++++++++++++++++++++++++++++++---
> include/uapi/linux/virtio_balloon.h | 14 ++
> 2 files changed, 396 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index ecb64e9..df16912 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -43,6 +43,20 @@
> #define OOM_VBALLOON_DEFAULT_PAGES 256
> #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
>
> +/* The size of one page_bmap used to record inflated/deflated pages. */
> +#define VIRTIO_BALLOON_PAGE_BMAP_SIZE (8 * PAGE_SIZE)
> +/*
> + * Callulates how many pfns can a page_bmap record. A bit corresponds to a
> + * page of PAGE_SIZE.
> + */
> +#define VIRTIO_BALLOON_PFNS_PER_PAGE_BMAP \
> + (VIRTIO_BALLOON_PAGE_BMAP_SIZE * BITS_PER_BYTE)
> +
> +/* The number of page_bmap to allocate by default. */
> +#define VIRTIO_BALLOON_PAGE_BMAP_DEFAULT_NUM 1
> +/* The maximum number of page_bmap that can be allocated. */
> +#define VIRTIO_BALLOON_PAGE_BMAP_MAX_NUM 32
> +
> static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
> module_param(oom_pages, int, S_IRUSR | S_IWUSR);
> MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
> @@ -51,6 +65,11 @@ MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
> static struct vfsmount *balloon_mnt;
> #endif
>
> +/* Maximum number of page chunks */
> +#define VIRTIO_BALLOON_MAX_PAGE_CHUNKS ((8 * PAGE_SIZE - \
> + sizeof(struct virtio_balloon_page_chunk)) / \
> + sizeof(struct virtio_balloon_page_chunk_entry))
> +
> struct virtio_balloon {
> struct virtio_device *vdev;
> struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
> @@ -79,6 +98,12 @@ struct virtio_balloon {
> /* Synchronize access/update to this struct virtio_balloon elements */
> struct mutex balloon_lock;
>
> + /* Buffer for chunks of ballooned pages. */
> + struct virtio_balloon_page_chunk *balloon_page_chunk;
> +
> + /* Bitmap used to record pages. */
> + unsigned long *page_bmap[VIRTIO_BALLOON_PAGE_BMAP_MAX_NUM];
> +
> /* The array of pfns we tell the Host about. */
> unsigned int num_pfns;
> __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
> @@ -111,6 +136,136 @@ static void balloon_ack(struct virtqueue *vq)
> wake_up(&vb->acked);
> }
>
> +/* Update pfn_max and pfn_min according to the pfn of page */
> +static inline void update_pfn_range(struct virtio_balloon *vb,
> + struct page *page,
> + unsigned long *pfn_min,
> + unsigned long *pfn_max)
> +{
> + unsigned long pfn = page_to_pfn(page);
> +
> + *pfn_min = min(pfn, *pfn_min);
> + *pfn_max = max(pfn, *pfn_max);
> +}
> +
> +static unsigned int extend_page_bmap_size(struct virtio_balloon *vb,
> + unsigned long pfn_num)
> +{
> + unsigned int i, bmap_num, allocated_bmap_num;
> + unsigned long bmap_len;
> +
> + allocated_bmap_num = VIRTIO_BALLOON_PAGE_BMAP_DEFAULT_NUM;
> + bmap_len = ALIGN(pfn_num, BITS_PER_LONG) / BITS_PER_BYTE;
> + bmap_len = roundup(bmap_len, VIRTIO_BALLOON_PAGE_BMAP_SIZE);
> + /*
> + * VIRTIO_BALLOON_PAGE_BMAP_SIZE is the size of one page_bmap, so
> + * divide it to calculate how many page_bmap that we need.
> + */
> + bmap_num = (unsigned int)(bmap_len / VIRTIO_BALLOON_PAGE_BMAP_SIZE);
> + /* The number of page_bmap

... arrays ...

> to allocate should not exceed the max */
> + bmap_num = min_t(unsigned int, VIRTIO_BALLOON_PAGE_BMAP_MAX_NUM,
> + bmap_num);
> +
> + for (i = VIRTIO_BALLOON_PAGE_BMAP_DEFAULT_NUM; i < bmap_num; i++) {
> + vb->page_bmap[i] = kmalloc(VIRTIO_BALLOON_PAGE_BMAP_SIZE,
> + GFP_KERNEL);
> + if (vb->page_bmap[i])
> + allocated_bmap_num++;
> + else
> + break;
> + }
> +
> + return allocated_bmap_num;
> +}
> +
> +static void free_extended_page_bmap(struct virtio_balloon *vb,
> + unsigned int page_bmap_num)
> +{
> + unsigned int i;
> +
> + for (i = VIRTIO_BALLOON_PAGE_BMAP_DEFAULT_NUM; i < page_bmap_num;
> + i++) {
> + kfree(vb->page_bmap[i]);
> + vb->page_bmap[i] = NULL;
> + page_bmap_num--;
> + }
> +}
> +
> +static void clear_page_bmap(struct virtio_balloon *vb,
> + unsigned int page_bmap_num)
> +{
> + int i;
> +
> + for (i = 0; i < page_bmap_num; i++)
> + memset(vb->page_bmap[i], 0, VIRTIO_BALLOON_PAGE_BMAP_SIZE);
> +}
> +
> +static void send_page_chunks(struct virtio_balloon *vb, struct virtqueue *vq)
> +{
> + struct scatterlist sg;
> + struct virtio_balloon_page_chunk *chunk;
> + unsigned int len;
> +
> + chunk = vb->balloon_page_chunk;
> + len = sizeof(__le64) +
> + le64_to_cpu(chunk->chunk_num) *
> + sizeof(struct virtio_balloon_page_chunk_entry);
> + sg_init_one(&sg, chunk, len);
> + if (!virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL)) {
> + virtqueue_kick(vq);
> + wait_event(vb->acked, virtqueue_get_buf(vq, &len));
> + chunk->chunk_num = 0;
> + }
> +}
> +
> +/* Add a chunk entry to the buffer. */
> +static void add_one_chunk(struct virtio_balloon *vb, struct virtqueue *vq,
> + u64 base, u64 size)
> +{
> + struct virtio_balloon_page_chunk *chunk = vb->balloon_page_chunk;
> + struct virtio_balloon_page_chunk_entry *entry;
> + uint64_t chunk_num = le64_to_cpu(chunk->chunk_num);
> +
> + entry = &chunk->entry[chunk_num];
> + entry->base = cpu_to_le64(base << VIRTIO_BALLOON_CHUNK_BASE_SHIFT);
> + entry->size = cpu_to_le64(size << VIRTIO_BALLOON_CHUNK_SIZE_SHIFT);
> + chunk->chunk_num = cpu_to_le64(++chunk_num);
> + if (chunk_num == VIRTIO_BALLOON_MAX_PAGE_CHUNKS)
> + send_page_chunks(vb, vq);
> +}
> +
> +static void convert_bmap_to_chunks(struct virtio_balloon *vb,
> + struct virtqueue *vq,
> + unsigned long *bmap,
> + unsigned long pfn_start,
> + unsigned long size)
> +{
> + unsigned long next_one, next_zero, chunk_size, pos = 0;
> +
> + while (pos < size) {
> + next_one = find_next_bit(bmap, size, pos);
> + /*
> + * No "1" bit found, which means that there is no pfn
> + * recorded in the rest of this bmap.
> + */
> + if (next_one == size)
> + break;
> + next_zero = find_next_zero_bit(bmap, size, next_one + 1);
> + /*
> + * A bit in page_bmap corresponds to a page of PAGE_SIZE.
> + * Convert it to be pages of 4KB balloon page size when
> + * adding it to a chunk.
> + */
> + chunk_size = (next_zero - next_one) *
> + VIRTIO_BALLOON_PAGES_PER_PAGE;
> + if (chunk_size) {
> + add_one_chunk(vb, vq, pfn_start + next_one,
> + chunk_size);
> + pos += next_zero + 1;
> + }
> + }
> +}
> +
> static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
> {
> struct scatterlist sg;
> @@ -124,7 +279,33 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
>
> /* When host has read buffer, this completes via balloon_ack */
> wait_event(vb->acked, virtqueue_get_buf(vq, &len));
> +}
> +
> +static void tell_host_from_page_bmap(struct virtio_balloon *vb,
> + struct virtqueue *vq,
> + unsigned long pfn_start,
> + unsigned long pfn_end,
> + unsigned int page_bmap_num)
> +{
> + unsigned long i, pfn_num;
>
> + for (i = 0; i < page_bmap_num; i++) {
> + /*
> + * For the last page_bmap, only the remaining number of pfns
> + * need to be searched rather than the entire page_bmap.
> + */
> + if (i + 1 == page_bmap_num)
> + pfn_num = (pfn_end - pfn_start) %
> + VIRTIO_BALLOON_PFNS_PER_PAGE_BMAP;
> + else
> + pfn_num = VIRTIO_BALLOON_PFNS_PER_PAGE_BMAP;
> +
> + convert_bmap_to_chunks(vb, vq, vb->page_bmap[i], pfn_start +
> + i * VIRTIO_BALLOON_PFNS_PER_PAGE_BMAP,
> + pfn_num);
> + }
> + if (le64_to_cpu(vb->balloon_page_chunk->chunk_num) > 0)
> + send_page_chunks(vb, vq);
> }
>
> static void set_page_pfns(struct virtio_balloon *vb,
> @@ -141,13 +322,88 @@ static void set_page_pfns(struct virtio_balloon *vb,
> page_to_balloon_pfn(page) + i);
> }
>
> +/*
> + * Send ballooned pages in chunks to host.
> + * The ballooned pages are recorded in page bitmaps. Each bit in a bitmap
> + * corresponds to a page of PAGE_SIZE. The page bitmaps are searched for
> + * continuous "1" bits, which correspond to continuous pages, to chunk.
> + * When packing those continuous pages into chunks, pages are converted into
> + * 4KB balloon pages.
> + *
> + * pfn_max and pfn_min form the range of pfns that need to use page bitmaps to
> + * record. If the range is too large to be recorded into the allocated page
> + * bitmaps, the page bitmaps are used multiple times to record the entire
> + * range of pfns.
> + */
> +static void tell_host_page_chunks(struct virtio_balloon *vb,
> + struct list_head *pages,
> + struct virtqueue *vq,
> + unsigned long pfn_max,
> + unsigned long pfn_min)
> +{
> + /*
> + * The pfn_start and pfn_end form the range of pfns that the allocated
> + * page_bmap can record in each round.
> + */
> + unsigned long pfn_start, pfn_end;
> + /* Total number of allocated page_bmap

arrays

> */
> + unsigned int page_bmap_num;
> + struct page *page;
> + bool found;
> +
> + /*
> + * In the case that one page_bmap is not sufficient to record the pfn
> + * range, page_bmap will be extended by allocating more numbers of
> + * page_bmap.
> + */
> + page_bmap_num = extend_page_bmap_size(vb, pfn_max - pfn_min + 1);
> +
> + /* Start from the beginning of the whole pfn range */
> + pfn_start = pfn_min;
> + while (pfn_start < pfn_max) {
> + pfn_end = pfn_start +
> + VIRTIO_BALLOON_PFNS_PER_PAGE_BMAP * page_bmap_num;
> + pfn_end = pfn_end < pfn_max ? pfn_end : pfn_max;
> + clear_page_bmap(vb, page_bmap_num);
> + found = false;
> +
> + list_for_each_entry(page, pages, lru) {
> + unsigned long bmap_idx, bmap_pos, this_pfn;
> +
> + this_pfn = page_to_pfn(page);
> + if (this_pfn < pfn_start || this_pfn > pfn_end)
> + continue;
> + bmap_idx = (this_pfn - pfn_start) /
> + VIRTIO_BALLOON_PFNS_PER_PAGE_BMAP;
> + bmap_pos = (this_pfn - pfn_start) %
> + VIRTIO_BALLOON_PFNS_PER_PAGE_BMAP;
> + set_bit(bmap_pos, vb->page_bmap[bmap_idx]);
> +
> + found = true;
> + }
> + if (found)
> + tell_host_from_page_bmap(vb, vq, pfn_start, pfn_end,
> + page_bmap_num);
> + /*
> + * Start the next round when pfn_start and pfn_end couldn't
> + * cover the whole pfn range given by pfn_max and pfn_min.
> + */
> + pfn_start = pfn_end;
> + }
> + free_extended_page_bmap(vb, page_bmap_num);
> +}
> +
> static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
> {
> struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
> unsigned num_allocated_pages;
> + bool chunking = virtio_has_feature(vb->vdev,
> + VIRTIO_BALLOON_F_PAGE_CHUNKS);
> + unsigned long pfn_max = 0, pfn_min = ULONG_MAX;
>
> /* We can only do one array worth at a time. */
> - num = min(num, ARRAY_SIZE(vb->pfns));
> + if (!chunking)
> + num = min(num, ARRAY_SIZE(vb->pfns));
>
> mutex_lock(&vb->balloon_lock);
> for (vb->num_pfns = 0; vb->num_pfns < num;
> @@ -162,7 +418,10 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
> msleep(200);
> break;
> }
> - set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> + if (chunking)
> + update_pfn_range(vb, page, &pfn_max, &pfn_min);
> + else
> + set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
> if (!virtio_has_feature(vb->vdev,
> VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> @@ -171,8 +430,14 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
>
> num_allocated_pages = vb->num_pfns;
> /* Did we get any? */
> - if (vb->num_pfns != 0)
> - tell_host(vb, vb->inflate_vq);
> + if (vb->num_pfns != 0) {
> + if (chunking)
> + tell_host_page_chunks(vb, &vb_dev_info->pages,
> + vb->inflate_vq,
> + pfn_max, pfn_min);
> + else
> + tell_host(vb, vb->inflate_vq);
> + }
> mutex_unlock(&vb->balloon_lock);
>
> return num_allocated_pages;
> @@ -198,9 +463,13 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
> struct page *page;
> struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
> LIST_HEAD(pages);
> + bool chunking = virtio_has_feature(vb->vdev,
> + VIRTIO_BALLOON_F_PAGE_CHUNKS);
> + unsigned long pfn_max = 0, pfn_min = ULONG_MAX;
>
> - /* We can only do one array worth at a time. */
> - num = min(num, ARRAY_SIZE(vb->pfns));
> + /* Traditionally, we can only do one array worth at a time. */
> + if (!chunking)
> + num = min(num, ARRAY_SIZE(vb->pfns));
>
> mutex_lock(&vb->balloon_lock);
> /* We can't release more pages than taken */
> @@ -210,7 +479,10 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
> page = balloon_page_dequeue(vb_dev_info);
> if (!page)
> break;
> - set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> + if (chunking)
> + update_pfn_range(vb, page, &pfn_max, &pfn_min);
> + else
> + set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> list_add(&page->lru, &pages);
> vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
> }
> @@ -221,8 +493,13 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
> * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
> * is true, we *have* to do it in this order
> */
> - if (vb->num_pfns != 0)
> - tell_host(vb, vb->deflate_vq);
> + if (vb->num_pfns != 0) {
> + if (chunking)
> + tell_host_page_chunks(vb, &pages, vb->deflate_vq,
> + pfn_max, pfn_min);
> + else
> + tell_host(vb, vb->deflate_vq);
> + }
> release_pages_balloon(vb, &pages);
> mutex_unlock(&vb->balloon_lock);
> return num_freed_pages;
> @@ -442,6 +719,14 @@ static int init_vqs(struct virtio_balloon *vb)
> }
>
> #ifdef CONFIG_BALLOON_COMPACTION
> +
> +static void tell_host_one_page(struct virtio_balloon *vb,
> + struct virtqueue *vq, struct page *page)
> +{
> + add_one_chunk(vb, vq, page_to_pfn(page),
> + VIRTIO_BALLOON_PAGES_PER_PAGE);
> +}
> +
> /*
> * virtballoon_migratepage - perform the balloon page migration on behalf of
> * a compation thread. (called under page lock)
> @@ -465,6 +750,8 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
> {
> struct virtio_balloon *vb = container_of(vb_dev_info,
> struct virtio_balloon, vb_dev_info);
> + bool chunking = virtio_has_feature(vb->vdev,
> + VIRTIO_BALLOON_F_PAGE_CHUNKS);
> unsigned long flags;
>
> /*
> @@ -486,16 +773,22 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
> vb_dev_info->isolated_pages--;
> __count_vm_event(BALLOON_MIGRATE);
> spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
> - vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> - set_page_pfns(vb, vb->pfns, newpage);
> - tell_host(vb, vb->inflate_vq);
> -
> + if (chunking) {
> + tell_host_one_page(vb, vb->inflate_vq, newpage);
> + } else {
> + vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> + set_page_pfns(vb, vb->pfns, newpage);
> + tell_host(vb, vb->inflate_vq);
> + }
> /* balloon's page migration 2nd step -- deflate "page" */
> balloon_page_delete(page);
> - vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> - set_page_pfns(vb, vb->pfns, page);
> - tell_host(vb, vb->deflate_vq);
> -
> + if (chunking) {
> + tell_host_one_page(vb, vb->deflate_vq, page);
> + } else {
> + vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> + set_page_pfns(vb, vb->pfns, page);
> + tell_host(vb, vb->deflate_vq);
> + }
> mutex_unlock(&vb->balloon_lock);
>
> put_page(page); /* balloon reference */
> @@ -522,9 +815,75 @@ static struct file_system_type balloon_fs = {
>
> #endif /* CONFIG_BALLOON_COMPACTION */
>
> +static void free_page_bmap(struct virtio_balloon *vb)
> +{
> + int i;
> +
> + for (i = 0; i < VIRTIO_BALLOON_PAGE_BMAP_DEFAULT_NUM; i++) {
> + kfree(vb->page_bmap[i]);
> + vb->page_bmap[i] = NULL;
> + }
> +}
> +
> +static int balloon_page_chunk_init(struct virtio_balloon *vb)
> +{
> + int i;
> +
> + vb->balloon_page_chunk = kmalloc(sizeof(__le64) +
> + sizeof(struct virtio_balloon_page_chunk_entry) *
> + VIRTIO_BALLOON_MAX_PAGE_CHUNKS, GFP_KERNEL);
> + if (!vb->balloon_page_chunk)
> + goto err_page_chunk;
> +
> + /*
> + * The default number of page_bmaps are allocated. More may be
> + * allocated on demand.
> + */
> + for (i = 0; i < VIRTIO_BALLOON_PAGE_BMAP_DEFAULT_NUM; i++) {
> + vb->page_bmap[i] = kmalloc(VIRTIO_BALLOON_PAGE_BMAP_SIZE,
> + GFP_KERNEL);
> + if (!vb->page_bmap[i])
> + goto err_page_bmap;
> + }
> +
> + return 0;
> +err_page_bmap:
> + free_page_bmap(vb);
> + kfree(vb->balloon_page_chunk);
> + vb->balloon_page_chunk = NULL;
> +err_page_chunk:
> + __virtio_clear_bit(vb->vdev, VIRTIO_BALLOON_F_PAGE_CHUNKS);
> + dev_warn(&vb->vdev->dev, "%s: failed\n", __func__);
> + return -ENOMEM;
> +}
> +
> +static int virtballoon_validate(struct virtio_device *vdev)
> +{
> + struct virtio_balloon *vb = NULL;
> + int err;
> +
> + vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
> + if (!vb) {
> + err = -ENOMEM;
> + goto err_vb;
> + }
> +
> + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_CHUNKS)) {
> + err = balloon_page_chunk_init(vb);
> + if (err < 0)
> + goto err_page_chunk;
> + }
> +
> + return 0;
> +err_page_chunk:
> + kfree(vb);
> +err_vb:
> + return err;
> +}
> +
> static int virtballoon_probe(struct virtio_device *vdev)
> {
> - struct virtio_balloon *vb;
> + struct virtio_balloon *vb = vdev->priv;
> int err;
>
> if (!vdev->config->get) {
> @@ -533,17 +892,12 @@ static int virtballoon_probe(struct virtio_device *vdev)
> return -EINVAL;
> }
>
> - vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
> - if (!vb) {
> - err = -ENOMEM;
> - goto out;
> - }
> -
> INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
> INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
> spin_lock_init(&vb->stop_update_lock);
> vb->stop_update = false;
> vb->num_pages = 0;
> +
> mutex_init(&vb->balloon_lock);
> init_waitqueue_head(&vb->acked);
> vb->vdev = vdev;
> @@ -590,7 +944,6 @@ static int virtballoon_probe(struct virtio_device *vdev)
> vdev->config->del_vqs(vdev);
> out_free_vb:
> kfree(vb);
> -out:
> return err;
> }
>
> @@ -620,6 +973,8 @@ static void virtballoon_remove(struct virtio_device *vdev)
> cancel_work_sync(&vb->update_balloon_stats_work);
>
> remove_common(vb);
> + free_page_bmap(vb);
> + kfree(vb->balloon_page_chunk);
> #ifdef CONFIG_BALLOON_COMPACTION
> if (vb->vb_dev_info.inode)
> iput(vb->vb_dev_info.inode);
> @@ -664,6 +1019,7 @@ static unsigned int features[] = {
> VIRTIO_BALLOON_F_MUST_TELL_HOST,
> VIRTIO_BALLOON_F_STATS_VQ,
> VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
> + VIRTIO_BALLOON_F_PAGE_CHUNKS,
> };
>
> static struct virtio_driver virtio_balloon_driver = {
> @@ -674,6 +1030,7 @@ static struct virtio_driver virtio_balloon_driver = {
> .id_table = id_table,
> .probe = virtballoon_probe,
> .remove = virtballoon_remove,
> + .validate = virtballoon_validate,
> .config_changed = virtballoon_changed,
> #ifdef CONFIG_PM_SLEEP
> .freeze = virtballoon_freeze,
> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> index 343d7dd..d532ed16 100644
> --- a/include/uapi/linux/virtio_balloon.h
> +++ b/include/uapi/linux/virtio_balloon.h
> @@ -34,6 +34,7 @@
> #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_PAGE_CHUNKS 3 /* Inflate/Deflate pages in chunks */
>
> /* Size of a PFN in the balloon interface. */
> #define VIRTIO_BALLOON_PFN_SHIFT 12
> @@ -82,4 +83,17 @@ struct virtio_balloon_stat {
> __virtio64 val;
> } __attribute__((packed));
>
> +#define VIRTIO_BALLOON_CHUNK_BASE_SHIFT 12
> +#define VIRTIO_BALLOON_CHUNK_SIZE_SHIFT 12
> +struct virtio_balloon_page_chunk_entry {
> + __le64 base;
> + __le64 size;
> +};
> +
> +struct virtio_balloon_page_chunk {
> + /* Number of chunks in the payload */
> + __le64 chunk_num;
> + struct virtio_balloon_page_chunk_entry entry[];
> +};
> +
> #endif /* _LINUX_VIRTIO_BALLOON_H */
> --
> 2.7.4

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