diff mbox

[RFC,v2,kernel] balloon: speed up inflating/deflating process

Message ID 1464345250-6388-1-git-send-email-liang.z.li@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Liang Li May 27, 2016, 10:34 a.m. UTC
The implementation of the current virtio-balloon is not very efficient,
Bellow is test result of time spends on inflating the balloon to 3GB of
a 4GB idle guest:

a. allocating pages (6.5%, 103ms)
b. sending PFNs to host (68.3%, 787ms)
c. address translation (6.1%, 96ms)
d. madvise (19%, 300ms)

It takes about 1577ms for the whole inflating process to complete. The
test shows that the bottle neck is the stage b and stage d.

If using a bitmap to send the page info instead of the PFNs, we can
reduce the overhead spends on stage b quite a lot. Furthermore, it's
possible to do the address translation and do the madvise with a bulk
of pages, instead of the current page per page way, so the overhead of
stage c and stage d can also be reduced a lot.

This patch is the kernel side implementation which is intended to speed
up the inflating & deflating process by adding a new feature to the
virtio-balloon device. And now, inflating the balloon to 3GB of a 4GB
idle guest only takes 200ms, it's about 8 times as fast as before.

TODO: optimize stage a by allocating/freeing a chunk of pages instead
of a single page at a time.

v2 change:
    1. Use a small page bitmap instead of a large one.
    2. Address some of comments of v1.

Signed-off-by: Liang Li <liang.z.li@intel.com>
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Amit Shah <amit.shah@redhat.com>
---
 drivers/virtio/virtio_balloon.c     | 207 ++++++++++++++++++++++++++++++++++--
 include/uapi/linux/virtio_balloon.h |   1 +
 2 files changed, 200 insertions(+), 8 deletions(-)

Comments

Liang Li June 1, 2016, 2:40 a.m. UTC | #1
Hi MST,

About the size of page bitmap, I have test the performance of filling the balloon to 15GB with a 16GB RAM VM.

===============================
32K Byte (cover 1GB of RAM)

Time spends on inflating: 2031ms
---------------------------------------------
64K Byte (cover 2GB of RAM)

Time spends on inflating: 1507ms
--------------------------------------------
512K Byte (cover 16GB of RAM)

Time spends on inflating: 1237ms
================================

It shows the performance is better if using a larger page bitmap, should we use a 64K/ 128KB page bitmap
for a better  balance between the performance and the memory consumption?

BTW, about the VIRTIO_BALLOON_F_DEFLATE_ON_OOM feature, I found the configurable  'oom_pages' 
will be limited by the ARRAY_SIZE(vb->pfns), which means only 1MB of RAM will be recycled each time even
the users want more, is that too conservative? 

Liang


> -----Original Message-----
> From: Li, Liang Z
> Sent: Friday, May 27, 2016 6:34 PM
> To: linux-kernel@vger.kernel.org
> Cc: kvm@vger.kernel.org; qemu-devel@nongnu.org; Li, Liang Z; Michael S.
> Tsirkin; Paolo Bonzini; Cornelia Huck; Amit Shah
> Subject: [PATCH RFC v2 kernel] balloon: speed up inflating/deflating process
> 
> The implementation of the current virtio-balloon is not very efficient, Bellow
> is test result of time spends on inflating the balloon to 3GB of a 4GB idle
> guest:
> 
> a. allocating pages (6.5%, 103ms)
> b. sending PFNs to host (68.3%, 787ms)
> c. address translation (6.1%, 96ms)
> d. madvise (19%, 300ms)
> 
> It takes about 1577ms for the whole inflating process to complete. The test
> shows that the bottle neck is the stage b and stage d.
> 
> If using a bitmap to send the page info instead of the PFNs, we can reduce
> the overhead spends on stage b quite a lot. Furthermore, it's possible to do
> the address translation and do the madvise with a bulk of pages, instead of
> the current page per page way, so the overhead of stage c and stage d can
> also be reduced a lot.
> 
> This patch is the kernel side implementation which is intended to speed up
> the inflating & deflating process by adding a new feature to the virtio-balloon
> device. And now, inflating the balloon to 3GB of a 4GB idle guest only takes
> 200ms, it's about 8 times as fast as before.
> 
> TODO: optimize stage a by allocating/freeing a chunk of pages instead of a
> single page at a time.
> 
> v2 change:
>     1. Use a small page bitmap instead of a large one.
>     2. Address some of comments of v1.
> 
> Signed-off-by: Liang Li <liang.z.li@intel.com>
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> Cc: Amit Shah <amit.shah@redhat.com>
> ---
>  drivers/virtio/virtio_balloon.c     | 207
> ++++++++++++++++++++++++++++++++++--
>  include/uapi/linux/virtio_balloon.h |   1 +
>  2 files changed, 200 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 476c0e3..823b4e4 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -40,11 +40,19 @@
>  #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256  #define
> OOM_VBALLOON_DEFAULT_PAGES 256  #define
> VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
> +#define VIRTIO_BALLOON_PFNS_LIMIT ((2 * (1ULL << 30)) >> PAGE_SHIFT)
> /*
> +2GB */
> 
>  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");
> 
> +struct balloon_bmap_hdr {
> +	__virtio32 type;
> +	__virtio32 page_shift;
> +	__virtio64 start_pfn;
> +	__virtio64 bmap_len;
> +};
> +
>  struct virtio_balloon {
>  	struct virtio_device *vdev;
>  	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; @@ -62,6
> +70,13 @@ struct virtio_balloon {
> 
>  	/* Number of balloon pages we've told the Host we're not using. */
>  	unsigned int num_pages;
> +	/* Bitmap and length used to tell the host the pages */
> +	unsigned long *page_bitmap;
> +	unsigned long bmap_len;
> +	/* Used to record the processed pfn range */
> +	unsigned long min_pfn, max_pfn, start_pfn, end_pfn;
> +	/* Used for sending page bitmap and header */
> +	struct scatterlist sg[2];
>  	/*
>  	 * The pages we've told the Host we're not using are enqueued
>  	 * at vb_dev_info->pages list.
> @@ -111,15 +126,39 @@ static void balloon_ack(struct virtqueue *vq)
>  	wake_up(&vb->acked);
>  }
> 
> +static inline void init_pfn_range(struct virtio_balloon *vb) {
> +	vb->min_pfn = (1UL << 48);
> +	vb->max_pfn = 0;
> +}
> +
>  static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)  {
> -	struct scatterlist sg;
>  	unsigned int len;
> 
> -	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
> +	if (virtio_has_feature(vb->vdev,
> VIRTIO_BALLOON_F_PAGE_BITMAP)) {
> +		struct balloon_bmap_hdr hdr;
> +		unsigned long bmap_len;
> +
> +		hdr.type = cpu_to_virtio32(vb->vdev, 0);
> +		hdr.page_shift = cpu_to_virtio32(vb->vdev, PAGE_SHIFT);
> +		hdr.start_pfn = cpu_to_virtio64(vb->vdev, vb->start_pfn);
> +		bmap_len = min(vb->bmap_len,
> +                         (vb->end_pfn - vb->start_pfn) / BITS_PER_BYTE);
> +		hdr.bmap_len = cpu_to_virtio64(vb-vdev, bmap_len);
> +		sg_set_buf(&vb->sg[0], &hdr, sizeof(hdr));
> +		sg_set_buf(&vb->sg[1], vb->page_bitmap, bmap_len);
> +		virtqueue_add_outbuf(vq, vb->sg, 2, vb, GFP_KERNEL);
> +	} else {
> +		struct scatterlist sg;
> +
> +		sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb-
> >num_pfns);
> +		/* We should always be able to add one buffer to an
> +		* empty queue.
> +		*/
> +		virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> +	}
> 
> -	/* We should always be able to add one buffer to an empty queue.
> */
> -	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
>  	virtqueue_kick(vq);
> 
>  	/* When host has read buffer, this completes via balloon_ack */ @@
> -139,7 +178,18 @@ static void set_page_pfns(struct virtio_balloon *vb,
>  					  page_to_balloon_pfn(page) + i);
>  }
> 
> -static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
> +static inline void update_pfn_range(struct virtio_balloon *vb,
> +				 struct page *page)
> +{
> +	unsigned long balloon_pfn = page_to_balloon_pfn(page);
> +
> +	if (balloon_pfn < vb->min_pfn)
> +		vb->min_pfn = balloon_pfn;
> +	if (balloon_pfn > vb->max_pfn)
> +		vb->max_pfn = balloon_pfn;
> +}
> +
> +static unsigned int fill_balloon_pfns(struct virtio_balloon *vb, size_t
> +num)
>  {
>  	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
>  	unsigned num_allocated_pages;
> @@ -176,7 +226,126 @@ static unsigned fill_balloon(struct virtio_balloon *vb,
> size_t num)
>  	return num_allocated_pages;
>  }
> 
> -static void release_pages_balloon(struct virtio_balloon *vb)
> +static void tell_host_bitmap(struct virtio_balloon *vb,
> +			 struct list_head *pages, struct virtqueue *vq) {
> +	unsigned long pfn;
> +	struct page *page, *next;
> +	bool find;
> +
> +	vb->min_pfn = rounddown(vb->min_pfn, BITS_PER_LONG);
> +	vb->max_pfn = roundup(vb->max_pfn, BITS_PER_LONG);
> +	for (pfn = vb->min_pfn; pfn < vb->max_pfn;
> +			pfn += VIRTIO_BALLOON_PFNS_LIMIT) {
> +		vb->start_pfn = pfn;
> +		vb->end_pfn = pfn;
> +		memset(vb->page_bitmap, 0, vb->bmap_len);
> +		find = false;
> +		list_for_each_entry_safe(page, next, pages, lru) {
> +			unsigned long balloon_pfn =
> page_to_balloon_pfn(page);
> +
> +			if (balloon_pfn < pfn ||
> +				 balloon_pfn >= pfn +
> VIRTIO_BALLOON_PFNS_LIMIT)
> +				continue;
> +			set_bit(balloon_pfn - pfn, vb->page_bitmap);
> +			if (balloon_pfn > vb->end_pfn)
> +				vb->end_pfn = balloon_pfn;
> +			find = true;
> +		}
> +		if (find) {
> +			vb->end_pfn = roundup(vb->end_pfn,
> BITS_PER_LONG);
> +			tell_host(vb, vq);
> +		}
> +	}
> +}
> +
> +static long fill_balloon_bitmap(struct virtio_balloon *vb, size_t num)
> +{
> +	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
> +	long num_allocated_pages;
> +
> +	init_pfn_range(vb);
> +	mutex_lock(&vb->balloon_lock);
> +	for (vb->num_pfns = 0; vb->num_pfns < num;
> +		vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
> +		struct page *page = balloon_page_enqueue(vb_dev_info);
> +
> +		if (!page) {
> +			dev_info_ratelimited(&vb->vdev->dev,
> +					     "Out of puff! Can't get %u
> pages\n",
> +
> VIRTIO_BALLOON_PAGES_PER_PAGE);
> +			/* Sleep for at least 1/5 of a second before retry. */
> +			msleep(200);
> +			break;
> +		}
> +		update_pfn_range(vb, page);
> +		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
> +		if (!virtio_has_feature(vb->vdev,
> +
> 	VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> +			adjust_managed_page_count(page, -1);
> +	}
> +
> +	num_allocated_pages = vb->num_pfns;
> +	tell_host_bitmap(vb, &vb_dev_info->pages, vb->inflate_vq);
> +	mutex_unlock(&vb->balloon_lock);
> +
> +	return num_allocated_pages;
> +}
> +
> +static long fill_balloon(struct virtio_balloon *vb, size_t num) {
> +	long num_allocated_pages;
> +
> +	if (virtio_has_feature(vb->vdev,
> VIRTIO_BALLOON_F_PAGE_BITMAP))
> +		num_allocated_pages = fill_balloon_bitmap(vb, num);
> +	else
> +		num_allocated_pages = fill_balloon_pfns(vb, num);
> +
> +	return num_allocated_pages;
> +}
> +
> +static void release_pages_balloon_bitmap(struct virtio_balloon *vb,
> +				 struct list_head *pages)
> +{
> +	struct page *page, *next;
> +
> +	list_for_each_entry_safe(page, next, pages, lru) {
> +		if (!virtio_has_feature(vb->vdev,
> +			VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> +			adjust_managed_page_count(page, 1);
> +		list_del(&page->lru);
> +		put_page(page);
> +	}
> +}
> +
> +static unsigned long leak_balloon_bitmap(struct virtio_balloon *vb,
> +size_t num) {
> +	unsigned long num_freed_pages;
> +	struct page *page;
> +	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
> +	LIST_HEAD(pages);
> +
> +	init_pfn_range(vb);
> +	mutex_lock(&vb->balloon_lock);
> +	for (vb->num_pfns = 0; vb->num_pfns < num;
> +	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
> +		page = balloon_page_dequeue(vb_dev_info);
> +		if (!page)
> +			break;
> +		update_pfn_range(vb, page);
> +		list_add(&page->lru, &pages);
> +		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
> +	}
> +
> +	num_freed_pages = vb->num_pfns;
> +	tell_host_bitmap(vb, &pages, vb->deflate_vq);
> +	release_pages_balloon_bitmap(vb, &pages);
> +	mutex_unlock(&vb->balloon_lock);
> +
> +	return num_freed_pages;
> +}
> +
> +static void release_pages_balloon_pfns(struct virtio_balloon *vb)
>  {
>  	unsigned int i;
>  	struct page *page;
> @@ -192,7 +361,7 @@ static void release_pages_balloon(struct
> virtio_balloon *vb)
>  	}
>  }
> 
> -static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
> +static unsigned int leak_balloon_pfns(struct virtio_balloon *vb, size_t
> +num)
>  {
>  	unsigned num_freed_pages;
>  	struct page *page;
> @@ -219,11 +388,23 @@ static unsigned leak_balloon(struct virtio_balloon
> *vb, size_t num)
>  	 */
>  	if (vb->num_pfns != 0)
>  		tell_host(vb, vb->deflate_vq);
> -	release_pages_balloon(vb);
> +	release_pages_balloon_pfns(vb);
>  	mutex_unlock(&vb->balloon_lock);
>  	return num_freed_pages;
>  }
> 
> +static long leak_balloon(struct virtio_balloon *vb, size_t num) {
> +	long num_freed_pages;
> +
> +	if (virtio_has_feature(vb->vdev,
> VIRTIO_BALLOON_F_PAGE_BITMAP))
> +		num_freed_pages = leak_balloon_bitmap(vb, num);
> +	else
> +		num_freed_pages = leak_balloon_pfns(vb, num);
> +
> +	return num_freed_pages;
> +}
> +
>  static inline void update_stat(struct virtio_balloon *vb, int idx,
>  			       u16 tag, u64 val)
>  {
> @@ -514,6 +695,14 @@ static int virtballoon_probe(struct virtio_device
> *vdev)
>  	spin_lock_init(&vb->stop_update_lock);
>  	vb->stop_update = false;
>  	vb->num_pages = 0;
> +	vb->bmap_len = ALIGN(VIRTIO_BALLOON_PFNS_LIMIT,
> BITS_PER_LONG) /
> +		 BITS_PER_BYTE + 2 * sizeof(unsigned long);
> +	vb->page_bitmap = kzalloc(vb->bmap_len, GFP_KERNEL);
> +	if (!vb->page_bitmap) {
> +		err = -ENOMEM;
> +		goto out;
> +	}
> +	sg_init_table(vb->sg, 2);
>  	mutex_init(&vb->balloon_lock);
>  	init_waitqueue_head(&vb->acked);
>  	vb->vdev = vdev;
> @@ -571,6 +760,7 @@ static void virtballoon_remove(struct virtio_device
> *vdev)
>  	cancel_work_sync(&vb->update_balloon_stats_work);
> 
>  	remove_common(vb);
> +	kfree(vb->page_bitmap);
>  	kfree(vb);
>  }
> 
> @@ -609,6 +799,7 @@ 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_BITMAP,
>  };
> 
>  static struct virtio_driver virtio_balloon_driver = { diff --git
> a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> index 343d7dd..f78fa47 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_BITMAP	3 /* Send page info with
> bitmap */
> 
>  /* Size of a PFN in the balloon interface. */  #define
> VIRTIO_BALLOON_PFN_SHIFT 12
> --
> 1.9.1

--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Liang Li June 7, 2016, 9:26 a.m. UTC | #2
Ping...

Liang


> -----Original Message-----
> From: Li, Liang Z
> Sent: Wednesday, June 01, 2016 10:41 AM
> To: linux-kernel@vger.kernel.org
> Cc: kvm@vger.kernel.org; qemu-devel@nongnu.org; Michael S. Tsirkin;
> Paolo Bonzini; Cornelia Huck; Amit Shah
> Subject: RE: [PATCH RFC v2 kernel] balloon: speed up inflating/deflating
> process
> 
> Hi MST,
> 
> About the size of page bitmap, I have test the performance of filling the
> balloon to 15GB with a 16GB RAM VM.
> 
> ===============================
> 32K Byte (cover 1GB of RAM)
> 
> Time spends on inflating: 2031ms
> ---------------------------------------------
> 64K Byte (cover 2GB of RAM)
> 
> Time spends on inflating: 1507ms
> --------------------------------------------
> 512K Byte (cover 16GB of RAM)
> 
> Time spends on inflating: 1237ms
> ================================
> 
> It shows the performance is better if using a larger page bitmap, should we
> use a 64K/ 128KB page bitmap for a better  balance between the
> performance and the memory consumption?
> 
> BTW, about the VIRTIO_BALLOON_F_DEFLATE_ON_OOM feature, I found
> the configurable  'oom_pages'
> will be limited by the ARRAY_SIZE(vb->pfns), which means only 1MB of RAM
> will be recycled each time even the users want more, is that too conservative?
> 
> Liang
> 
> 
> > -----Original Message-----
> > From: Li, Liang Z
> > Sent: Friday, May 27, 2016 6:34 PM
> > To: linux-kernel@vger.kernel.org
> > Cc: kvm@vger.kernel.org; qemu-devel@nongnu.org; Li, Liang Z; Michael S.
> > Tsirkin; Paolo Bonzini; Cornelia Huck; Amit Shah
> > Subject: [PATCH RFC v2 kernel] balloon: speed up inflating/deflating
> > process
> >
> > The implementation of the current virtio-balloon is not very
> > efficient, Bellow is test result of time spends on inflating the
> > balloon to 3GB of a 4GB idle
> > guest:
> >
> > a. allocating pages (6.5%, 103ms)
> > b. sending PFNs to host (68.3%, 787ms) c. address translation (6.1%,
> > 96ms) d. madvise (19%, 300ms)
> >
> > It takes about 1577ms for the whole inflating process to complete. The
> > test shows that the bottle neck is the stage b and stage d.
> >
> > If using a bitmap to send the page info instead of the PFNs, we can
> > reduce the overhead spends on stage b quite a lot. Furthermore, it's
> > possible to do the address translation and do the madvise with a bulk
> > of pages, instead of the current page per page way, so the overhead of
> > stage c and stage d can also be reduced a lot.
> >
> > This patch is the kernel side implementation which is intended to
> > speed up the inflating & deflating process by adding a new feature to
> > the virtio-balloon device. And now, inflating the balloon to 3GB of a
> > 4GB idle guest only takes 200ms, it's about 8 times as fast as before.
> >
> > TODO: optimize stage a by allocating/freeing a chunk of pages instead
> > of a single page at a time.
> >
> > v2 change:
> >     1. Use a small page bitmap instead of a large one.
> >     2. Address some of comments of v1.
> >
> > Signed-off-by: Liang Li <liang.z.li@intel.com>
> > Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> > Cc: Amit Shah <amit.shah@redhat.com>
> > ---
> >  drivers/virtio/virtio_balloon.c     | 207
> > ++++++++++++++++++++++++++++++++++--
> >  include/uapi/linux/virtio_balloon.h |   1 +
> >  2 files changed, 200 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_balloon.c
> > b/drivers/virtio/virtio_balloon.c index 476c0e3..823b4e4 100644
> > --- a/drivers/virtio/virtio_balloon.c
> > +++ b/drivers/virtio/virtio_balloon.c
> > @@ -40,11 +40,19 @@
> >  #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256  #define
> > OOM_VBALLOON_DEFAULT_PAGES 256  #define
> > VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
> > +#define VIRTIO_BALLOON_PFNS_LIMIT ((2 * (1ULL << 30)) >>
> PAGE_SHIFT)
> > /*
> > +2GB */
> >
> >  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");
> >
> > +struct balloon_bmap_hdr {
> > +	__virtio32 type;
> > +	__virtio32 page_shift;
> > +	__virtio64 start_pfn;
> > +	__virtio64 bmap_len;
> > +};
> > +
> >  struct virtio_balloon {
> >  	struct virtio_device *vdev;
> >  	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; @@ -62,6
> > +70,13 @@ struct virtio_balloon {
> >
> >  	/* Number of balloon pages we've told the Host we're not using. */
> >  	unsigned int num_pages;
> > +	/* Bitmap and length used to tell the host the pages */
> > +	unsigned long *page_bitmap;
> > +	unsigned long bmap_len;
> > +	/* Used to record the processed pfn range */
> > +	unsigned long min_pfn, max_pfn, start_pfn, end_pfn;
> > +	/* Used for sending page bitmap and header */
> > +	struct scatterlist sg[2];
> >  	/*
> >  	 * The pages we've told the Host we're not using are enqueued
> >  	 * at vb_dev_info->pages list.
> > @@ -111,15 +126,39 @@ static void balloon_ack(struct virtqueue *vq)
> >  	wake_up(&vb->acked);
> >  }
> >
> > +static inline void init_pfn_range(struct virtio_balloon *vb) {
> > +	vb->min_pfn = (1UL << 48);
> > +	vb->max_pfn = 0;
> > +}
> > +
> >  static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)  {
> > -	struct scatterlist sg;
> >  	unsigned int len;
> >
> > -	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
> > +	if (virtio_has_feature(vb->vdev,
> > VIRTIO_BALLOON_F_PAGE_BITMAP)) {
> > +		struct balloon_bmap_hdr hdr;
> > +		unsigned long bmap_len;
> > +
> > +		hdr.type = cpu_to_virtio32(vb->vdev, 0);
> > +		hdr.page_shift = cpu_to_virtio32(vb->vdev, PAGE_SHIFT);
> > +		hdr.start_pfn = cpu_to_virtio64(vb->vdev, vb->start_pfn);
> > +		bmap_len = min(vb->bmap_len,
> > +                         (vb->end_pfn - vb->start_pfn) / BITS_PER_BYTE);
> > +		hdr.bmap_len = cpu_to_virtio64(vb-vdev, bmap_len);
> > +		sg_set_buf(&vb->sg[0], &hdr, sizeof(hdr));
> > +		sg_set_buf(&vb->sg[1], vb->page_bitmap, bmap_len);
> > +		virtqueue_add_outbuf(vq, vb->sg, 2, vb, GFP_KERNEL);
> > +	} else {
> > +		struct scatterlist sg;
> > +
> > +		sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb-
> > >num_pfns);
> > +		/* We should always be able to add one buffer to an
> > +		* empty queue.
> > +		*/
> > +		virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> > +	}
> >
> > -	/* We should always be able to add one buffer to an empty queue.
> > */
> > -	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> >  	virtqueue_kick(vq);
> >
> >  	/* When host has read buffer, this completes via balloon_ack */ @@
> > -139,7 +178,18 @@ static void set_page_pfns(struct virtio_balloon *vb,
> >  					  page_to_balloon_pfn(page) + i);  }
> >
> > -static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
> > +static inline void update_pfn_range(struct virtio_balloon *vb,
> > +				 struct page *page)
> > +{
> > +	unsigned long balloon_pfn = page_to_balloon_pfn(page);
> > +
> > +	if (balloon_pfn < vb->min_pfn)
> > +		vb->min_pfn = balloon_pfn;
> > +	if (balloon_pfn > vb->max_pfn)
> > +		vb->max_pfn = balloon_pfn;
> > +}
> > +
> > +static unsigned int fill_balloon_pfns(struct virtio_balloon *vb,
> > +size_t
> > +num)
> >  {
> >  	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
> >  	unsigned num_allocated_pages;
> > @@ -176,7 +226,126 @@ static unsigned fill_balloon(struct
> > virtio_balloon *vb, size_t num)
> >  	return num_allocated_pages;
> >  }
> >
> > -static void release_pages_balloon(struct virtio_balloon *vb)
> > +static void tell_host_bitmap(struct virtio_balloon *vb,
> > +			 struct list_head *pages, struct virtqueue *vq) {
> > +	unsigned long pfn;
> > +	struct page *page, *next;
> > +	bool find;
> > +
> > +	vb->min_pfn = rounddown(vb->min_pfn, BITS_PER_LONG);
> > +	vb->max_pfn = roundup(vb->max_pfn, BITS_PER_LONG);
> > +	for (pfn = vb->min_pfn; pfn < vb->max_pfn;
> > +			pfn += VIRTIO_BALLOON_PFNS_LIMIT) {
> > +		vb->start_pfn = pfn;
> > +		vb->end_pfn = pfn;
> > +		memset(vb->page_bitmap, 0, vb->bmap_len);
> > +		find = false;
> > +		list_for_each_entry_safe(page, next, pages, lru) {
> > +			unsigned long balloon_pfn =
> > page_to_balloon_pfn(page);
> > +
> > +			if (balloon_pfn < pfn ||
> > +				 balloon_pfn >= pfn +
> > VIRTIO_BALLOON_PFNS_LIMIT)
> > +				continue;
> > +			set_bit(balloon_pfn - pfn, vb->page_bitmap);
> > +			if (balloon_pfn > vb->end_pfn)
> > +				vb->end_pfn = balloon_pfn;
> > +			find = true;
> > +		}
> > +		if (find) {
> > +			vb->end_pfn = roundup(vb->end_pfn,
> > BITS_PER_LONG);
> > +			tell_host(vb, vq);
> > +		}
> > +	}
> > +}
> > +
> > +static long fill_balloon_bitmap(struct virtio_balloon *vb, size_t
> > +num) {
> > +	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
> > +	long num_allocated_pages;
> > +
> > +	init_pfn_range(vb);
> > +	mutex_lock(&vb->balloon_lock);
> > +	for (vb->num_pfns = 0; vb->num_pfns < num;
> > +		vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
> > +		struct page *page = balloon_page_enqueue(vb_dev_info);
> > +
> > +		if (!page) {
> > +			dev_info_ratelimited(&vb->vdev->dev,
> > +					     "Out of puff! Can't get %u
> > pages\n",
> > +
> > VIRTIO_BALLOON_PAGES_PER_PAGE);
> > +			/* Sleep for at least 1/5 of a second before retry. */
> > +			msleep(200);
> > +			break;
> > +		}
> > +		update_pfn_range(vb, page);
> > +		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
> > +		if (!virtio_has_feature(vb->vdev,
> > +
> > 	VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> > +			adjust_managed_page_count(page, -1);
> > +	}
> > +
> > +	num_allocated_pages = vb->num_pfns;
> > +	tell_host_bitmap(vb, &vb_dev_info->pages, vb->inflate_vq);
> > +	mutex_unlock(&vb->balloon_lock);
> > +
> > +	return num_allocated_pages;
> > +}
> > +
> > +static long fill_balloon(struct virtio_balloon *vb, size_t num) {
> > +	long num_allocated_pages;
> > +
> > +	if (virtio_has_feature(vb->vdev,
> > VIRTIO_BALLOON_F_PAGE_BITMAP))
> > +		num_allocated_pages = fill_balloon_bitmap(vb, num);
> > +	else
> > +		num_allocated_pages = fill_balloon_pfns(vb, num);
> > +
> > +	return num_allocated_pages;
> > +}
> > +
> > +static void release_pages_balloon_bitmap(struct virtio_balloon *vb,
> > +				 struct list_head *pages)
> > +{
> > +	struct page *page, *next;
> > +
> > +	list_for_each_entry_safe(page, next, pages, lru) {
> > +		if (!virtio_has_feature(vb->vdev,
> > +			VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> > +			adjust_managed_page_count(page, 1);
> > +		list_del(&page->lru);
> > +		put_page(page);
> > +	}
> > +}
> > +
> > +static unsigned long leak_balloon_bitmap(struct virtio_balloon *vb,
> > +size_t num) {
> > +	unsigned long num_freed_pages;
> > +	struct page *page;
> > +	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
> > +	LIST_HEAD(pages);
> > +
> > +	init_pfn_range(vb);
> > +	mutex_lock(&vb->balloon_lock);
> > +	for (vb->num_pfns = 0; vb->num_pfns < num;
> > +	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
> > +		page = balloon_page_dequeue(vb_dev_info);
> > +		if (!page)
> > +			break;
> > +		update_pfn_range(vb, page);
> > +		list_add(&page->lru, &pages);
> > +		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
> > +	}
> > +
> > +	num_freed_pages = vb->num_pfns;
> > +	tell_host_bitmap(vb, &pages, vb->deflate_vq);
> > +	release_pages_balloon_bitmap(vb, &pages);
> > +	mutex_unlock(&vb->balloon_lock);
> > +
> > +	return num_freed_pages;
> > +}
> > +
> > +static void release_pages_balloon_pfns(struct virtio_balloon *vb)
> >  {
> >  	unsigned int i;
> >  	struct page *page;
> > @@ -192,7 +361,7 @@ static void release_pages_balloon(struct
> > virtio_balloon *vb)
> >  	}
> >  }
> >
> > -static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
> > +static unsigned int leak_balloon_pfns(struct virtio_balloon *vb,
> > +size_t
> > +num)
> >  {
> >  	unsigned num_freed_pages;
> >  	struct page *page;
> > @@ -219,11 +388,23 @@ static unsigned leak_balloon(struct
> > virtio_balloon *vb, size_t num)
> >  	 */
> >  	if (vb->num_pfns != 0)
> >  		tell_host(vb, vb->deflate_vq);
> > -	release_pages_balloon(vb);
> > +	release_pages_balloon_pfns(vb);
> >  	mutex_unlock(&vb->balloon_lock);
> >  	return num_freed_pages;
> >  }
> >
> > +static long leak_balloon(struct virtio_balloon *vb, size_t num) {
> > +	long num_freed_pages;
> > +
> > +	if (virtio_has_feature(vb->vdev,
> > VIRTIO_BALLOON_F_PAGE_BITMAP))
> > +		num_freed_pages = leak_balloon_bitmap(vb, num);
> > +	else
> > +		num_freed_pages = leak_balloon_pfns(vb, num);
> > +
> > +	return num_freed_pages;
> > +}
> > +
> >  static inline void update_stat(struct virtio_balloon *vb, int idx,
> >  			       u16 tag, u64 val)
> >  {
> > @@ -514,6 +695,14 @@ static int virtballoon_probe(struct virtio_device
> > *vdev)
> >  	spin_lock_init(&vb->stop_update_lock);
> >  	vb->stop_update = false;
> >  	vb->num_pages = 0;
> > +	vb->bmap_len = ALIGN(VIRTIO_BALLOON_PFNS_LIMIT,
> > BITS_PER_LONG) /
> > +		 BITS_PER_BYTE + 2 * sizeof(unsigned long);
> > +	vb->page_bitmap = kzalloc(vb->bmap_len, GFP_KERNEL);
> > +	if (!vb->page_bitmap) {
> > +		err = -ENOMEM;
> > +		goto out;
> > +	}
> > +	sg_init_table(vb->sg, 2);
> >  	mutex_init(&vb->balloon_lock);
> >  	init_waitqueue_head(&vb->acked);
> >  	vb->vdev = vdev;
> > @@ -571,6 +760,7 @@ static void virtballoon_remove(struct
> > virtio_device
> > *vdev)
> >  	cancel_work_sync(&vb->update_balloon_stats_work);
> >
> >  	remove_common(vb);
> > +	kfree(vb->page_bitmap);
> >  	kfree(vb);
> >  }
> >
> > @@ -609,6 +799,7 @@ 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_BITMAP,
> >  };
> >
> >  static struct virtio_driver virtio_balloon_driver = { diff --git
> > a/include/uapi/linux/virtio_balloon.h
> > b/include/uapi/linux/virtio_balloon.h
> > index 343d7dd..f78fa47 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_BITMAP	3 /* Send page info
> with
> > bitmap */
> >
> >  /* Size of a PFN in the balloon interface. */  #define
> > VIRTIO_BALLOON_PFN_SHIFT 12
> > --
> > 1.9.1

--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 476c0e3..823b4e4 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -40,11 +40,19 @@ 
 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
 #define OOM_VBALLOON_DEFAULT_PAGES 256
 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
+#define VIRTIO_BALLOON_PFNS_LIMIT ((2 * (1ULL << 30)) >> PAGE_SHIFT) /* 2GB */
 
 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");
 
+struct balloon_bmap_hdr {
+	__virtio32 type;
+	__virtio32 page_shift;
+	__virtio64 start_pfn;
+	__virtio64 bmap_len;
+};
+
 struct virtio_balloon {
 	struct virtio_device *vdev;
 	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
@@ -62,6 +70,13 @@  struct virtio_balloon {
 
 	/* Number of balloon pages we've told the Host we're not using. */
 	unsigned int num_pages;
+	/* Bitmap and length used to tell the host the pages */
+	unsigned long *page_bitmap;
+	unsigned long bmap_len;
+	/* Used to record the processed pfn range */
+	unsigned long min_pfn, max_pfn, start_pfn, end_pfn;
+	/* Used for sending page bitmap and header */
+	struct scatterlist sg[2];
 	/*
 	 * The pages we've told the Host we're not using are enqueued
 	 * at vb_dev_info->pages list.
@@ -111,15 +126,39 @@  static void balloon_ack(struct virtqueue *vq)
 	wake_up(&vb->acked);
 }
 
+static inline void init_pfn_range(struct virtio_balloon *vb)
+{
+	vb->min_pfn = (1UL << 48);
+	vb->max_pfn = 0;
+}
+
 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 {
-	struct scatterlist sg;
 	unsigned int len;
 
-	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_PAGE_BITMAP)) {
+		struct balloon_bmap_hdr hdr;
+		unsigned long bmap_len;
+
+		hdr.type = cpu_to_virtio32(vb->vdev, 0);
+		hdr.page_shift = cpu_to_virtio32(vb->vdev, PAGE_SHIFT);
+		hdr.start_pfn = cpu_to_virtio64(vb->vdev, vb->start_pfn);
+		bmap_len = min(vb->bmap_len,
+                         (vb->end_pfn - vb->start_pfn) / BITS_PER_BYTE);
+		hdr.bmap_len = cpu_to_virtio64(vb-vdev, bmap_len);
+		sg_set_buf(&vb->sg[0], &hdr, sizeof(hdr));
+		sg_set_buf(&vb->sg[1], vb->page_bitmap, bmap_len);
+		virtqueue_add_outbuf(vq, vb->sg, 2, vb, GFP_KERNEL);
+	} else {
+		struct scatterlist sg;
+
+		sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
+		/* We should always be able to add one buffer to an
+		* empty queue.
+		*/
+		virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
+	}
 
-	/* We should always be able to add one buffer to an empty queue. */
-	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 	virtqueue_kick(vq);
 
 	/* When host has read buffer, this completes via balloon_ack */
@@ -139,7 +178,18 @@  static void set_page_pfns(struct virtio_balloon *vb,
 					  page_to_balloon_pfn(page) + i);
 }
 
-static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
+static inline void update_pfn_range(struct virtio_balloon *vb,
+				 struct page *page)
+{
+	unsigned long balloon_pfn = page_to_balloon_pfn(page);
+
+	if (balloon_pfn < vb->min_pfn)
+		vb->min_pfn = balloon_pfn;
+	if (balloon_pfn > vb->max_pfn)
+		vb->max_pfn = balloon_pfn;
+}
+
+static unsigned int fill_balloon_pfns(struct virtio_balloon *vb, size_t num)
 {
 	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 	unsigned num_allocated_pages;
@@ -176,7 +226,126 @@  static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 	return num_allocated_pages;
 }
 
-static void release_pages_balloon(struct virtio_balloon *vb)
+static void tell_host_bitmap(struct virtio_balloon *vb,
+			 struct list_head *pages, struct virtqueue *vq)
+{
+	unsigned long pfn;
+	struct page *page, *next;
+	bool find;
+
+	vb->min_pfn = rounddown(vb->min_pfn, BITS_PER_LONG);
+	vb->max_pfn = roundup(vb->max_pfn, BITS_PER_LONG);
+	for (pfn = vb->min_pfn; pfn < vb->max_pfn;
+			pfn += VIRTIO_BALLOON_PFNS_LIMIT) {
+		vb->start_pfn = pfn;
+		vb->end_pfn = pfn;
+		memset(vb->page_bitmap, 0, vb->bmap_len);
+		find = false;
+		list_for_each_entry_safe(page, next, pages, lru) {
+			unsigned long balloon_pfn = page_to_balloon_pfn(page);
+
+			if (balloon_pfn < pfn ||
+				 balloon_pfn >= pfn + VIRTIO_BALLOON_PFNS_LIMIT)
+				continue;
+			set_bit(balloon_pfn - pfn, vb->page_bitmap);
+			if (balloon_pfn > vb->end_pfn)
+				vb->end_pfn = balloon_pfn;
+			find = true;
+		}
+		if (find) {
+			vb->end_pfn = roundup(vb->end_pfn, BITS_PER_LONG);
+			tell_host(vb, vq);
+		}
+	}
+}
+
+static long fill_balloon_bitmap(struct virtio_balloon *vb, size_t num)
+{
+	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
+	long num_allocated_pages;
+
+	init_pfn_range(vb);
+	mutex_lock(&vb->balloon_lock);
+	for (vb->num_pfns = 0; vb->num_pfns < num;
+		vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
+		struct page *page = balloon_page_enqueue(vb_dev_info);
+
+		if (!page) {
+			dev_info_ratelimited(&vb->vdev->dev,
+					     "Out of puff! Can't get %u pages\n",
+					     VIRTIO_BALLOON_PAGES_PER_PAGE);
+			/* Sleep for at least 1/5 of a second before retry. */
+			msleep(200);
+			break;
+		}
+		update_pfn_range(vb, page);
+		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
+		if (!virtio_has_feature(vb->vdev,
+					VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+			adjust_managed_page_count(page, -1);
+	}
+
+	num_allocated_pages = vb->num_pfns;
+	tell_host_bitmap(vb, &vb_dev_info->pages, vb->inflate_vq);
+	mutex_unlock(&vb->balloon_lock);
+
+	return num_allocated_pages;
+}
+
+static long fill_balloon(struct virtio_balloon *vb, size_t num)
+{
+	long num_allocated_pages;
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_PAGE_BITMAP))
+		num_allocated_pages = fill_balloon_bitmap(vb, num);
+	else
+		num_allocated_pages = fill_balloon_pfns(vb, num);
+
+	return num_allocated_pages;
+}
+
+static void release_pages_balloon_bitmap(struct virtio_balloon *vb,
+				 struct list_head *pages)
+{
+	struct page *page, *next;
+
+	list_for_each_entry_safe(page, next, pages, lru) {
+		if (!virtio_has_feature(vb->vdev,
+			VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+			adjust_managed_page_count(page, 1);
+		list_del(&page->lru);
+		put_page(page);
+	}
+}
+
+static unsigned long leak_balloon_bitmap(struct virtio_balloon *vb, size_t num)
+{
+	unsigned long num_freed_pages;
+	struct page *page;
+	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
+	LIST_HEAD(pages);
+
+	init_pfn_range(vb);
+	mutex_lock(&vb->balloon_lock);
+	for (vb->num_pfns = 0; vb->num_pfns < num;
+	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
+		page = balloon_page_dequeue(vb_dev_info);
+		if (!page)
+			break;
+		update_pfn_range(vb, page);
+		list_add(&page->lru, &pages);
+		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
+	}
+
+	num_freed_pages = vb->num_pfns;
+	tell_host_bitmap(vb, &pages, vb->deflate_vq);
+	release_pages_balloon_bitmap(vb, &pages);
+	mutex_unlock(&vb->balloon_lock);
+
+	return num_freed_pages;
+}
+
+static void release_pages_balloon_pfns(struct virtio_balloon *vb)
 {
 	unsigned int i;
 	struct page *page;
@@ -192,7 +361,7 @@  static void release_pages_balloon(struct virtio_balloon *vb)
 	}
 }
 
-static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
+static unsigned int leak_balloon_pfns(struct virtio_balloon *vb, size_t num)
 {
 	unsigned num_freed_pages;
 	struct page *page;
@@ -219,11 +388,23 @@  static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 	 */
 	if (vb->num_pfns != 0)
 		tell_host(vb, vb->deflate_vq);
-	release_pages_balloon(vb);
+	release_pages_balloon_pfns(vb);
 	mutex_unlock(&vb->balloon_lock);
 	return num_freed_pages;
 }
 
+static long leak_balloon(struct virtio_balloon *vb, size_t num)
+{
+	long num_freed_pages;
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_PAGE_BITMAP))
+		num_freed_pages = leak_balloon_bitmap(vb, num);
+	else
+		num_freed_pages = leak_balloon_pfns(vb, num);
+
+	return num_freed_pages;
+}
+
 static inline void update_stat(struct virtio_balloon *vb, int idx,
 			       u16 tag, u64 val)
 {
@@ -514,6 +695,14 @@  static int virtballoon_probe(struct virtio_device *vdev)
 	spin_lock_init(&vb->stop_update_lock);
 	vb->stop_update = false;
 	vb->num_pages = 0;
+	vb->bmap_len = ALIGN(VIRTIO_BALLOON_PFNS_LIMIT, BITS_PER_LONG) /
+		 BITS_PER_BYTE + 2 * sizeof(unsigned long);
+	vb->page_bitmap = kzalloc(vb->bmap_len, GFP_KERNEL);
+	if (!vb->page_bitmap) {
+		err = -ENOMEM;
+		goto out;
+	}
+	sg_init_table(vb->sg, 2);
 	mutex_init(&vb->balloon_lock);
 	init_waitqueue_head(&vb->acked);
 	vb->vdev = vdev;
@@ -571,6 +760,7 @@  static void virtballoon_remove(struct virtio_device *vdev)
 	cancel_work_sync(&vb->update_balloon_stats_work);
 
 	remove_common(vb);
+	kfree(vb->page_bitmap);
 	kfree(vb);
 }
 
@@ -609,6 +799,7 @@  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_BITMAP,
 };
 
 static struct virtio_driver virtio_balloon_driver = {
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index 343d7dd..f78fa47 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_BITMAP	3 /* Send page info with bitmap */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12