This patch set contains two parts of changes to the virtio-balloon.
One is the change for speeding up the inflating & deflating process,
the main idea of this optimization is to use {pfn|length} to present
the page information instead of the PFNs, to reduce the overhead of
virtio data transmission, address translation and madvise(). This can
help to improve the performance by about 85%.
Another change is for speeding up live migration. By skipping process
guest's unused pages in the first round of data copy, to reduce needless
data processing, this can help to save quite a lot of CPU cycles and
network bandwidth. We put guest's unused page information in a
{pfn|length} array and send it to host with the virt queue of
virtio-balloon. For an idle guest with 8GB RAM, this can help to shorten
the total live migration time from 2Sec to about 500ms in 10Gbps network
environment. For an guest with quite a lot of page cache and with little
unused pages, it's possible to let the guest drop it's page cache before
live migration, this case can benefit from this new feature too.
Changes from v5 to v6:
* Drop the bitmap from the virtio ABI, use {pfn|length} only.
* Enhance the API to get the unused page information from mm.
Changes from v4 to v5:
* Drop the code to get the max_pfn, use another way instead.
* Simplify the API to get the unused page information from mm.
Changes from v3 to v4:
* Use the new scheme suggested by Dave Hansen to encode the bitmap.
* Add code which is missed in v3 to handle migrate page.
* Free the memory for bitmap intime once the operation is done.
* Address some of the comments in v3.
Changes from v2 to v3:
* Change the name of 'free page' to 'unused page'.
* Use the scatter & gather bitmap instead of a 1MB page bitmap.
* Fix overwriting the page bitmap after kicking.
* Some of MST's comments for v2.
Changes from v1 to v2:
* Abandon the patch for dropping page cache.
* Put some structures to uapi head file.
* Use a new way to determine the page bitmap size.
* Use a unified way to send the free page information with the bitmap
* Address the issues referred in MST's comments
Liang Li (5):
virtio-balloon: rework deflate to add page to a list
virtio-balloon: define new feature bit and head struct
virtio-balloon: speed up inflate/deflate process
virtio-balloon: define flags and head for host request vq
virtio-balloon: tell host vm's unused page info
drivers/virtio/virtio_balloon.c | 510 ++++++++++++++++++++++++++++++++----
include/linux/mm.h | 3 +
include/uapi/linux/virtio_balloon.h | 34 +++
mm/page_alloc.c | 120 +++++++++
4 files changed, 621 insertions(+), 46 deletions(-)
--
1.9.1
When doing the inflating/deflating operation, the current virtio-balloon
implementation uses an array to save 256 PFNS, then send these PFNS to
host through virtio and process each PFN one by one. This way is not
efficient when inflating/deflating a large mount of memory because too
many times of the following operations:
1. Virtio data transmission
2. Page allocate/free
3. Address translation(GPA->HVA)
4. madvise
The over head of these operations will consume a lot of CPU cycles and
will take a long time to complete, it may impact the QoS of the guest as
well as the host. The overhead will be reduced a lot if batch processing
is used. E.g. If there are several pages whose address are physical
contiguous in the guest, these bulk pages can be processed in one
operation.
The main idea for the optimization is to reduce the above operations as
much as possible. And it can be achieved by using a {pfn|length} array
instead of a PFN array. Comparing with PFN array, {pfn|length} array can
present more pages and is fit for batch processing.
This patch saves the deflated pages to a list instead of the PFN array,
which will allow faster notifications using the {pfn|length} down the
road. balloon_pfn_to_page() can be removed because it's useless.
Signed-off-by: Liang Li <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Cornelia Huck <[email protected]>
Cc: Amit Shah <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Hildenbrand <[email protected]>
---
drivers/virtio/virtio_balloon.c | 22 ++++++++--------------
1 file changed, 8 insertions(+), 14 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 181793f..f59cb4f 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -103,12 +103,6 @@ static u32 page_to_balloon_pfn(struct page *page)
return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
}
-static struct page *balloon_pfn_to_page(u32 pfn)
-{
- BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
- return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
-}
-
static void balloon_ack(struct virtqueue *vq)
{
struct virtio_balloon *vb = vq->vdev->priv;
@@ -181,18 +175,16 @@ 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 release_pages_balloon(struct virtio_balloon *vb,
+ struct list_head *pages)
{
- unsigned int i;
- struct page *page;
+ struct page *page, *next;
- /* Find pfns pointing at start of each page, get pages and free them. */
- for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
- page = balloon_pfn_to_page(virtio32_to_cpu(vb->vdev,
- vb->pfns[i]));
+ 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); /* balloon reference */
}
}
@@ -202,6 +194,7 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
unsigned num_freed_pages;
struct page *page;
struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
+ LIST_HEAD(pages);
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
@@ -215,6 +208,7 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
if (!page)
break;
set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
+ list_add(&page->lru, &pages);
vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
}
@@ -226,7 +220,7 @@ 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(vb, &pages);
mutex_unlock(&vb->balloon_lock);
return num_freed_pages;
}
--
1.9.1
The implementation of the current virtio-balloon is not very
efficient, the time spends on different stages of inflating
the balloon to 7GB of a 8GB idle guest:
a. allocating pages (6.5%)
b. sending PFNs to host (68.3%)
c. address translation (6.1%)
d. madvise (19%)
It takes about 4126ms for the inflating process to complete.
Debugging shows that the bottle neck are the stage b and stage d.
If using {pfn|length} array to send the page info instead of the
PFNs, we can reduce the overhead in stage b quite a lot.
Furthermore, we can do the address translation and call madvise()
with a range of memory, instead of the current page per page way,
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. With this new feature, inflating the
balloon to 7GB of a 8GB idle guest only takes 590ms, the
performance improvement is about 85%.
TODO: optimize stage a by allocating/freeing a chunk of pages
instead of a single page at a time.
Signed-off-by: Liang Li <[email protected]>
Suggested-by: Michael S. Tsirkin <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Cornelia Huck <[email protected]>
Cc: Amit Shah <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Hildenbrand <[email protected]>
---
drivers/virtio/virtio_balloon.c | 348 ++++++++++++++++++++++++++++++++++++----
1 file changed, 320 insertions(+), 28 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index f59cb4f..03383b3 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -42,6 +42,10 @@
#define OOM_VBALLOON_DEFAULT_PAGES 256
#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
+#define BALLOON_BMAP_SIZE (8 * PAGE_SIZE)
+#define PFNS_PER_BMAP (BALLOON_BMAP_SIZE * BITS_PER_BYTE)
+#define BALLOON_BMAP_COUNT 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");
@@ -67,6 +71,20 @@ struct virtio_balloon {
/* Number of balloon pages we've told the Host we're not using. */
unsigned int num_pages;
+ /* Pointer to the response header. */
+ void *resp_hdr;
+ /* Pointer to the start address of response data. */
+ __le64 *resp_data;
+ /* Size of response data buffer. */
+ unsigned int resp_buf_size;
+ /* Pointer offset of the response data. */
+ unsigned int resp_pos;
+ /* Bitmap used to save the pfns info */
+ unsigned long *page_bitmap[BALLOON_BMAP_COUNT];
+ /* Number of split page bitmaps */
+ unsigned int nr_page_bmap;
+ /* Used to record the processed pfn range */
+ unsigned long min_pfn, max_pfn, start_pfn, end_pfn;
/*
* The pages we've told the Host we're not using are enqueued
* at vb_dev_info->pages list.
@@ -110,20 +128,180 @@ static void balloon_ack(struct virtqueue *vq)
wake_up(&vb->acked);
}
-static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
+static inline void init_bmap_pfn_range(struct virtio_balloon *vb)
{
- struct scatterlist sg;
+ vb->min_pfn = ULONG_MAX;
+ vb->max_pfn = 0;
+}
+
+static inline void update_bmap_pfn_range(struct virtio_balloon *vb,
+ struct page *page)
+{
+ unsigned long balloon_pfn = page_to_balloon_pfn(page);
+
+ vb->min_pfn = min(balloon_pfn, vb->min_pfn);
+ vb->max_pfn = max(balloon_pfn, vb->max_pfn);
+}
+
+static void extend_page_bitmap(struct virtio_balloon *vb,
+ unsigned long nr_pfn)
+{
+ int i, bmap_count;
+ unsigned long bmap_len;
+
+ bmap_len = ALIGN(nr_pfn, BITS_PER_LONG) / BITS_PER_BYTE;
+ bmap_len = ALIGN(bmap_len, BALLOON_BMAP_SIZE);
+ bmap_count = min((int)(bmap_len / BALLOON_BMAP_SIZE),
+ BALLOON_BMAP_COUNT);
+
+ for (i = 1; i < bmap_count; i++) {
+ vb->page_bitmap[i] = kmalloc(BALLOON_BMAP_SIZE, GFP_KERNEL);
+ if (vb->page_bitmap[i])
+ vb->nr_page_bmap++;
+ else
+ break;
+ }
+}
+
+static void free_extended_page_bitmap(struct virtio_balloon *vb)
+{
+ int i, bmap_count = vb->nr_page_bmap;
+
+ for (i = 1; i < bmap_count; i++) {
+ kfree(vb->page_bitmap[i]);
+ vb->page_bitmap[i] = NULL;
+ vb->nr_page_bmap--;
+ }
+}
+
+static void kfree_page_bitmap(struct virtio_balloon *vb)
+{
+ int i;
+
+ for (i = 0; i < vb->nr_page_bmap; i++)
+ kfree(vb->page_bitmap[i]);
+}
+
+static void clear_page_bitmap(struct virtio_balloon *vb)
+{
+ int i;
+
+ for (i = 0; i < vb->nr_page_bmap; i++)
+ memset(vb->page_bitmap[i], 0, BALLOON_BMAP_SIZE);
+}
+
+static void send_resp_data(struct virtio_balloon *vb, struct virtqueue *vq,
+ bool busy_wait)
+{
+ struct scatterlist sg[2];
+ struct virtio_balloon_resp_hdr *hdr = vb->resp_hdr;
unsigned int len;
- sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
+ len = hdr->data_len = vb->resp_pos * sizeof(__le64);
+ sg_init_table(sg, 2);
+ sg_set_buf(&sg[0], hdr, sizeof(struct virtio_balloon_resp_hdr));
+ sg_set_buf(&sg[1], vb->resp_data, len);
+
+ if (virtqueue_add_outbuf(vq, sg, 2, vb, GFP_KERNEL) == 0) {
+ virtqueue_kick(vq);
+ if (busy_wait)
+ while (!virtqueue_get_buf(vq, &len)
+ && !virtqueue_is_broken(vq))
+ cpu_relax();
+ else
+ wait_event(vb->acked, virtqueue_get_buf(vq, &len));
+ vb->resp_pos = 0;
+ free_extended_page_bitmap(vb);
+ }
+}
- /* 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);
+static void do_set_resp_bitmap(struct virtio_balloon *vb,
+ unsigned long base_pfn, int pages)
- /* When host has read buffer, this completes via balloon_ack */
- wait_event(vb->acked, virtqueue_get_buf(vq, &len));
+{
+ __le64 *range = vb->resp_data + vb->resp_pos;
+ if (pages > (1 << VIRTIO_BALLOON_NR_PFN_BITS)) {
+ /* when the length field can't contain pages, set it to 0 to
+ * indicate the actual length is in the next __le64;
+ */
+ *range = cpu_to_le64((base_pfn <<
+ VIRTIO_BALLOON_NR_PFN_BITS) | 0);
+ *(range + 1) = cpu_to_le64(pages);
+ vb->resp_pos += 2;
+ } else {
+ *range = (base_pfn << VIRTIO_BALLOON_NR_PFN_BITS) | pages;
+ vb->resp_pos++;
+ }
+}
+
+static void set_bulk_pages(struct virtio_balloon *vb, struct virtqueue *vq,
+ unsigned long start_pfn, unsigned long *bitmap,
+ unsigned long len, bool busy_wait)
+{
+ unsigned long pos = 0, end = len * BITS_PER_BYTE;
+
+ while (pos < end) {
+ unsigned long one = find_next_bit(bitmap, end, pos);
+
+ if (one < end) {
+ unsigned long pages, zero;
+
+ zero = find_next_zero_bit(bitmap, end, one + 1);
+ if (zero >= end)
+ pages = end - one;
+ else
+ pages = zero - one;
+ if (pages) {
+ if ((vb->resp_pos + 2) * sizeof(__le64) >
+ vb->resp_buf_size)
+ send_resp_data(vb, vq, busy_wait);
+ do_set_resp_bitmap(vb, start_pfn + one, pages);
+ }
+ pos = one + pages;
+ } else
+ pos = one;
+ }
+}
+
+static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
+{
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_PAGE_RANGE)) {
+ int nr_pfn, nr_used_bmap, i;
+ unsigned long start_pfn, bmap_len;
+
+ start_pfn = vb->start_pfn;
+ nr_pfn = vb->end_pfn - start_pfn + 1;
+ nr_pfn = roundup(nr_pfn, BITS_PER_LONG);
+ nr_used_bmap = nr_pfn / PFNS_PER_BMAP;
+ if (nr_pfn % PFNS_PER_BMAP)
+ nr_used_bmap++;
+ bmap_len = nr_pfn / BITS_PER_BYTE;
+
+ for (i = 0; i < nr_used_bmap; i++) {
+ unsigned int bmap_size = BALLOON_BMAP_SIZE;
+
+ if (i + 1 == nr_used_bmap)
+ bmap_size = bmap_len - BALLOON_BMAP_SIZE * i;
+ set_bulk_pages(vb, vq, start_pfn + i * PFNS_PER_BMAP,
+ vb->page_bitmap[i], bmap_size, false);
+ }
+ if (vb->resp_pos > 0)
+ send_resp_data(vb, vq, false);
+ } else {
+ struct scatterlist sg;
+ unsigned int len;
+
+ 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);
+ virtqueue_kick(vq);
+ /* When host has read buffer, this completes via balloon_ack */
+ wait_event(vb->acked, virtqueue_get_buf(vq, &len));
+ }
}
static void set_page_pfns(struct virtio_balloon *vb,
@@ -138,13 +316,59 @@ 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 void set_page_bitmap(struct virtio_balloon *vb,
+ struct list_head *pages, struct virtqueue *vq)
+{
+ unsigned long pfn, pfn_limit;
+ struct page *page;
+ bool found;
+ int bmap_idx;
+
+ vb->min_pfn = rounddown(vb->min_pfn, BITS_PER_LONG);
+ vb->max_pfn = roundup(vb->max_pfn, BITS_PER_LONG);
+ pfn_limit = PFNS_PER_BMAP * vb->nr_page_bmap;
+
+ if (vb->nr_page_bmap == 1)
+ extend_page_bitmap(vb, vb->max_pfn - vb->min_pfn + 1);
+ for (pfn = vb->min_pfn; pfn < vb->max_pfn; pfn += pfn_limit) {
+ unsigned long end_pfn;
+
+ clear_page_bitmap(vb);
+ vb->start_pfn = pfn;
+ end_pfn = pfn;
+ found = false;
+ list_for_each_entry(page, pages, lru) {
+ unsigned long pos, balloon_pfn;
+
+ balloon_pfn = page_to_balloon_pfn(page);
+ if (balloon_pfn < pfn || balloon_pfn >= pfn + pfn_limit)
+ continue;
+ bmap_idx = (balloon_pfn - pfn) / PFNS_PER_BMAP;
+ pos = (balloon_pfn - pfn) % PFNS_PER_BMAP;
+ set_bit(pos, vb->page_bitmap[bmap_idx]);
+ if (balloon_pfn > end_pfn)
+ end_pfn = balloon_pfn;
+ found = true;
+ }
+ if (found) {
+ vb->end_pfn = end_pfn;
+ tell_host(vb, vq);
+ }
+ }
+}
+
+static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
{
struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
- unsigned num_allocated_pages;
+ unsigned int num_allocated_pages;
+ bool use_bmap = virtio_has_feature(vb->vdev,
+ VIRTIO_BALLOON_F_PAGE_RANGE);
- /* We can only do one array worth at a time. */
- num = min(num, ARRAY_SIZE(vb->pfns));
+ if (use_bmap)
+ init_bmap_pfn_range(vb);
+ else
+ /* We can only do one array worth at a time. */
+ num = min(num, ARRAY_SIZE(vb->pfns));
mutex_lock(&vb->balloon_lock);
for (vb->num_pfns = 0; vb->num_pfns < num;
@@ -159,7 +383,10 @@ 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 (use_bmap)
+ update_bmap_pfn_range(vb, page);
+ 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))
@@ -168,8 +395,13 @@ 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 (use_bmap)
+ set_page_bitmap(vb, &vb_dev_info->pages,
+ vb->inflate_vq);
+ else
+ tell_host(vb, vb->inflate_vq);
+ }
mutex_unlock(&vb->balloon_lock);
return num_allocated_pages;
@@ -189,15 +421,20 @@ 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(struct virtio_balloon *vb, size_t num)
{
- unsigned num_freed_pages;
+ unsigned int num_freed_pages;
struct page *page;
struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
LIST_HEAD(pages);
+ bool use_bmap = virtio_has_feature(vb->vdev,
+ VIRTIO_BALLOON_F_PAGE_RANGE);
- /* We can only do one array worth at a time. */
- num = min(num, ARRAY_SIZE(vb->pfns));
+ if (use_bmap)
+ init_bmap_pfn_range(vb);
+ else
+ /* We can only do one array worth at a time. */
+ num = min(num, ARRAY_SIZE(vb->pfns));
mutex_lock(&vb->balloon_lock);
/* We can't release more pages than taken */
@@ -207,7 +444,10 @@ 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 (use_bmap)
+ update_bmap_pfn_range(vb, page);
+ else
+ set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
list_add(&page->lru, &pages);
vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
}
@@ -218,8 +458,12 @@ 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 (use_bmap)
+ set_page_bitmap(vb, &pages, vb->deflate_vq);
+ else
+ tell_host(vb, vb->deflate_vq);
+ }
release_pages_balloon(vb, &pages);
mutex_unlock(&vb->balloon_lock);
return num_freed_pages;
@@ -431,6 +675,18 @@ 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)
+{
+ __le64 *range;
+
+ range = vb->resp_data + vb->resp_pos;
+ *range = cpu_to_le64((page_to_pfn(page) <<
+ VIRTIO_BALLOON_NR_PFN_BITS) | 1);
+ vb->resp_pos++;
+ send_resp_data(vb, vq, false);
+}
+
/*
* virtballoon_migratepage - perform the balloon page migration on behalf of
* a compation thread. (called under page lock)
@@ -455,6 +711,8 @@ 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);
unsigned long flags;
+ bool use_bmap = virtio_has_feature(vb->vdev,
+ VIRTIO_BALLOON_F_PAGE_RANGE);
/*
* In order to avoid lock contention while migrating pages concurrently
@@ -475,15 +733,23 @@ 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 (use_bmap)
+ 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 (use_bmap)
+ 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);
@@ -533,6 +799,29 @@ static int virtballoon_probe(struct virtio_device *vdev)
spin_lock_init(&vb->stop_update_lock);
vb->stop_update = false;
vb->num_pages = 0;
+ vb->resp_hdr = kzalloc(sizeof(struct virtio_balloon_resp_hdr),
+ GFP_KERNEL);
+ /* Clear the feature bit if memory allocation fails */
+ if (!vb->resp_hdr)
+ __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_RANGE);
+ else {
+ vb->page_bitmap[0] = kmalloc(BALLOON_BMAP_SIZE, GFP_KERNEL);
+ if (!vb->page_bitmap[0]) {
+ __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_RANGE);
+ kfree(vb->resp_hdr);
+ } else {
+ vb->nr_page_bmap = 1;
+ vb->resp_data = kmalloc(BALLOON_BMAP_SIZE, GFP_KERNEL);
+ if (!vb->resp_data) {
+ __virtio_clear_bit(vdev,
+ VIRTIO_BALLOON_F_PAGE_RANGE);
+ kfree(vb->page_bitmap[0]);
+ kfree(vb->resp_hdr);
+ }
+ }
+ }
+ vb->resp_pos = 0;
+ vb->resp_buf_size = BALLOON_BMAP_SIZE;
mutex_init(&vb->balloon_lock);
init_waitqueue_head(&vb->acked);
vb->vdev = vdev;
@@ -611,6 +900,8 @@ static void virtballoon_remove(struct virtio_device *vdev)
remove_common(vb);
if (vb->vb_dev_info.inode)
iput(vb->vb_dev_info.inode);
+ kfree_page_bitmap(vb);
+ kfree(vb->resp_hdr);
kfree(vb);
}
@@ -649,6 +940,7 @@ static int virtballoon_restore(struct virtio_device *vdev)
VIRTIO_BALLOON_F_MUST_TELL_HOST,
VIRTIO_BALLOON_F_STATS_VQ,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
+ VIRTIO_BALLOON_F_PAGE_RANGE,
};
static struct virtio_driver virtio_balloon_driver = {
--
1.9.1
Define the flags and head struct for a new host request virtual
queue. Guest can get requests from host and then responds to them on
this new virtual queue.
Host can make use of this virtual queue to request the guest do some
operations, e.g. drop page cache, synchronize file system, etc.
And the hypervisor can get some of guest's runtime information
through this virtual queue too, e.g. the guest's unused page
information, which can be used for live migration optimization.
Signed-off-by: Liang Li <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Cornelia Huck <[email protected]>
Cc: Amit Shah <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Hildenbrand <[email protected]>
---
include/uapi/linux/virtio_balloon.h | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index 2f850bf..b367020 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/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_RANGE 3 /* Send page info with ranges */
+#define VIRTIO_BALLOON_F_HOST_REQ_VQ 4 /* Host request virtqueue */
/* Size of a PFN in the balloon interface. */
#define VIRTIO_BALLOON_PFN_SHIFT 12
@@ -94,4 +95,25 @@ struct virtio_balloon_resp_hdr {
__le64 data_len: 32; /* Length of the following data, in bytes */
};
+enum virtio_balloon_req_id {
+ /* Get unused page information */
+ BALLOON_GET_UNUSED_PAGES,
+};
+
+enum virtio_balloon_flag {
+ /* Have more data for a request */
+ BALLOON_FLAG_CONT,
+ /* No more data for a request */
+ BALLOON_FLAG_DONE,
+};
+
+struct virtio_balloon_req_hdr {
+ /* Used to distinguish different requests */
+ __le16 cmd;
+ /* Reserved */
+ __le16 reserved[3];
+ /* Request parameter */
+ __le64 param;
+};
+
#endif /* _LINUX_VIRTIO_BALLOON_H */
--
1.9.1
This patch contains two parts:
One is to add a new API to mm go get the unused page information.
The virtio balloon driver will use this new API added to get the
unused page info and send it to hypervisor(QEMU) to speed up live
migration. During sending the bitmap, some the pages may be modified
and are used by the guest, this inaccuracy can be corrected by the
dirty page logging mechanism.
One is to add support the request for vm's unused page information,
QEMU can make use of unused page information and the dirty page
logging mechanism to skip the transportation of some of these unused
pages, this is very helpful to reduce the network traffic and speed
up the live migration process.
Signed-off-by: Liang Li <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Cornelia Huck <[email protected]>
Cc: Amit Shah <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Hildenbrand <[email protected]>
---
drivers/virtio/virtio_balloon.c | 144 ++++++++++++++++++++++++++++++++++++++--
include/linux/mm.h | 3 +
mm/page_alloc.c | 120 +++++++++++++++++++++++++++++++++
3 files changed, 261 insertions(+), 6 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 03383b3..b67f865 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -56,7 +56,7 @@
struct virtio_balloon {
struct virtio_device *vdev;
- struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
+ struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *req_vq;
/* The balloon servicing is delegated to a freezable workqueue. */
struct work_struct update_balloon_stats_work;
@@ -85,6 +85,8 @@ struct virtio_balloon {
unsigned int nr_page_bmap;
/* Used to record the processed pfn range */
unsigned long min_pfn, max_pfn, start_pfn, end_pfn;
+ /* Request header */
+ struct virtio_balloon_req_hdr req_hdr;
/*
* The pages we've told the Host we're not using are enqueued
* at vb_dev_info->pages list.
@@ -505,6 +507,80 @@ static void update_balloon_stats(struct virtio_balloon *vb)
pages_to_bytes(available));
}
+static void __send_unused_pages(struct virtio_balloon *vb,
+ unsigned long req_id, unsigned int pos, bool done)
+{
+ struct virtio_balloon_resp_hdr *hdr = vb->resp_hdr;
+ struct virtqueue *vq = vb->req_vq;
+
+ vb->resp_pos = pos;
+ hdr->cmd = BALLOON_GET_UNUSED_PAGES;
+ hdr->id = req_id;
+ if (!done)
+ hdr->flag = BALLOON_FLAG_CONT;
+ else
+ hdr->flag = BALLOON_FLAG_DONE;
+
+ if (pos > 0 || done)
+ send_resp_data(vb, vq, true);
+
+}
+
+static void send_unused_pages(struct virtio_balloon *vb,
+ unsigned long req_id)
+{
+ struct scatterlist sg_in;
+ unsigned int pos = 0;
+ struct virtqueue *vq = vb->req_vq;
+ int ret, order;
+ struct zone *zone = NULL;
+ bool part_fill = false;
+
+ mutex_lock(&vb->balloon_lock);
+
+ for (order = MAX_ORDER - 1; order >= 0; order--) {
+ ret = mark_unused_pages(&zone, order, vb->resp_data,
+ vb->resp_buf_size / sizeof(__le64),
+ &pos, VIRTIO_BALLOON_NR_PFN_BITS, part_fill);
+ if (ret == -ENOSPC) {
+ if (pos == 0) {
+ void *new_resp_data;
+
+ new_resp_data = kmalloc(2 * vb->resp_buf_size,
+ GFP_KERNEL);
+ if (new_resp_data) {
+ kfree(vb->resp_data);
+ vb->resp_data = new_resp_data;
+ vb->resp_buf_size *= 2;
+ } else {
+ part_fill = true;
+ dev_warn(&vb->vdev->dev,
+ "%s: part fill order: %d\n",
+ __func__, order);
+ }
+ } else {
+ __send_unused_pages(vb, req_id, pos, false);
+ pos = 0;
+ }
+
+ if (!part_fill) {
+ order++;
+ continue;
+ }
+ } else
+ zone = NULL;
+
+ if (order == 0)
+ __send_unused_pages(vb, req_id, pos, true);
+
+ }
+
+ mutex_unlock(&vb->balloon_lock);
+ sg_init_one(&sg_in, &vb->req_hdr, sizeof(vb->req_hdr));
+ virtqueue_add_inbuf(vq, &sg_in, 1, &vb->req_hdr, GFP_KERNEL);
+ virtqueue_kick(vq);
+}
+
/*
* While most virtqueues communicate guest-initiated requests to the hypervisor,
* the stats queue operates in reverse. The driver initializes the virtqueue
@@ -639,11 +715,38 @@ static void update_balloon_size_func(struct work_struct *work)
queue_work(system_freezable_wq, work);
}
+static void misc_handle_rq(struct virtio_balloon *vb)
+{
+ struct virtio_balloon_req_hdr *ptr_hdr;
+ unsigned int len;
+
+ ptr_hdr = virtqueue_get_buf(vb->req_vq, &len);
+ if (!ptr_hdr || len != sizeof(vb->req_hdr))
+ return;
+
+ switch (ptr_hdr->cmd) {
+ case BALLOON_GET_UNUSED_PAGES:
+ send_unused_pages(vb, ptr_hdr->param);
+ break;
+ default:
+ break;
+ }
+}
+
+static void misc_request(struct virtqueue *vq)
+{
+ struct virtio_balloon *vb = vq->vdev->priv;
+
+ misc_handle_rq(vb);
+}
+
static int init_vqs(struct virtio_balloon *vb)
{
- struct virtqueue *vqs[3];
- vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
- static const char * const names[] = { "inflate", "deflate", "stats" };
+ struct virtqueue *vqs[4];
+ vq_callback_t *callbacks[] = { balloon_ack, balloon_ack,
+ stats_request, misc_request };
+ static const char * const names[] = { "inflate", "deflate", "stats",
+ "misc" };
int err, nvqs;
/*
@@ -651,6 +754,18 @@ static int init_vqs(struct virtio_balloon *vb)
* optionally stat.
*/
nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HOST_REQ_VQ))
+ nvqs = 4;
+ else if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ))
+ nvqs = 3;
+ else
+ nvqs = 2;
+
+ if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
+ __virtio_clear_bit(vb->vdev, VIRTIO_BALLOON_F_PAGE_RANGE);
+ __virtio_clear_bit(vb->vdev, VIRTIO_BALLOON_F_HOST_REQ_VQ);
+ }
+
err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
if (err)
return err;
@@ -671,6 +786,18 @@ static int init_vqs(struct virtio_balloon *vb)
BUG();
virtqueue_kick(vb->stats_vq);
}
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HOST_REQ_VQ)) {
+ struct scatterlist sg_in;
+
+ vb->req_vq = vqs[3];
+ sg_init_one(&sg_in, &vb->req_hdr, sizeof(vb->req_hdr));
+ if (virtqueue_add_inbuf(vb->req_vq, &sg_in, 1,
+ &vb->req_hdr, GFP_KERNEL) < 0)
+ __virtio_clear_bit(vb->vdev,
+ VIRTIO_BALLOON_F_HOST_REQ_VQ);
+ else
+ virtqueue_kick(vb->req_vq);
+ }
return 0;
}
@@ -802,12 +929,14 @@ static int virtballoon_probe(struct virtio_device *vdev)
vb->resp_hdr = kzalloc(sizeof(struct virtio_balloon_resp_hdr),
GFP_KERNEL);
/* Clear the feature bit if memory allocation fails */
- if (!vb->resp_hdr)
+ if (!vb->resp_hdr) {
__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_RANGE);
- else {
+ __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_HOST_REQ_VQ);
+ } else {
vb->page_bitmap[0] = kmalloc(BALLOON_BMAP_SIZE, GFP_KERNEL);
if (!vb->page_bitmap[0]) {
__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_RANGE);
+ __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_HOST_REQ_VQ);
kfree(vb->resp_hdr);
} else {
vb->nr_page_bmap = 1;
@@ -815,6 +944,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
if (!vb->resp_data) {
__virtio_clear_bit(vdev,
VIRTIO_BALLOON_F_PAGE_RANGE);
+ __virtio_clear_bit(vdev,
+ VIRTIO_BALLOON_F_HOST_REQ_VQ);
kfree(vb->page_bitmap[0]);
kfree(vb->resp_hdr);
}
@@ -941,6 +1072,7 @@ static int virtballoon_restore(struct virtio_device *vdev)
VIRTIO_BALLOON_F_STATS_VQ,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
VIRTIO_BALLOON_F_PAGE_RANGE,
+ VIRTIO_BALLOON_F_HOST_REQ_VQ,
};
static struct virtio_driver virtio_balloon_driver = {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4424784..a80b8f3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1762,6 +1762,9 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd)
extern void free_area_init_node(int nid, unsigned long * zones_size,
unsigned long zone_start_pfn, unsigned long *zholes_size);
extern void free_initmem(void);
+extern int mark_unused_pages(struct zone **start_zone, int order,
+ __le64 *pages, unsigned int size, unsigned int *pos,
+ u8 len_bits, bool part_fill);
/*
* Free reserved pages within range [PAGE_ALIGN(start), end & PAGE_MASK)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2c6d5f6..de0e7a4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4479,6 +4479,126 @@ void show_free_areas(unsigned int filter)
show_swap_cache_info();
}
+static int __mark_unused_pages(struct zone *zone, int order,
+ __le64 *pages, unsigned int size, unsigned int *pos,
+ u8 len_bits, bool part_fill)
+{
+ unsigned long pfn, flags;
+ int t, ret = 0;
+ struct list_head *curr;
+ __le64 *range;
+
+ if (zone_is_empty(zone))
+ return 0;
+
+ spin_lock_irqsave(&zone->lock, flags);
+
+ if (*pos + zone->free_area[order].nr_free > size && !part_fill) {
+ ret = -ENOSPC;
+ goto out;
+ }
+ for (t = 0; t < MIGRATE_TYPES; t++) {
+ list_for_each(curr, &zone->free_area[order].free_list[t]) {
+ pfn = page_to_pfn(list_entry(curr, struct page, lru));
+ range = pages + *pos;
+ if (order < len_bits) {
+ if (*pos + 1 > size) {
+ ret = -ENOSPC;
+ goto out;
+ }
+ *range = cpu_to_le64((pfn << len_bits)
+ | 1 << order);
+ *pos += 1;
+ } else {
+ if (*pos + 2 > size) {
+ ret = -ENOSPC;
+ goto out;
+ }
+ *range = cpu_to_le64((pfn << len_bits) | 0);
+ *(range + 1) = cpu_to_le64(1 << order);
+ *pos += 2;
+ }
+ }
+ }
+
+out:
+ spin_unlock_irqrestore(&zone->lock, flags);
+
+ return ret;
+}
+
+/*
+ * During live migration, page is discardable unless it's content
+ * is needed by the system.
+ * mark_unused_pages provides an API to mark the unused pages, these
+ * unused pages can be discarded if there is no modification since
+ * the request. Some other mechanism, like the dirty page logging
+ * can be used to track the modification.
+ *
+ * This function scans the free page list to mark the unused pages
+ * with the specified order, and set the corresponding range element
+ * in the array 'pages' if unused pages are found for the specified
+ * order.
+ *
+ * @start_zone: zone to start the mark operation.
+ * @order: page order to mark.
+ * @pages: array to save the unused page info.
+ * @size: size of array pages.
+ * @pos: offset in the array to save the page info.
+ * @len_bits: bits for the length field of the range.
+ * @part_fill: indicate if partial fill is used.
+ *
+ * return -EINVAL if parameter is invalid
+ * return -ENOSPC when bitmap can't contain the pages
+ * return 0 when sccess
+ */
+int mark_unused_pages(struct zone **start_zone, int order,
+ __le64 *pages, unsigned int size, unsigned int *pos,
+ u8 len_bits, bool part_fill)
+{
+ struct zone *zone;
+ int ret = 0;
+ bool skip_check = false;
+
+ /* make sure all the parameters are valid */
+ if (pages == NULL || pos == NULL || *pos < 0
+ || order >= MAX_ORDER || len_bits > 64)
+ return -EINVAL;
+ if (*start_zone != NULL) {
+ bool found = false;
+
+ for_each_populated_zone(zone) {
+ if (zone != *start_zone)
+ continue;
+ found = true;
+ break;
+ }
+ if (!found)
+ return -EINVAL;
+ } else
+ skip_check = true;
+
+ for_each_populated_zone(zone) {
+ /* Start from *start_zone if it's not NULL */
+ if (!skip_check) {
+ if (*start_zone != zone)
+ continue;
+ else
+ skip_check = true;
+ }
+ ret = __mark_unused_pages(zone, order, pages, size,
+ pos, len_bits, part_fill);
+ if (ret < 0) {
+ /* record the failed zone */
+ *start_zone = zone;
+ break;
+ }
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL(mark_unused_pages);
+
static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
{
zoneref->zone = zone;
--
1.9.1
Add a new feature which supports sending the page information
with range array. The current implementation uses PFNs array,
which is not very efficient. Using ranges can improve the
performance of inflating/deflating significantly.
Signed-off-by: Liang Li <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Cornelia Huck <[email protected]>
Cc: Amit Shah <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Hildenbrand <[email protected]>
---
include/uapi/linux/virtio_balloon.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index 343d7dd..2f850bf 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -34,10 +34,14 @@
#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_RANGE 3 /* Send page info with ranges */
/* Size of a PFN in the balloon interface. */
#define VIRTIO_BALLOON_PFN_SHIFT 12
+/* Bits width for the length of the pfn range */
+#define VIRTIO_BALLOON_NR_PFN_BITS 12
+
struct virtio_balloon_config {
/* Number of pages host wants Guest to give up. */
__u32 num_pages;
@@ -82,4 +86,12 @@ struct virtio_balloon_stat {
__virtio64 val;
} __attribute__((packed));
+/* Response header structure */
+struct virtio_balloon_resp_hdr {
+ __le64 cmd : 8; /* Distinguish different requests type */
+ __le64 flag: 8; /* Mark status for a specific request type */
+ __le64 id : 16; /* Distinguish requests of a specific type */
+ __le64 data_len: 32; /* Length of the following data, in bytes */
+};
+
#endif /* _LINUX_VIRTIO_BALLOON_H */
--
1.9.1