@@ -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;
}
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 <liang.z.li@intel.com> Signed-off-by: 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> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Hildenbrand <david@redhat.com> --- drivers/virtio/virtio_balloon.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-)