When host_zeroes_pages is set, the host has zeroed the balloon pages on reclaim. Use put_page_zeroed() during deflation so the freed pages are marked as zeroed in the buddy allocator, allowing the next allocation to skip redundant zeroing.
put_page_zeroed() is best-effort: if the balloon is the sole holder (the common case), the zeroed hint reaches the buddy allocator via free_frozen_pages_zeroed(). If someone else holds a reference, the hint is silently lost. Once balloon pages are converted to frozen pages (no refcount), this can switch to free_frozen_pages_zeroed() directly. Signed-off-by: Michael S. Tsirkin <[email protected]> Assisted-by: Claude:claude-opus-4-6 --- drivers/virtio/virtio_balloon.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 8c15530b51b3..cdc3c960397d 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -304,7 +304,10 @@ static void release_pages_balloon(struct virtio_balloon *vb, list_for_each_entry_safe(page, next, pages, lru) { list_del(&page->lru); - put_page(page); /* balloon reference */ + if (host_zeroes_pages && !page_poisoning_enabled_static()) + put_page_zeroed(page); + else + put_page(page); /* balloon reference */ } } -- MST
