[PATCH 2/5] vsock/virtio: Resize receive buffers so that each SKB fits in a page
From: Will Deacon <will@kernel.org>
Date: 2025-06-25 13:15:56
Also in:
lkml, virtualization
Subsystem:
the rest, virtio and vhost vsock driver, virtio core · Maintainers:
Linus Torvalds, Stefan Hajnoczi, Stefano Garzarella, "Michael S. Tsirkin", Jason Wang
When allocating receive buffers for the vsock virtio RX virtqueue, an SKB is allocated with a 4140 data payload (the 44-byte packet header + VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE). Even when factoring in the SKB overhead, the resulting 8KiB allocation thanks to the rounding in kmalloc_reserve() is wasteful (~3700 unusable bytes) and results in a higher-order page allocation for the sake of a few hundred bytes of packet data. Limit the vsock virtio RX buffers to a page per SKB, resulting in much better memory utilisation and removing the need to allocate higher-order pages entirely. Signed-off-by: Will Deacon <will@kernel.org> --- include/linux/virtio_vsock.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 36fb3edfa403..67ffb64325ef 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h@@ -111,7 +111,8 @@ static inline size_t virtio_vsock_skb_len(struct sk_buff *skb) return (size_t)(skb_end_pointer(skb) - skb->head); } -#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (1024 * 4) +#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (SKB_WITH_OVERHEAD(PAGE_SIZE) \ + - VIRTIO_VSOCK_SKB_HEADROOM) #define VIRTIO_VSOCK_MAX_BUF_SIZE 0xFFFFFFFFUL #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE (1024 * 64)
--
2.50.0.714.g196bf9f422-goog