[PATCH 5/5] vhost/vsock: Allocate nonlinear SKBs for handling large transmit buffers
From: Will Deacon <will@kernel.org>
Date: 2025-06-25 13:16:04
Also in:
lkml, virtualization
Subsystem:
networking [general], the rest, virtio and vhost vsock driver, virtio core, vm sockets (af_vsock) · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Stefan Hajnoczi, Stefano Garzarella, "Michael S. Tsirkin", Jason Wang
When transmitting a vsock packet, virtio_transport_send_pkt_info() calls virtio_transport_alloc_skb() to allocate and fill SKBs with the transmit data. Unfortunately, these are always linear allocations and can therefore result in significant pressure on kmalloc() considering that the maximum packet size (VIRTIO_VSOCK_MAX_PKT_BUF_SIZE + VIRTIO_VSOCK_SKB_HEADROOM) is a little over 64KiB, resulting in a 128KiB allocation for each packet. Rework the vsock SKB allocation so that, for sizes with page order greater than PAGE_ALLOC_COSTLY_ORDER, a nonlinear SKB is allocated instead with the packet header in the SKB and the transmit data in the fragments. Signed-off-by: Will Deacon <will@kernel.org> --- net/vmw_vsock/virtio_transport_common.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 1b5d9896edae..424eb69e84f9 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c@@ -109,7 +109,8 @@ static int virtio_transport_fill_skb(struct sk_buff *skb, return __zerocopy_sg_from_iter(info->msg, NULL, skb, &info->msg->msg_iter, len, NULL); - return memcpy_from_msg(skb_put(skb, len), info->msg, len); + virtio_vsock_skb_put(skb); + return skb_copy_datagram_from_iter(skb, 0, &info->msg->msg_iter, len); } static void virtio_transport_init_hdr(struct sk_buff *skb,
@@ -261,7 +262,11 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info * if (!zcopy) skb_len += payload_len; - skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL); + if (skb_len > SKB_WITH_OVERHEAD(PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) + skb = virtio_vsock_alloc_skb_with_frags(skb_len, GFP_KERNEL); + else + skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL); + if (!skb) return NULL;
--
2.50.0.714.g196bf9f422-goog