On Fri, Jun 27, 2025 at 12:50:27PM +0200, Stefano Garzarella wrote: > nit: I'd use `vsock/virtio: ` prefix since we are touching the virtio > transport common code. Maybe we can mention that this will affect both > virtio and vhost transports. Sure, I'll do that. > On Wed, Jun 25, 2025 at 02:15:43PM +0100, Will Deacon wrote: > > 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@xxxxxxxxxx> > > --- > > 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); > > + > > As I mentioned in the other patch, we may avoid this code duplication hiding > this in virtio_vsock_alloc_skb() or adding a new function that > we can use when we want to allocate frags or not. That would be good. I had a crack at it in the diff I sent in reply to the earlier patch, so please take a look. Will
