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vsock/virtio: limit the memory used per-socket

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Since virtio-vsock was introduced, the buffers filled by the host
and pushed to the guest using the vring, are directly queued in
a per-socket list. These buffers are preallocated by the guest
with a fixed size (4 KB).

The maximum amount of memory used by each socket should be
controlled by the credit mechanism.
The default credit available per-socket is 256 KB, but if we use
only 1 byte per packet, the guest can queue up to 262144 of 4 KB
buffers, using up to 1 GB of memory per-socket. In addition, the
guest will continue to fill the vring with new 4 KB free buffers
to avoid starvation of other sockets.

This patch mitigates this issue copying the payload of small
packets (< 128 bytes) into the buffer of last packet queued, in
order to avoid wasting memory.

Signed-off-by: Stefano Garzarella <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Stefano Garzarella 2019-07-30 17:43:30 +02:00 • committed by David S. Miller
commit 473c7391ce
4 changed files with 55 additions and 9 deletions
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2
drivers/vhost/vsock.c
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@ -329,6 +329,8 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
return NULL;
}
pkt->buf_len = pkt->len;
nbytes = copy_from_iter(pkt->buf, pkt->len, &iov_iter);
if (nbytes != pkt->len) {
vq_err(vq, "Expected %u byte payload, got %zu bytes\n",