Re: [PATCH net-next 1/2] vsock/virtio: refactor virtio_transport_send_pkt_work

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On Fri, Jun 14, 2024 at 03:55:42PM GMT, Luigi Leonardi wrote:
From: Marco Pinna <marco.pinn95@xxxxxxxxx>

This is a preliminary patch to introduce an optimization to
the enqueue system.

All the code used to enqueue a packet into the virtqueue
is removed from virtio_transport_send_pkt_work()
and moved to the new virtio_transport_send_skb() function.

Co-developed-by: Luigi Leonardi <luigi.leonardi@xxxxxxxxxxx>
Signed-off-by: Luigi Leonardi <luigi.leonardi@xxxxxxxxxxx>
Signed-off-by: Marco Pinna <marco.pinn95@xxxxxxxxx>
---
net/vmw_vsock/virtio_transport.c | 134 +++++++++++++++++--------------
1 file changed, 74 insertions(+), 60 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 43d405298857..c930235ecaec 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -94,6 +94,78 @@ static u32 virtio_transport_get_local_cid(void)
	return ret;
}

+/* Caller need to hold vsock->tx_lock on vq */
+static int virtio_transport_send_skb(struct sk_buff *skb, struct virtqueue *vq,
+				     struct virtio_vsock *vsock, bool *restart_rx)
+{
+	int ret, in_sg = 0, out_sg = 0;
+	struct scatterlist **sgs;
+	bool reply;
+
+	reply = virtio_vsock_skb_reply(skb);
+	sgs = vsock->out_sgs;
+	sg_init_one(sgs[out_sg], virtio_vsock_hdr(skb),
+		    sizeof(*virtio_vsock_hdr(skb)));
+	out_sg++;
+
+	if (!skb_is_nonlinear(skb)) {
+		if (skb->len > 0) {
+			sg_init_one(sgs[out_sg], skb->data, skb->len);
+			out_sg++;
+		}
+	} else {
+		struct skb_shared_info *si;
+		int i;
+
+		/* If skb is nonlinear, then its buffer must contain
+		 * only header and nothing more. Data is stored in
+		 * the fragged part.
+		 */
+		WARN_ON_ONCE(skb_headroom(skb) != sizeof(*virtio_vsock_hdr(skb)));
+
+		si = skb_shinfo(skb);
+
+		for (i = 0; i < si->nr_frags; i++) {
+			skb_frag_t *skb_frag = &si->frags[i];
+			void *va;
+
+			/* We will use 'page_to_virt()' for the userspace page
+			 * here, because virtio or dma-mapping layers will call
+			 * 'virt_to_phys()' later to fill the buffer descriptor.
+ * We don't touch memory at "virtual" address of this page.
+			 */
+			va = page_to_virt(skb_frag_page(skb_frag));
+			sg_init_one(sgs[out_sg],
+				    va + skb_frag_off(skb_frag),
+				    skb_frag_size(skb_frag));
+			out_sg++;
+		}
+	}
+
+	ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
+	/* Usually this means that there is no more space available in
+	 * the vq
+	 */
+	if (ret < 0)
+		goto out;

We use the `out` label just here, so what about remove it since we just return ret?

I mean:

	if (ret < 0)
		return ret;

...

+
+	virtio_transport_deliver_tap_pkt(skb);
+
+	if (reply) {
+		struct virtqueue *rx_vq = vsock->vqs[VSOCK_VQ_RX];
+		int val;
+
+		val = atomic_dec_return(&vsock->queued_replies);
+
+		/* Do we now have resources to resume rx processing? */
+		if (val + 1 == virtqueue_get_vring_size(rx_vq))
+			*restart_rx = true;
+	}
+

	return 0;
}

+out:
+	return ret;
+}
+
static void
virtio_transport_send_pkt_work(struct work_struct *work)
{
@@ -111,77 +183,19 @@ virtio_transport_send_pkt_work(struct work_struct *work)
	vq = vsock->vqs[VSOCK_VQ_TX];

	for (;;) {
-		int ret, in_sg = 0, out_sg = 0;
-		struct scatterlist **sgs;
		struct sk_buff *skb;
-		bool reply;
+		int ret;

		skb = virtio_vsock_skb_dequeue(&vsock->send_pkt_queue);
		if (!skb)
			break;

-		reply = virtio_vsock_skb_reply(skb);
-		sgs = vsock->out_sgs;
-		sg_init_one(sgs[out_sg], virtio_vsock_hdr(skb),
-			    sizeof(*virtio_vsock_hdr(skb)));
-		out_sg++;
-
-		if (!skb_is_nonlinear(skb)) {
-			if (skb->len > 0) {
-				sg_init_one(sgs[out_sg], skb->data, skb->len);
-				out_sg++;
-			}
-		} else {
-			struct skb_shared_info *si;
-			int i;
+		ret = virtio_transport_send_skb(skb, vq, vsock, &restart_rx);


nit: I'd remove this new line here.

-			/* If skb is nonlinear, then its buffer must contain
-			 * only header and nothing more. Data is stored in
-			 * the fragged part.
-			 */
-			WARN_ON_ONCE(skb_headroom(skb) != sizeof(*virtio_vsock_hdr(skb)));
-
-			si = skb_shinfo(skb);
-
-			for (i = 0; i < si->nr_frags; i++) {
-				skb_frag_t *skb_frag = &si->frags[i];
-				void *va;
-
-				/* We will use 'page_to_virt()' for the userspace page
-				 * here, because virtio or dma-mapping layers will call
-				 * 'virt_to_phys()' later to fill the buffer descriptor.
-				 * We don't touch memory at "virtual" address of this page.
-				 */
-				va = page_to_virt(skb_frag_page(skb_frag));
-				sg_init_one(sgs[out_sg],
-					    va + skb_frag_off(skb_frag),
-					    skb_frag_size(skb_frag));
-				out_sg++;
-			}
-		}
-
- ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL); - /* Usually this means that there is no more space available in
-		 * the vq
-		 */
		if (ret < 0) {
			virtio_vsock_skb_queue_head(&vsock->send_pkt_queue, skb);
			break;
		}
-
-		virtio_transport_deliver_tap_pkt(skb);
-
-		if (reply) {
-			struct virtqueue *rx_vq = vsock->vqs[VSOCK_VQ_RX];
-			int val;
-
-			val = atomic_dec_return(&vsock->queued_replies);
-
-			/* Do we now have resources to resume rx processing? */
-			if (val + 1 == virtqueue_get_vring_size(rx_vq))
-				restart_rx = true;
-		}
-

nit: maybe I'd move the empty line here.


Our usual style is:
        ret = foo();
        if (ret < 0) {
            //error handling
        }

        next_stuff...

Thanks,
Stefano

		added = true;
	}

--
2.45.2






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