From: Jason Wang <jasowang@xxxxxxxxxx>
Date: Fri, 30 Dec 2016 13:20:51 +0800
> @@ -1283,10 +1314,15 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> skb_probe_transport_header(skb, 0);
>
> rxhash = skb_get_hash(skb);
> +
> #ifndef CONFIG_4KSTACKS
> - local_bh_disable();
> - netif_receive_skb(skb);
> - local_bh_enable();
> + if (!rx_batched) {
> + local_bh_disable();
> + netif_receive_skb(skb);
> + local_bh_enable();
> + } else {
> + tun_rx_batched(tfile, skb, more);
> + }
> #else
> netif_rx_ni(skb);
> #endif
If rx_batched has been set, and we are talking to clients not using
this new MSG_MORE facility (or such clients don't have multiple TX
packets to send to you, thus MSG_MORE is often clear), you are doing a
lot more work per-packet than the existing code.
You take the queue lock, you test state, you splice into a local queue
on the stack, then you walk that local stack queue to submit just one
SKB to netif_receive_skb().
I think you want to streamline this sequence in such cases so that the
cost before and after is similar if not equivalent.
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