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Re: [Qemu-devel] Slow inbound traffic on macvtap interfaces
From: |
Richard Davies |
Subject: |
Re: [Qemu-devel] Slow inbound traffic on macvtap interfaces |
Date: |
Thu, 30 Aug 2012 09:20:57 +0100 |
User-agent: |
Mutt/1.5.20 (2009-06-14) |
Chris Webb wrote:
> I found that on my laptop, the single change of host kernel config
>
> -CONFIG_INTEL_IDLE=y
> +# CONFIG_INTEL_IDLE is not set
>
> is sufficient to turn transfers into guests from slow to full wire speed
I am not deep enough in this code to write a patch, but I wonder if
macvtap_forward in macvtap.c is missing a call to kill_fasync, which I
understand is used to signal to interested processes when data arrives?
Here is the end of macvtap_forward:
skb_queue_tail(&q->sk.sk_receive_queue, skb);
wake_up_interruptible_poll(sk_sleep(&q->sk), POLLIN | POLLRDNORM |
POLLRDBAND);
return NET_RX_SUCCESS;
Compared to this end of tun_net_xmit in tun.c:
/* Enqueue packet */
skb_queue_tail(&tun->socket.sk->sk_receive_queue, skb);
/* Notify and wake up reader process */
if (tun->flags & TUN_FASYNC)
kill_fasync(&tun->fasync, SIGIO, POLL_IN);
wake_up_interruptible_poll(&tun->wq.wait, POLLIN |
POLLRDNORM | POLLRDBAND);
return NETDEV_TX_OK;
Richard.