netdev - Re: [PATCH] tun: use netif_receive_skb instead of netif_rx

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Message-ID: <52FB2574.4070004@redhat.com>
Date:	Wed, 12 Feb 2014 15:40:36 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Qin Chuanyu <qinchuanyu@...wei.com>, davem@...emloft.net
CC:	"Michael S. Tsirkin" <mst@...hat.com>,
	Anthony Liguori <anthony@...emonkey.ws>,
	KVM list <kvm@...r.kernel.org>, netdev@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH] tun: use netif_receive_skb instead of netif_rx_ni

On 02/12/2014 02:46 PM, Qin Chuanyu wrote:
> On 2014/2/12 13:28, Jason Wang wrote:
>
>> A question: without NAPI weight, could this starve other net devices?
> tap xmit skb use thread context，the poll func of physical nic driver
> could be called in softirq context without change.
>
> I had test it by binding vhost thread and physic nic interrupt on the
> same vcpu, use netperf xmit udp, test model is VM1-Host1-Host2.
>
> if only VM1 xmit skb, the top show as below :
> Cpu1 :0.0%us, 95.0%sy, 0.0%ni, 0.0%id,  0.0%wa, 0.0%hi, 5.0%si,  0.0%st
>
> then use host2 xmit skb to VM1, the top show as below :
> Cpu1 :0.0%us, 41.0%sy, 0.0%ni, 0.0%id,  0.0%wa, 0.0%hi, 59.0%si, 0.0%st
>
> so I think there is no problem with this change.

Yes, I realize it was ok after Eric's comment.

Thanks
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