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

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Message-ID: <1392186384.1752.9.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 11 Feb 2014 22:26:24 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	Qin Chuanyu <qinchuanyu@...wei.com>, davem@...emloft.net,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Anthony Liguori <anthony@...emonkey.ws>,
	KVM list <kvm@...r.kernel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH] tun: use netif_receive_skb instead of netif_rx_ni

On Wed, 2014-02-12 at 13:50 +0800, Jason Wang wrote:
> On 02/12/2014 01:47 PM, Eric Dumazet wrote:
> > On Wed, 2014-02-12 at 13:28 +0800, Jason Wang wrote:
> >
> >> A question: without NAPI weight, could this starve other net devices?
> > Not really, as net devices are serviced by softirq handler.
> >
> >
> 
> Yes, then the issue is tun could be starved by other net devices.

How this patch changes anything to this 'problem' ?

netif_rx_ni() can only be called if your process is not preempted by
other high prio tasks/softirqs.

If this process is scheduled on a cpu, then disabling bh to process
_one_ packet wont fundamentally change dynamic of the system.



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