netdev - Re: [PATCH v2] net: batch skb dequeueing from softnet input_pkt

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Date:	Tue, 13 Apr 2010 21:38:32 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v2] net: batch skb dequeueing from softnet input_pkt_queue

On Tue, Apr 13, 2010 at 9:21 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> This is a problem of cooperation between flush_backlog() and
> process_backlog(). Dont allow flush_backlog() to return if
> process_backlog() is running. Exactly as before, but lock acquisition
> done in flush_backlog() should be a bit smarter.
>

flush_backlog() is called in IRQ context. Unless you disable irq in
process_backlog(), you can't block flush_backlog().

>
>> Oh, my GOD. When RPS is enabled, if flush_backlog(eth0) is called on
>> CPU1 when a skb0(eth0) is dequeued from CPU0's softnet and isn't
>> queued to CPU1's softnet, what will happen?
>>
>
> I am a bit lost here. flush_backlog() drops skbs, not requeue them.
>

I mean flush_backlog() don't drop all the packets, whose dev point to
a special net_device and can't be processed before the net_device
disappers.

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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