netdev - Re: [PATCH v3] net: batch skb dequeueing from softnet input_pkt

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Date:	Wed, 14 Apr 2010 20:13:20 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	hadi@...erus.ca
Cc:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v3] net: batch skb dequeueing from softnet input_pkt_queue

On Wed, Apr 14, 2010 at 7:58 PM, jamal <hadi@...erus.ca> wrote:
>
> It seems we are now going to generate a lot more IPIs with such a
> change. At least this is what i am imagining.
> CPU0: packet comes in,queue empty, generate an IPI to CPU1
> CPU0: second packet comes in, enqueue
> CPU1: grab two packets to process and run with them
> CPU0: packet comes in,queue empty, generate an IPI to CPU1

No extra IPI is needed.

+       qlen = queue->input_pkt_queue.qlen + queue->processing_queue.qlen;
+       if (qlen <= netdev_max_backlog) {
+               if (qlen) {

the packets in processing_queue are counted too.

>
> IPIs add to latency (refer to my other email). Did you test this
> to reach some conclusion that it improves thing or was it just by
> inspection?
>

:( only insepection.

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