netdev - Re: Softirqs without captured packets

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Date:	Sun, 10 Feb 2013 04:02:47 +0100
From:	Javier Domingo <javierdo1@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: Softirqs without captured packets

Well, that explains why the 0 :D. I was getting nut. Any way, does
that happen in e1000e or tg3 drivers? If not, then there is still
without explanation.

Respecting the low numbers, I will do some futher stress tests, but
this measures where done pinging the computer at 0.001 interval:

ping -i 0.0001 <computer ip>

And received packets where at much, 3 per softirq. Also, I tried
opening an ftp download session but didn't get much high numbers
(1Gbps link).

When I tried this with the injection done by a dag (hardware injector)
there were strange results because thought the 0s where explained, the
were appearing thought the rest of softirqs where about 280+-50.

I have done some testing remotelly with a dag, and I will post here
the results after monday when I return to the lab.

I will check meanwhile for the drivers that we use in the lab that
have that tx completion in their polling call.

Thank you,

Javier Domingo

2013/2/10 Eric Dumazet <eric.dumazet@...il.com>:
> On Sat, 2013-02-09 at 21:27 +0100, Javier Domingo wrote:
>> Can you tell me something about the traces I introduced?
>>
>> I tried to insert the trace the cleanest way possible. I patched
>> dev.c, in the measurement places and tried to make the module the more
>> independent I could. It makes the measure with sched_clock() and in
>> each round, it sums up the work done.
>>
>> I have supposed that that softirq is just for capturing packets, so
>> that is why I asked my first question,
>
> Seems pretty easy to understand to me.
>
> A network device receives and transmits packets.
>
> n->poll() call done in net_rx_action() can both :
>
> - Receive packets
> - Perform the TX completion for most devices (some of them still
>   use a hard IRQ driven TX completion path)
>
> The return value is only about receive part.
>
> (The TX completion is not limited by a per round quota)
>
>
>
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