netdev - Re: tcp wifi upload performance and lots of ACKs

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Date:	Mon, 4 Jun 2012 23:15:48 +0300
From:	Daniel Baluta <dbaluta@...acom.com>
To:	Ben Greear <greearb@...delatech.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: tcp wifi upload performance and lots of ACKs

On Mon, Jun 4, 2012 at 11:09 PM, Ben Greear <greearb@...delatech.com> wrote:
> On 06/04/2012 12:22 PM, Daniel Baluta wrote:
>>
>> On Mon, Jun 4, 2012 at 9:29 PM, Ben Greear<greearb@...delatech.com>
>>  wrote:
>>>
>>> I'm going some TCP performance testing on wifi ->  LAN interface
>>> connections.
>>>  With
>>> UDP, we can get around 250Mbps of payload throughput.  With TCP, max is
>>> about 80Mbps.
>>>
>>> I think the problem is that there are way too many ACK packets, and
>>> bi-directional
>>> traffic on wifi interfaces really slows things down.  (About 7000 pkts
>>> per
>>> second in
>>> upload direction, 2000 pps download.  And the vast majority of the
>>> download
>>> pkts
>>> are 66 byte ACK pkts from what I can tell.)
>>>
>>> Kernel is 3.3.7+
>>>
>>> Anyone know of any tuning parameters that would let the receiving socket
>>> wait a
>>> bit longer and send more ACK data in fewer packets?
>>
>>
>> An ACK is generated after every second full sized segment or a timeout
>> expires.
>>
>> Currently, there is no way to tune these parameters. Here is an
>> experimental
>> patch [1]. If anyone, thinks that this patch has a chance to get accepted
>> I will be happily try to further improve it.
>
>
> It looks like it could be useful for my case, but I would also want
> per-socket options to set the min/max ack delay so that the settings
> are not just system-wide.
>
> I can at least test this, and perhaps even hack on the code if
> you are not interested in the per-socket settings...

Yes, indeed this should be a per socket option. I will be
back with a patch in the next days.

Meanwhile, it would be great if you could test my previous patch.

thanks,
Daniel.
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