Re: tcp wifi upload performance and lots of ACKs

[Ben Greear <greearb@xxxxxxxxxxxxxxx>]

On 06/04/2012 12:22 PM, Daniel Baluta wrote:
> On Mon, Jun 4, 2012 at 9:29 PM, Ben Greear<greearb@xxxxxxxxxxxxxxx>  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...

Thanks,
Ben

--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com

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