Re: tcp wifi upload performance and lots of ACKs
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From: Daniel Baluta <hidden>
Date: 2012-06-04 20:15:48
On Mon, Jun 4, 2012 at 11:09 PM, Ben Greear [off-list ref] wrote:
On 06/04/2012 12:22 PM, Daniel Baluta wrote:quoted
On Mon, Jun 4, 2012 at 9:29 PM, Ben Greear[off-list ref] wrote:quoted
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.