Re: tcp wifi upload performance and lots of ACKs
On 06/04/2012 12:32 PM, Eric Dumazet wrote:
On Mon, 2012-06-04 at 11:29 -0700, Ben Greear 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?Well, thats half duplex days...
WiFi is still half-duplex, and isn't changing any time soon I think.
There is the ACK every 2 packets rule of thumb, so that tcp sender can increase its cwnd. Then, some folks tried submitting patches to make '2' more like 10 or 15, but this went nowhere. Other idea is to arm a timer and defer ACK sending, in the hope we receive another packet very soon.
From a quick read of Daniel's patch..it seems there is already a timer that could be used for this?
That could be done with a special qdisc, sort of netem...
That sounds like a horrible hack :) Ben -- Ben Greear <greearb@xxxxxxxxxxxxxxx> Candela Technologies Inc http://www.candelatech.com -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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