[Make-wifi-fast] emulating wifi better - coupling qdiscs in netem?

Eric Dumazet eric.dumazet at gmail.com
Mon Jun 18 12:08:20 EDT 2018

On 06/18/2018 02:24 AM, Pete Heist wrote:
>> On Jun 17, 2018, at 8:47 PM, Jonathan Morton <chromatix99 at gmail.com <mailto:chromatix99 at gmail.com>> wrote:
>> If you have instructions for setting up a test, I could try it.
> Ok, thanks for that, code and scripts are attached, see README.txt.
> I now use plain netns (no lxc containers), which is easier to set up and has lower RTTs and higher throughputs, probably due to no bridge device.
> Per Eric’s tip, the nfq no-op code is run with chrt -rr 99, which reduces RTTs somewhat and increases throughputs ~2-3x. No busy polling yet.
> I also tried it on VMWare with a 2011 MBP, which looks radically better than the APU2 (for nfq, RTTs ~16% of APU2 and throughput 4x higher in the non-GSO case, 11x with GSO). Results attached, and to summarize:
> ping mean (min-max) RTTs:
> APU2, no nfq: 35 us (23-291)
> APU2, nfq without GSO: 80 us (53-288)
> APU2, nfq with GSO: 85 us (56-270)
> 2011 MBP, no nfq: 4 us (4-529) [11% of APU2]
> 2011 MBP, nfq without GSO: 13 us (11-197) [16% of APU2]
> 2011 MBP, nfq with GSO: 14 us (11-1568) [16% of APU2]
> iperf3 throughputs (Gbps):
> APU2, no nfq: 5.01 Gbps
> APU2, nfq without GSO: 391 Mbps
> APU2, nfq with GSO: 3.35 Gbps
> 2011 MBP, no nfq: 39.8 Gbps [7.9x APU2]
> 2011 MBP, nfq without GSO: 1.48 Gbps [3.8x APU2]
> 2011 MBP, nfq with GSO: 38.0 Gbps [11.3x APU2]
> Results from a decent physical box instead of a VM may be interesting to see.

If all you want to achieve is to delay packets given a set of rules, you do not want the content of them.

Copying the packets to user space is not needed, you are not doing deep packet inspection.

Really the throughput should be the same, only latencies should be somehow increased,

nfq_set_mode(qh, NFQNL_COPY_PACKET, 0xffff)


nfq_set_mode(qh, NFQNL_COPY_PACKET, 128); // assuming you want to inspect headers

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