Zyxel nbg6617/ipq4019 regression in Wifi 5GHz

I got the default packages, so CONFIG_DEFAULT_wpad-basic=y
But I started using the the rc2 official build first with the same issue.

I tried both the ath10k and ath10k-ct with all the firmwares available(ct and official). Nothing strange in the syslog except a lot of disconnect from the laptop with the Broadcom 802.11an card repeatedly trying to connect.

The only warning? I've seen in kernel log related to the 5G network was this:
ath10k_ahb a800000.wifi: Invalid VHT mcs 15 peer stats
but I'm not sure it's an error or a warning.

I have this too. It doesn't affect anything.

I don't have any Broadcom or marvel clients.

Try to connect only one device at a time.

Just to add to the information here - I experienced similar issues with an Archer C7 V2 on 5 GHz with a MS Surface client (Marvel Avastar 802.11ac device). See my bug report at FS#2563. I was seeing high (but useable) latency prior to the change I bisected to on 11 Sep 2019, after that date the latency went to seconds and stopped the MS surface doing anything sensible.

The hostapd 2.9 update happened on 10 Aug 2019. I suspect that this indeed was the cause of the issue but was unable to revert the change in later snapshots.

I'm also using the surface client, so that seems like a common issue. I made bug a report at FS#2679 and at least one more person has the exact same issue on the Archer C7 v2 @systemcrash If you are willing to try I made for him a build of 19.07 with hostapd 2.8. He had some problems with the openwrt configuration but my build seemed to boot and work somewhat. If it's not your primary router maybe you can give it a try.

Maybe @systemcrash sees the ping in this message and can chime in with some update.

Message received. Will give your build another try (just requires re-working the radio config). Going to give 19.07.0 a try first - see if there are any improvements there.

Edit: 19.07.0 - still shit on 5GHz.

Edit 2: @hgblob 19.07.0-rc2 custom build - check your inbox - could not get 5GHz online.

1 Like

I use the Archer C7 as one of two AP-only devices in the house. It will be no problem to try your build.

I have a pair of EA6350 v3. I started using them only recently as a simple wireless access point, wired to another openwrt router. I installed 19.07.0-rc2 and also tried NotTengoBattery v0.30.

Everything was working fine (apart from some minor ping latency issues) until I stumbled across transfer speed problems with Intel Centrino 6300 802.11n (3x3) wifi cards. Speeds were capped to 12-15 Mbps on different model Dell Windows 10 laptops on both 2.4 and 5 GHz bands even though wireless link speed is shown as 300 Mbps on 5 GHz band. Same for Intel 6205 (2x2) card which uses same windows wifi driver.

There are no speed problems when using older Intel 6200 card (uses older driver) and later 7260 N and AC cards (newer driver).

After reading this thread, I flashed older 19.07-r10293 snapshot (kernel 4.14.136, hostapd-common: 2018-12-02-c2c6c01b-6) and transfer speeds with Intel 6300 wifi card are back to normal. ie. not capped at 12-15 Mbps.

https://forum.openwrt.org/t/ipq40xx-ea6350-v3-as-wap-wifi-to-lan-latency/51623/26

I also quickly tested 19.07.0-rc1 with hostapd-common: 2018-12-02-c2c6c01b-9 still suffers from same problem.

This is my build of the Archer C7 v2 with hostapd 2.8.
openwrt-sysupgrade - Wetransfer download link
I already shared this with @systemcrash, please check the sha256 sum before flashing just in case:

sha256sum openwrt-19.07-snapshot-r10194+603-c53f62b111-ar71xx-generic-archer-c7-v2-squashfs-sysupgrade.bin 
3303618b3ed2d70caab11d7f23f76755303974bfbef4fb5463a40df49dd7b470  openwrt-19.07-snapshot-r10194+603-c53f62b111-ar71xx-generic-archer-c7-v2-squashfs-sysupgrade.bin

Please remember I don't have a Archer device so I can't really test this binary.

I think at this point we are seeing this issue on at least 3 different devices, so it's more likely related to hostapd rather than a specific card or device.

so why this is not a problem on other devices, other target? i have alot devices and this problem is only present on my zyxel 6617, this is the only device i have with this target, and ath10k

i think the problem here is more ath10k , ath10k-candela, or any ath10k

Ok, have tried your build. My results for 5 Ghz are at http://www.dslreports.com/speedtest/58319719. It works better than the results I was seeing on the snapshots after 11 Sep (seconds - See FS#2563 but it's still not great.

Here's my results for 18.06.5 - http://www.dslreports.com/speedtest/58319798 which are much better.

The big tell is ping consistency, as I noted earlier somewhere. Run from any computer via 5GHz connection and let it run for 20 or so seconds e.g.

ping 8.8.8.8

Ok, here's the ping results for 18.06.5

C:\Users\Warren>ping 8.8.8.8 -n 100

Pinging 8.8.8.8 with 32 bytes of data:
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=20ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=47ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=10ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=17ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=21ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=18ms TTL=55
Reply from 8.8.8.8: bytes=32 time=17ms TTL=55
Reply from 8.8.8.8: bytes=32 time=18ms TTL=55
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=18ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=17ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=20ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=22ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=18ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=19ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=18ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55

Ping statistics for 8.8.8.8:
    Packets: Sent = 100, Received = 100, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 10ms, Maximum = 47ms, Average = 14ms

The results for @hgblob's image:

C:\Users\Warren>ping 8.8.8.8 -n 100

Pinging 8.8.8.8 with 32 bytes of data:
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=10ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=24ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=18ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=21ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=21ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=17ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=22ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=22ms TTL=55
Reply from 8.8.8.8: bytes=32 time=17ms TTL=55
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=16ms TTL=55
Reply from 8.8.8.8: bytes=32 time=11ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=28ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=15ms TTL=55
Reply from 8.8.8.8: bytes=32 time=17ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=13ms TTL=55
Reply from 8.8.8.8: bytes=32 time=12ms TTL=55
Reply from 8.8.8.8: bytes=32 time=14ms TTL=55
Reply from 8.8.8.8: bytes=32 time=432ms TTL=55

Ping statistics for 8.8.8.8:
    Packets: Sent = 100, Received = 100, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 10ms, Maximum = 432ms, Average = 18ms

And finally the 19.07.0-rc2 image from the Openwrt download server

C:\Users\Warren>ping 8.8.8.8 -n 100

Pinging 8.8.8.8 with 32 bytes of data:
Reply from 8.8.8.8: bytes=32 time=110ms TTL=55
Reply from 8.8.8.8: bytes=32 time=126ms TTL=55
Reply from 8.8.8.8: bytes=32 time=27ms TTL=55
Reply from 8.8.8.8: bytes=32 time=42ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=231ms TTL=55
Reply from 8.8.8.8: bytes=32 time=45ms TTL=55
Request timed out.
Request timed out.
Reply from 8.8.8.8: bytes=32 time=708ms TTL=55
Reply from 8.8.8.8: bytes=32 time=424ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=208ms TTL=55
Reply from 8.8.8.8: bytes=32 time=753ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=372ms TTL=55
Reply from 8.8.8.8: bytes=32 time=35ms TTL=55
Reply from 8.8.8.8: bytes=32 time=100ms TTL=55
Reply from 8.8.8.8: bytes=32 time=210ms TTL=55
Reply from 8.8.8.8: bytes=32 time=55ms TTL=55
Reply from 8.8.8.8: bytes=32 time=206ms TTL=55
Request timed out.
Request timed out.
Reply from 8.8.8.8: bytes=32 time=240ms TTL=55
Reply from 8.8.8.8: bytes=32 time=262ms TTL=55
Reply from 8.8.8.8: bytes=32 time=139ms TTL=55
Reply from 8.8.8.8: bytes=32 time=211ms TTL=55
Reply from 8.8.8.8: bytes=32 time=232ms TTL=55
Reply from 8.8.8.8: bytes=32 time=304ms TTL=55
Reply from 8.8.8.8: bytes=32 time=464ms TTL=55
Reply from 8.8.8.8: bytes=32 time=62ms TTL=55
Reply from 8.8.8.8: bytes=32 time=277ms TTL=55
Reply from 8.8.8.8: bytes=32 time=281ms TTL=55
Reply from 8.8.8.8: bytes=32 time=230ms TTL=55
Reply from 8.8.8.8: bytes=32 time=640ms TTL=55
Reply from 8.8.8.8: bytes=32 time=399ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=259ms TTL=55
Reply from 8.8.8.8: bytes=32 time=28ms TTL=55
Reply from 8.8.8.8: bytes=32 time=111ms TTL=55
Reply from 8.8.8.8: bytes=32 time=98ms TTL=55
Reply from 8.8.8.8: bytes=32 time=126ms TTL=55
Reply from 8.8.8.8: bytes=32 time=286ms TTL=55
Reply from 8.8.8.8: bytes=32 time=221ms TTL=55
Reply from 8.8.8.8: bytes=32 time=67ms TTL=55
Reply from 8.8.8.8: bytes=32 time=94ms TTL=55
Reply from 8.8.8.8: bytes=32 time=115ms TTL=55
Reply from 8.8.8.8: bytes=32 time=94ms TTL=55
Reply from 8.8.8.8: bytes=32 time=152ms TTL=55
Reply from 8.8.8.8: bytes=32 time=58ms TTL=55
Reply from 8.8.8.8: bytes=32 time=92ms TTL=55
Reply from 8.8.8.8: bytes=32 time=224ms TTL=55
Reply from 8.8.8.8: bytes=32 time=124ms TTL=55
Reply from 8.8.8.8: bytes=32 time=204ms TTL=55
Reply from 8.8.8.8: bytes=32 time=155ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=312ms TTL=55
Reply from 8.8.8.8: bytes=32 time=423ms TTL=55
Reply from 8.8.8.8: bytes=32 time=151ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=333ms TTL=55
Request timed out.
Request timed out.
Request timed out.
Reply from 8.8.8.8: bytes=32 time=23ms TTL=55
Reply from 8.8.8.8: bytes=32 time=424ms TTL=55
Reply from 8.8.8.8: bytes=32 time=261ms TTL=55
Reply from 8.8.8.8: bytes=32 time=130ms TTL=55
Reply from 8.8.8.8: bytes=32 time=1059ms TTL=55
Reply from 8.8.8.8: bytes=32 time=344ms TTL=55
Reply from 8.8.8.8: bytes=32 time=369ms TTL=55
Reply from 8.8.8.8: bytes=32 time=237ms TTL=55
Reply from 8.8.8.8: bytes=32 time=160ms TTL=55
Reply from 8.8.8.8: bytes=32 time=398ms TTL=55
Reply from 8.8.8.8: bytes=32 time=372ms TTL=55
Reply from 8.8.8.8: bytes=32 time=380ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=231ms TTL=55
Reply from 8.8.8.8: bytes=32 time=225ms TTL=55
Reply from 8.8.8.8: bytes=32 time=152ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=459ms TTL=55
Reply from 8.8.8.8: bytes=32 time=577ms TTL=55
Reply from 8.8.8.8: bytes=32 time=500ms TTL=55
Reply from 8.8.8.8: bytes=32 time=218ms TTL=55
Reply from 8.8.8.8: bytes=32 time=297ms TTL=55
Reply from 8.8.8.8: bytes=32 time=320ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=597ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=78ms TTL=55
Reply from 8.8.8.8: bytes=32 time=304ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=154ms TTL=55
Request timed out.
Reply from 8.8.8.8: bytes=32 time=27ms TTL=55
Reply from 8.8.8.8: bytes=32 time=102ms TTL=55
Reply from 8.8.8.8: bytes=32 time=25ms TTL=55
Reply from 8.8.8.8: bytes=32 time=71ms TTL=55
Reply from 8.8.8.8: bytes=32 time=123ms TTL=55

Ping statistics for 8.8.8.8:
    Packets: Sent = 100, Received = 81, Lost = 19 (19% loss),
Approximate round trip times in milli-seconds:
    Minimum = 23ms, Maximum = 1059ms, Average = 243ms

And for completeness here is a really ugly bufferbloat speedtest for the 19.07.0-rc2 image: http://www.dslreports.com/speedtest/58320732

The change to hostapd 2.9 is obviously a big problem here. However, the hostapd 2.8 version that @hgblob did still exhibits higher than normal ping latency under load (bufferbloat) indicating there is something going on in hostapd 2.8 that the changes in 2.9 push right over the edge.

One more thing that I did to fix throughput for my wireguard VPN running on the router was to switch the scaling governor to performance. The ondemand governor was basically not switching fast enough through the DVFS table and for whatever reasons the wireguard throughput was very low.

echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor 

but depending on the system your router might run a bit(or more hotter). It adds about +2oC operating temp.

I think Qualcomm(Atheros?) is affected, Archer C7 v2 is a ath9k device.

https://openwrt.org/toh/hwdata/tp-link/tp-link_archer_c7_ac1750_v2.0

ath9k is my love and i cannot confirm that, i think i have over 20 ath9k devices

Looks like there are some updates your original bug report.
FS 2679

I will try the precompiled image for EA6350v3 offered by Petr Štetiar. It contains very latest hostapd 2.9.
TESTING! hostapd: update to hostap_2_9-542-g33c8a10498c1

Update: Sadly, no improvement when using test image for EA6350 v3. Downloads still stuck at < 15 Mbps.

I also tested the commit on NBG6617 and I didn't see any improvements either.

Seems like this patch fixes the problem, or at least it fixes it on ipq4019.