C6 uses the atheros ath10k open source driver.... The performace of open source driver is not equal to the closed source driver that came with the original firmware. But is improving every day 
You can try the last master of openwrt. I could get a substantial increase in C6 wifi with the last ath10k driver.
Try using flow_offloading too.
Hello @gaspare
Thanks for looking into this.
Since i am a beginner in OpenWRT I used the firmware in this page: https://openwrt.org/toh/tp-link/tp-link_archer_c6_v2
I am not expert in this so can you please let me know which firmware should I use here? Or do I only need to upgrade the drivers? Can you please walk me through this?
yes I have already used software flow_offloading. Before I used it it was even worse than this, I was getting 100Mbps but now it is the double after enabling it. Via cable I get 450 Mbps
Regards,
Try the devepment snapshots... See if its better for your needs...
Just know that those are development ones... Just for tests, not for production... Its just to analyze if you have an improvement....
One of the main differences is that the master build do not have the Luci gui... so, you have to do with ssh in the router....
Read this first: https://openwrt.org/releases/snapshot
You cant download the last snapshot for C6 in here:
https://downloads.openwrt.org/snapshots/targets/ath79/generic/
Hello Gaspare,
I have tried to flash one of the Snapshots successfully and upgraded the firmware accordingly but the WIFI is still the same, no change at all 
Is there going to be any improvement in the future? I think that I will go back to the stock firmware for now since I am not getting the full speed using OpenWRT which is sad to me
Thanks alot for your help everyone
Regards,
Anyone? Can someone help here? Should I try different builds?
Try build from here, Recommended build 30 variant2
Hi.
How is this measurment done? You need to run iperf3 on computer wired on LAN side and iperf3 client on mobile device to truly measure throughput.
Running iperf3 server in router itself will lead to low results as SoC is not powerful enought and running both client and server on WiFi will cut speed to one third at best (as there will be lot's of collisions).
My C7 tops out around 500Mbit on 80Mhz VHT (albeit with SoC overclocked to 1GHz).
Hey,
TP-Link AC1200 Archer C6 on latest build. Also topping at about ~220Mbit .
It improved after it was on ~120Mbit when I enabled flow_offloading. But its not reaching the speed I get wired for the internet which is 300Mbit.
The fact that a setting made such an improvement makes me suspect there might be another setting that would improve it.
Also tried the developer snapshot, that broke luci and after fixing it saw no improvement.
Hi. Is this speed issue still persistent in 19.07.6 build?
Can somebody test snapshot build, if is something changed after this commit:
Thx!
Yes, it still persists. I have a max. rate of 150Mbit on 5Ghz instead of 600Mbit using stock firmware. By the way it is also commented in the description page and C6 uses ath79 driver. So OpenWrt is not really good usable with that difference. Does somebody know if a fixed is planned?
I do get around 210 mbit/s with nat and around 270 mbit/s without nat on 5ghz on an archer c6 v2 eu with 19.07.6 openwrt. I was told, that this is the price for using open source drivers. And for me that performance is sufficient. If I need it faster, I use a cable...
With newest snapshot the performance issue is solved. Perhaps interesting for everybody.
What throughput do you get now ? Does the snapshot use ath10k or ath10k-ct ?
45 Mbyte/s Up- and Download. Did not know the driver. Router is packed away. I can check next week, will mount it on monday.
Actual max. reachable wireless performance in 19.07.7
Tested with iperf3 TCP behind the router
VHT80
5640Mhz
bridge mode
CPU load at 100 percent during the test (in Archer C6v2 router)
DOWN: 250-300 Mbit/s
UP: 350-400Mbit/s
Snapshot is much better in AP mode. Router performance should be slower because of the slow CPU.
Seems to be ath10k-ct
ath10k 5.10 driver, optimized for CT firmware, probing pci device: 0x56.
[ 12.694725] ath10k_pci 0000:00:00.0: enabling device (0000 -> 0002)
[ 12.701549] ath10k_pci 0000:00:00.0: pci irq legacy oper_irq_mode 1 irq_mode 0 reset_mode 0
[ 12.722379] random: crng init done
[ 15.376898] ath10k_pci 0000:00:00.0: qca9888 hw2.0 target 0x01000000 chip_id 0x00000000 sub 0000:0000
[ 15.386483] ath10k_pci 0000:00:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 0
[ 15.406541] ath10k_pci 0000:00:00.0: firmware ver 10.4b-ct-9888-fW-13-5ae337bb1 api 5 features mfp,peer-flow-ctrl,txstatus-noack,wmi-10.x-CT,ratemask-CT,regdump-CT,txrate-CT,flush-all-CT,pingpong-CT,ch-regs-CT,nop-CT,set-special-CT,tx-rc-CT,cust-stats-CT,txrate2-CT,beacon-cb-CT,wmi-block-ack-CT,wmi-bcn-rc-CT crc32 59e741e7
[ 15.748192] ath10k_pci 0000:00:00.0: failed to fetch board data for bus=pci,bmi-chip-id=0,bmi-board-id=20 from ath10k/QCA9888/hw2.0/board-2.bin
[ 15.762374] ath10k_pci 0000:00:00.0: board_file api 1 bmi_id 0:20 crc32 f8e90c54
I can confirm lower performance.
OWRT 21.02-rc1 already has this CT driver (speed is same as with today snapshot).
Compared with iPerf3:
Original FW:
1 connection - 216/206 Mbit
20 connections - 385/460 Mbit
OpenWRT:
1 con - 190/128 Mbit
20 con - 266/350 Mbit.
What is weird, that with speedtest.net I don't get more then around 140 Mbit (over cable I have 300Mbit without problem). Original FW didn't have this problem.
Also OWRT has problem with Full duplex. On original FW I had 190/268 Mbit when running iPerf3 in both directions (not using the switch, but really running two instances of iPerf3).
With OWRT I got 320/12.
Same problem, i'm using OWRT 21.02-rc1.
RJ45: 600Mbps D/U
WIFI AC: ISP Router about 600 Mbps D/U
Archer C6 300Mbps D/U
Seems speed is capped to 300 Mbps, i don't know it is a driver problem or is software capped, but is crazy.