I'm getting high and variable latency with this wifi. If I plug in a usb wifi dongle, I get ~15 +/- 0.1 ms ping to 8.8.8.8. With the in built wifi, I get anywhere from 50 to 1000+ ms latency. I'm running Ubuntu 14.04. Based on others issues with this wifi card, I updated to an upstream kernel, version 3.18.3, which enabled wifi, but still high latency.
Let me know if any additional information is needed.
Please attach dmesg output.
Created attachment 165941 [details] dmesg output
please try to disable power save. sudo iw wlan0 set power_save off
That has worked! Is there a way to permanently disable power save, or do I need to turn it off at every boot? Also, will this change be pushed into the upstream kernel, at least for this wifi card?
disabling power save should not be pushed to upstream kernel. If power save causes high latency in Tx, then there is a bug. Power save can cause issues in Rx, not in Tx. You can add a module parameter for iwlmvm: options iwlmvm power_scheme=1
The only way I have been able to reproducibly test high latency is via ping, both pinging from this problem machine to other machines and pinging from other machines to this machine. From my understanding, either way uses both Tx and Rx. Is there a way to check only one or the other? And even if power save is causing issues in only Rx, isn't that also a bug?
(In reply to anuppari from comment #7) > The only way I have been able to reproducibly test high latency is via ping, > both pinging from this problem machine to other machines and pinging from > other machines to this machine. From my understanding, either way uses both > Tx and Rx. Is there a way to check only one or the other? > The question here is where you do your ping command. You need to ping from the machine that has the 7260. > And even if power save is causing issues in only Rx, isn't that also a bug? No - that's the way WiFi works
If I ping from the machine with the 7260, I get latency issues (without power save off). I also get high ping time if I ping the 7260 machine from another machine. So it seems to be a problem both ways, at least with power save on. With power save off, it works fine both ways. How do I set that module parameter? I tried running that command in the terminal but there is no options command. Does that line need to be added to a file?
can you a more recent firmware? curl https://git.kernel.org/cgit/linux/kernel/git/iwlwifi/linux-firmware.git/plain/iwlwifi-7260-10.ucode?id=c3d350ee05a8cf15c119af0fd1a60cd8595379c2 > iwlwifi-7260-10.ucode sudo cp iwlwifi-7260-10.ucode /lib/firmware/ reboot I'd like to know if this firmware will solve your latency problems with power save enabled.
Latency is still present with the new firmware.
can you please share your dmesg with the new firmware? Also - I'd like to see the output of iw wlan0 link
Created attachment 166281 [details] dmesg output with new firmware
Created attachment 166291 [details] link info
all seems fine here... please paste the output of ping when it is run from the 7260. Thanks.
Created attachment 166301 [details] ping with power save off
Created attachment 166311 [details] ping with power save on
Created attachment 166321 [details] ping local server with power save off
Created attachment 166331 [details] ping local server with power save on
I added pinging a local server. This really shows the difference with/without power management
you were talking about 1000ms, here I can ~60ms... It is not the same... I can't say that these number are great but for sure, no real bug here. That can also be related to the AP. Closing this bug.
I think the new firmware helped a little with the latency. But you can see when pinging the local server, there is an order of magnitude difference between with and without power management (~1 ms to ~60). That is not insignificant.