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I am SSHed into the Pi using PuTTY on a Windows computer. Everything works fine as expected but if I don't do anything on the Pi for roughly 5-10 minutes and then come back to it there is some weird delay (of about 5-10 seconds) before the SSH window becomes responsive again. This means for those 5-10 seconds, it does not take any inputs from my keyboard or selects the previous command if I push the up arrow on my keyboard.

I don't think this issue is an SSH problem necessarily. The same symptoms above seem to happen when I send a POST request to a webserver running on the Pi.

I have tried:

  • Disabling power management on the network card.
  • Disabling Bluetooth (Don't need it anyway, disabled to save power.)
  • And everything that came up online regarding possible similar issues (although nothing worked)
  • Seeing if it is overheating. Its not.

The Pi is running Stretch Raspbian (Linux raspberrypi 4.14.34+ #1110)

I'll attach the log file (var/log/messages) but I can't seem to find anything obvious in it: https://pastebin.com/YfUV9aF0

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  • may be a screensaver or may be sleep mode
    – jsotola
    Jun 23, 2018 at 22:15
  • @jsotola I forgot to mention it is entirely headless. Care to elaborate as to how I could fix the issues you mentioned?
    – Erozionn
    Jun 24, 2018 at 23:04
  • it was just an idea that popped into my head ... i do not know how to check if either a screen saver or sleep/power-save mode may be active on your RPi
    – jsotola
    Jun 24, 2018 at 23:28
  • Maybe it isn't the raspi. Instead it could be the windows computer with putty doing this delay.
    – Ingo
    Jun 26, 2018 at 8:16
  • As mentioned before, it also happens when I make an HTTP request to the pi. I think that rules out it being an issue with putty/windows/ssh.
    – Erozionn
    Aug 27, 2018 at 19:29

2 Answers 2

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We use hundreds of Pis in a production environment (as a replacement for thin clients). We've noticed a similar problem. It happens on either ethernet or wireless. After about 5-10 minutes of inactivity a new request to the server can result in a delay anywhere from 30 seconds to 2 minutes.

This only seems to happen on the 4.14 kernel, does not happen on 4.9. Because of this we can't use any of the new 3B+ Pis yet.

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My Rpi0 runs on a Kali Linux with kernel v4.4.50+ and I have never experienced this issue.

All I can suggest is to SSH into you Rpi0/W, run the top utility, and let it sit for 5-10 minutes. Observe the top activity when trying to access your Rpi0/W to see what happens that causes the delay.

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