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How do you diagnose slow computing time issues on the Pi?

I have Ubuntu 16.04 installed on a Raspberry Pi 3. All Ubuntu package updates are installed, and I've installed the most recent Pi firmware. However, for simply operations, like extracting small tarballs or installing a package, the Pi can take 30 minutes or more. What's really odd is that if I run top or htop, it shows no CPU activity and very little memory usage during this time, so I'm at a loss for why the operations are taking so long.

I've read the SD card can be slow, so I measured it's write speed by running:

dd if=/dev/zero of=/tmp/test.img bs=1M count=100

three times, and the MB/sec readings were 50, 11, 23, for an average of 28 MB/sec, which isn't stellar but wouldn't explain a 1 MB tarball taking minutes to extract.

I tried using raspi-config to overclock the Pi, but it told me that, "This pi cannot be overclocked", so I guess that's not an option.

I have a small stick-on heatsink attached to the Pi's main processor, and I even bought a tiny fan to blow air over it, so I don't think it's overheating.

What are other things I can do to determine why my Pi is behaving so slowly and speed it up?

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    You are swapping. Ubuntu is a beast. Check free physical memory with top. – user2497 Jun 19 '17 at 11:43
  • top is showing no swap in use. To free up memory, what services that come enabled by default in Ubuntu can I safely remove on the Pi? – Cerin Jun 19 '17 at 17:12
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    Measure the temperature of the CPU and RAM chips. It's best to add a dab of thermal paste to the temperature probe. If you don't have a thermometer, use your finger. The CPU will clock down if overheated. You can overclock it to hell and back in /boot/config.txt, and as long as you keep temperature below 80°, it won't clock down. – user2497 Jun 19 '17 at 20:42

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