[SOLVED] Suddenly gets very slow, despite very low CPU usage

[outhudd9]

Often my Odroid C2 will almost freeze up. Running everything very slowly.

As an example, I've noticed then when apt install is unpacking a package. It seems to stay at the same point for a very long time, and when I do htop, I see only 1 or 2% CPU usage, nothing really happening. Memory isn't full and Swap is not being used.

Anyway I can check what this bottleneck is? Using Ubuntu 16.04.4 and...

Linux odroid64 3.14.79-117 #1 SMP PREEMPT Tue Jan 2 23:46:30 BRST 2018 aarch64 aarch64 aarch64 GNU/Linux

Maybe I should check SD r/w speed?

[rooted]

Could you post the output of dmesg to pastebin after this happens?

Also verify your storage r/w speed.

[crashoverride]

As an example, I've noticed then when apt install is unpacking a package. It seems to stay at the same point for a very long time, and when I do htop, I see only 1 or 2% CPU usage, nothing really happening. Memory isn't full and Swap is not being used.

apt is very I/O intensive. This likely means that the storage (SD card) is the bottleneck. Try using a different SD card or a higher rated (A1) card.

[outhudd9]

Thanks, I don't see anything relevant with dmesg.

I'll try a few benchmarks to test different SD cards and see if that's the problem.

[crashoverride]

Its also worth noting that apt runs in two phases: download and install. The information displayed during operation will indicate what its doing. The download phase may be bottlenecked by the network while the install phase may be bottlenecked by storage.

[outhudd9]

As an example, I've noticed then when apt install is unpacking a package. It seems to stay at the same point for a very long time, and when I do htop, I see only 1 or 2% CPU usage, nothing really happening. Memory isn't full and Swap is not being used.

apt is very I/O intensive. This likely means that the storage (SD card) is the bottleneck. Try using a different SD card or a higher rated (A1) card.

Thanks for this.

The SD card was the problem here. I got an A1 rated Sandisk 32GB and the difference is like night and day. Much much faster now all round. Thanks!