DietPi-Config | Add Stress Test

[Fourdee]

As per @zone22's suggestion: https://github.com/Fourdee/DietPi/issues/489

Tests for stability. Must test:

• CPU
• Filesystem IO
• RAM

[Fourdee]

dietpi-config > tools > Stress Test

stress -c $cores -i 2 -m $cores --vm-bytes "$memory_per_thread"M -d 1 -t "$duration"s 

And it works, just killed my overclocked RPi 3 lol

[k-plan]

@Fourdee

nice work! 😄 👍

_Testing result on NanoPi NEO:_