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Natanael Copa

Compile time of same linux kernel on different hardware:

- milkv pioneer: 0h 52m 20s
- hifive premiere: 3h 32m 20s

The pioneer has 64 CPU cores while the premiere only has 4.

@ncopa
That's really interesting... I would have expected a more linear decrease in procecssing time as, from what I understand, the kernel compile should scale horizontally pretty well...

I/O bottleneck or maybe memory (swapping/paging)?

@Brett_E_Carlock @ncopa

Amdahl's Law will always get you on highly parallel tasks, there is always some slow serial bottleneck

@Brett_E_Carlock @ncopa

I looked for more about Amdahl's Law and also found Gustafson's Law - the idea that as systems get more parallel, instead of trying to minimize the time spent on a task, people will expand the task to fill the available parallel capacity.

vielmetti.typepad.com/logbook/

so if it's OK to test a system in an hour, and suddenly you get 2x the number of cores to work with, you'll tend to expand the number of tests to run rather than seek incremental improvements in runtime.