How to make a foreign function run as fast as possible in Windows?

[jfong at ms4.hinet.net]

Chris Angelico at 2016/10/1 11:25:03AM wrote:
> What's it doing? Not every task can saturate the CPU - sometimes they
> need the disk or network more.
> 
This function has no I/O or similar activity, just pure data processing, and it takes less than 200 bytes of data area to work with.

My CPU is an i3 (4 threads/2 cores). I suppose after this job was assigned to run on a particular core, the OS shouldn't bother it by other system related tasks anymore. If it does, won't be this OS designed stupidly?

I was puzzled why the core has no 100% usage? Why always has some percentage of idle?

--Jach