[tobyhinloopen]

Every time I try to increase the performance of my software by using multiple cores, I need a lot of cores to compensate for the loss of per-core efficiency. Like, it might run 2-3 times as fast on 8 cores.

I'm sure I've been doing it wrong. I just had better luck optimizing the performance per core rather than trying to spread the load over multiple cores.

[viraptor]

Or your task needs the overhead to sync and read/write data. Only you can tell really with access to code/data, but 3x speed on 8x cores may well be the theoretical maximum you can do for this specific thing.

[pjc50]

Synchronization overhead is more than people think, and it can be difficult to tell when you're RAM/cache-bandwidth limited. But it makes a difference if you can make the "unit of work" large enough.