3 ms·

So the compiled kernel potentially misses out on instructions that newer CPUs support?

• kjeetgill 7y ago
  Yes. This is why distros like Gentoo and others prefer building from source. Then you can enable as many architecture specific extensions your compiler supports. I don't know how much of a difference this makes in practice however.
  • wtallis 7y ago
    The justification for dropping 386 support was that it was a maintenance burden specifically for SMP locking primitives, IIRC. Dropping support for other 90s microarchitectures would mean not needing a workaround for the Pentium F00F bug, and having access to SIMD and prefetch instructions that can make things like a memcpy more efficient.
    • vardump 7y ago
      > SIMD and prefetch instructions that can make things like a memcpy more efficient. Or just use REP MOVS. Modern CPUs recognize it and do optimal memory copy internally. Prefetch instructions are rarely beneficial, and often cause worse performance. Edit: Apparently AMD Ryzen lacks REP MOVS optimization. SIMD based memcpy performs the best on it. (Intel supports REP MOVS optimization since Ivy Bridge.)