svn commit: r201545 - head/sys/geom/raid3

[Ivan Voras]

2010/1/5 Alexander Motin <mav at freebsd.org>:
> Author: mav
> Date: Tue Jan  5 02:06:05 2010
> New Revision: 201545
> URL: http://svn.freebsd.org/changeset/base/201545
>
> Log:
>  Slightly optimize XOR calculation.

Linux has an interesting approach to RAID XOR operations - they
calculate at boot time which method is faster, from a set of i386,
MMX, SSE and the like and then use it for what appears to be every
context requiring fast XORs.

E.g.
http://fxr.watson.org/fxr/source/arch/x86/include/asm/xor_64.h?v=linux-2.6

(I know SIMD instructions would require a FP-enabled kernel, I'm just
pointing out an interesting idea)