pipe testing and kernel copyin/copyout/bcopy performance

[Hiten Pandya]

Matthew Dillon wrote:

    Just to let people know, in case anyone is wondering why I have been so
    quiet lately :-)
    I've been running some major pipe benchmarks to compare various pipe 
    optimizations as part of a paper (FreeBSD's) Alan Cox and I are writing.

    At the same time I've delved deeply into the AMD64 and have been working
    on optimizing the kernel bcopy, memcpy, copyin, and copyout to use
    XMM instructions when possible.
	Didn't you mention to me something about FPU context switch
	overhead?  Secondly, wouldn't the XMM based copyin, bcopy etc
	make small transfers slow?
		-Hiten
		hmp at xxxxxxxxxxxxx