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DragonFly kernel List (threaded) for 2004-04
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Re: pipe testing and kernel copyin/copyout/bcopy performance

From: Dave Leimbach <leimySPAM2k@xxxxxxx>
Date: 29 Apr 2004 15:12:28 -0500

Hiten Pandya <hmp@xxxxxxxxxxxxx> writes:

> 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@xxxxxxxxxxxxx

I've also read something about caches not being updated by using SSE 
instructions such that if you refer to the memory you just copied that the 
wins for having used SSE in the copy are much diminished.


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