Karel Kulhavy <clock@atrey.karlin.mff.cuni.cz> said:
> I realized some varieties of Pentium can memcpy fater by loading
> MMX registers and then unloading them. Is it meaningful to use this
> for optimizing memcpy actions used by kernel? Could SSE help on processors
> which support SSE?
MMX registers are the FP registers, so you'd clobber them (FP in kernel is
off-limits in part for this reason). Besides, I remember that switching
into/out of MMX mode is _very_ costly, so much so that this doesn't buy you
anything unless you do very large copies. And those are rare enough not to
bother.
> Where is the memcpy in kernel placed? In kernel sources, or in libc?
The kernel doesn't use libc at all.
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This archive was generated by hypermail 2b29 : Mon May 15 2000 - 21:00:20 EST