Re: X15 alpha release: as fast as TUX but in user space (fwd)

From: dean gaudet (
Date: Sun Apr 29 2001 - 11:21:31 EST

On Sun, 29 Apr 2001, Jeff Garzik wrote:

> "H. Peter Anvin" wrote:
> > We discussed this at the Summit, not a year or two ago. x86-64 has
> > it, and it wouldn't be too bad to do in i386... just noone did.
> It came up long before that. I refer to the technique in a post dated
> Nov 17, even though I can't find the original.
> Initiated by a post from (iirc) Dean Gaudet, we found out that
> gettimeofday was one particular system call in the Apache fast path that
> couldn't be optimized well, or moved out of the fast path. After a
> couple of suggestions for improving things, Linus chimed in with the
> magic page suggestion.

heheh. i can't claim that i was the first ever to think of this. but
here's the post i originally made on the topic. iirc a few folks said
"security horror!"... then last year ingo and linus (and probably others)
came up with a scheme everyone was happy with.

i was kind of solving a different problem with the code page though -- the
ability to use rdtsc on SMP boxes with processors of varying speeds and


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