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Date:	Fri, 15 Dec 2006 17:16:07 +0100
From:	Magnus Holmgren <lear AT algonet DOT se>
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Subject:	Re: Cygwin slower on one computer
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Magnus Holmgren wrote:

 > I'm trying to figure out why Cygwin build things so much slower on one
 > computer I have. We're talking about more than 3 times slower on a
 > computer that ought to be a bit faster (Athlon64 at 2.2-2.4 GHz,
 > compared to a  Pentium M at 1.8 GHz).

After some more digging - and a bit of feedback off-list - I get the 
feeling (in the cases I've noticed at least) that the speed difference 
is mainly explained by the following reasons (in no particular order):

* fork is expensive.
* vfork is just a wrapper for fork on cygwin.
* fork is much more expensive on AMD than on Intel.

The third one is the one I'm most unsure about, as I only really have 
data about one Intel architecture (the Pentium M). But on the AMD 
system, the page fault delta (as reported by Process Explorer) during a 
build is a little more than 10,000 per second, while on the Intel 
system, the page fault delta can go to 30,000 per second.

(Anyone who knows how SFU implements (v)fork? :)

    Magnus

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