Re: It's 1997. Do you know where your scheduler is?

David Greene <greened@eecs.umich.edu>
4 Jan 1998 20:51:20 -0500

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Related articles
It's 1997. Do you know where your scheduler is? djb@cr.yp.to (D. J. Bernstein) (1997-12-19)
Re: It's 1997. Do you know where your scheduler is? chase@world.std.com (David Chase) (1997-12-23)
Re: It's 1997. Do you know where your scheduler is? djb@cr.yp.to (D. J. Bernstein) (1997-12-29)
Re: It's 1997. Do you know where your scheduler is? greened@eecs.umich.edu (David Greene) (1998-01-04)
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From: David Greene <greened@eecs.umich.edu>
Newsgroups: comp.compilers
Date: 4 Jan 1998 20:51:20 -0500
Organization: University of Michigan EECS
References: 97-12-170
Keywords: architecture, performance, optimize

D. J. Bernstein <djb@cr.yp.to> wrote:
: > which release of gcc,


: It really doesn't matter. Here are some Pentium cycle counts for the
: same hand-scheduled 256-point complex FFT code:


: 23085 (best) gcc 2.7.2.1 -O1 -fo-f-p
: 41913 gcc 2.7.2.1 -O6 -fo-f-p
: 47258 egcs 1.00 -O6 -fo-f-p -mpentiumpro
: 56383 egcs 1.00 -O6 -fo-f-p -mpentium
: 56860 (worst) egcs 1.00 -O6 -fo-f-p


Has anyone tried egcs? It apparently contains a Pentium scheduler.
I don't know whether it does PPro.


: The Pentium Pro, as you noted, is a very different chip. Scheduling
: code badly for the Pentium Pro would take quite a bit of effort.


Unless you ignore the 4-1-1 decode, which is (IIRC) the main
bottleneck (once stuff is in from the cache/memory, that is...).


                                                                                            -Dave
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