FreeBSD 5.2 v/s FreeBSD 4.9 MFLOPS performance (gcc3.3.3 v/sgcc2.9.5)

[Juan Tumani]

Wes,

I patched in the patch shown below and it didn't fix the problem, it
only changed the frequency of the spikes to 32 on/off.  Please see
the second chart at this URL:

http://www.employees.org/~rsargent/flops/charts2.html

Did you run the script [long enuf] to see what frequency you experience with 
the kern
pacthed on your system?

JT


>From: Wes Peters <wes at softweyr.com>
>To: des at des.no (Dag-Erling Smørgrav),Alexandr Kovalenko 
><never at nevermind.kiev.ua>
>CC: freebsd-hackers at freebsd.org, Juan Tumani <jtumani55 at hotmail.com>
>Subject: Re: FreeBSD 5.2 v/s FreeBSD 4.9 MFLOPS performance (gcc3.3.3 
>v/sgcc2.9.5)
>Date: Mon, 16 Feb 2004 03:52:16 -0800
>
>On Sunday 15 February 2004 12:46, Dag-Erling Smørgrav wrote:
> > Alexandr Kovalenko <never at nevermind.kiev.ua> writes:
> > > Could you please explain me this? Result is fully reproduceable. 
>Please
> > > note, that the only difference is the output file name. Even resulting
> > > files match bit-to-bit. [...]
> >
> > Definitely some kind of alignment problem, but it only shows up at
> > some optimization levels and not others.
>
>I've tested the patch Dan mentioned before and the results were 
>astonishing.
>Running the flops.c 1.2 program in a loop, lengthening the environment 
>string
>by one byte each time, I get 8 successive runs of fast, then 8 successive
>runs of slow, where fast and slow vary between 650 and 990 mflops.  With 
>the
>patch, the performance is always 990, within a few percent.
>
>Should I commit this?
>
>RCS file: /big/ncvs/src/sys/kern/kern_exec.c,v
>retrieving revision 1.235
>diff -u -w -r1.235 kern_exec.c
>--- kern_exec.c 28 Dec 2003 04:37:59 -0000      1.235
>+++ kern_exec.c 11 Feb 2004 16:47:28 -0000
>@@ -1014,6 +1014,15 @@
>                  */
>                 vectp = (char **)(destp - (imgp->argc + imgp->envc + 2) *
>                     sizeof(char *));
>+
>+       /*
>+        * Align stack to a multiple of 0x20.
>+        * XXX vectp has the wrong type; we usually want a vm_offset_t;
>+        * the suword() family takes a void *, but should take a 
>vm_offset_t.
>+        * XXX should align stack for signals too.
>+        * XXX should do this more machine/compiler-independently.
>+        */
>+       vectp = (char **)(((vm_offset_t)vectp & ~(vm_offset_t)0x1F) - 4);
>
>         /*
>          * vectp also becomes our initial stack base
>
>
>--
>          "Where am I, and what am I doing in this handbasket?"
>
>Wes Peters                                                  Softweyr LLC
>wes at softweyr.com                                    http://softweyr.com/
>
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