Quentin Garnier wrote:
> Le Mon, 21 Jun 2004 15:33:53 -0400
>
> Thor Lancelot Simon a ecrit :
> > On Mon, Jun 21, 2004 at 07:27:16PM +0000, Charles M. Hannum wrote:
> > > Adding extra memory requirements and startup overhead for EVERY
> > > SINGLE EXEC() is not a reasonable tradeoff.  This is definitely a
> > > non-starter.
> >
> > How much memory (and overhead) are we talking about here?  Can we get a
> > measurement of this?
> >
> > Clearly, if it were one byte, and one nanosecond, this change would be
> > a win; if it's 100 kilobytes, and 100ms, it would be a lose.  But the
> > added functionality does seem useful (after all, it lets us change libs
> > on the basis of any sysctl node, and most ports expose a lot more MD
> > nodes, including nodes that could be used to select optimized
> > libraries, than the loader actually knows about now) and eliminating
> > users of the old sysctl interface seems like a win, too, since it's
> > deprecated and a maintenance hassle.
>
> I've done a few quick and dirty tests.  Host is a NetBSD/i386 Celeron
> 2.6GHz with 512MB of memory.
>
> % ls -l /libexec/ld.elf_so*
> -r-xr-xr-x  1 root  wheel  69070 Jun 21 22:26 /libexec/ld.elf_so
> -r-xr-xr-x  1 root  wheel  57641 Jun 21 22:02 /libexec/ld.elf_so.2
>
> The smaller is the unpatched one.
>
> test.c is just 'int main() { exit(0); }'.  I compiled three versions of
> it, one just compiling the file (test), another adding -lm (testm).  On
> i386, libm387 is conditionally loaded upon value of machdep.fpu_present,
> so I compiled a third version adding both -lm and -lm387 to be used when
> ld.so.conf is empty (thus unconditionally loading libm387, as it would
> actually happen on this host).
>
> time measures the following command:
>
> sh -c 'for i in `jot 100000 1`; do ./test; done'
>
> With standard /etc/ld.so.conf:
>
>     test          -> 62.95s user  73.99s system 104% cpu 2:10.64 total
>     test+sysctl   -> 63.53s user  74.01s system 104% cpu 2:11.24 total
>     testm         -> 78.15s user  93.27s system 103% cpu 2:45.15 total
>     testm+sysctl  -> 84.50s user 102.15s system 103% cpu 2:59.92 total
>
> With empty /etc/ld.so.conf:
>
>     test          -> 60.04s user  69.71s system 105% cpu 2:03.56 total
>     test+sysctl   -> 60.87s user  70.70s system 105% cpu 2:05.17 total
>     testmm        -> 76.06s user  89.23s system 103% cpu 2:39.25 total
>     testmm+sysctl -> 76.20s user  90.05s system 104% cpu 2:39.68 total
>
> The result shows a 8.9% increase in loading time when sysctl is actually
> used (I tried a second run and got 7%, so it should be around those two
> values).

It reminds me of switch to dynroot of the base system in the past. Our 
dynroot binaries are 3-5x higher in load time cost after the switch. 8.9% 
sounds just fine. :-)

Jun-Young