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libtool -prefer-non-pic for apxs builds?

php.internals

Rasmus Lerdorf

23 years ago

Guys, what do you think about defaulting the build to use -prefer-non-pic
and having libtool build a non-pic libphp4.so when building the Apache
DSO?  That library isn't linked into other programs anyway, and Apache's
fork+exec model ensures the pages will be shared regardless of pic.  I
don't really see what we gain by building it pic, and we certainly lose
quite a bit by doing so.  In the order of 15-20% execution time on both
FreeBSD and Linux with gcc in my tests.

-Rasmus

Ilia A.

23 years ago

On August 1, 2003 12:22 pm, Rasmus Lerdorf wrote:

> Guys, what do you think about defaulting the build to use -prefer-non-pic
> and having libtool build a non-pic libphp4.so when building the Apache
> DSO?  That library isn't linked into other programs anyway, and Apache's
> fork+exec model ensures the pages will be shared regardless of pic.  I
> don't really see what we gain by building it pic, and we certainly lose
> quite a bit by doing so.  In the order of 15-20% execution time on both
> FreeBSD and Linux with gcc in my tests.

I think this is a good idea, I've been manually doing the same thing on my
servers by compiling cli & apache separately. Performance wise in my
experience no-pic code is 25-30% faster on Linux. So far it worked perfectly
and I had not experienced any problems. I see no reason why we cannot offer
all PHP users the same performance advantages.

Ilia

Sascha Schumann

23 years ago

Not all dls support non-PIC code in DSOs.  If you know that
your system handles it fine, just pass the right -pic flag to
configure.

- Sascha

On Fri, 1 Aug 2003, Ilia Alshanetsky wrote:

Ilia A.

23 years ago

On August 1, 2003 04:03 pm, Sascha Schumann wrote:

>     Not all dls support non-PIC code in DSOs.  If you know that
>     your system handles it fine, just pass the right -pic flag to
>     configure.

Could we not add the appropriate checks to enable this setting for people's
who's dl support this? This is a fairly obscure point that most people are
not aware of and consequently suffer a significant and unnecessary
performance loss.

Ilia

Rasmus Lerdorf

23 years ago

On Fri, 1 Aug 2003, Sascha Schumann wrote:

>     Not all dls support non-PIC code in DSOs.  If you know that
>     your system handles it fine, just pass the right -pic flag to
>     configure.

Can't we check for that at configure time?

And I don't think we can do it at configure time currently.  At least the
obvious --without-pic doesn't work.  configure.in has:

unset with_pic

case $php_build_target in
program|static)
standard_libtool_flag='-prefer-non-pic -static'
if test -z "$PHP_MODULES"; then
enable_shared=no
fi
;;
shared)
enable_static=no
standard_libtool_flag=-prefer-pic
EXTRA_LDFLAGS="$EXTRA_LDFLAGS -avoid-version -module"
;;
esac

So it looks to me like the build target overrides the pic setting and
there is no way to build a shared library using -prefer-non-pic

-Rasmus