On Sun, 15 Apr 2012 17:43:22 +0300
Konstantin Belousov kostik...@gmail.com wrote:
On Sun, Mar 11, 2012 at 10:59:00AM +0100, John Marino wrote:
Hi Konstantin,
It seems that no BSD supported DT_GNU_HASH despite this option
being available on the base binutils (FreeBSD's 2.17.50 binutils
supports it). This gnu extension is a big performance improvement
over the specified SysV hash.
The guy porting libreoffice to pkgsrc was finding
-Wl,--hash-style=gnu to be the default build for that package.
Indeed, using the standard hash results in very long startup times
for something like Writer ( 8 seconds launched from a SSD)
The result is that we brought in DT_GNU_HASH support to our
real-time linker this weekend. We're still waiting to see how that
improves libreoffice startup times.
full commit:
http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/7629c6317998f850ebca23c296822ba08af09e5b
Modification to base compiler so all system libs and binaries can
take advantage of it:
http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/4687ecd9561d76f3d02ccb4f7adeecd5e3afdd8f
For a while, binaries with dynamic symbol tables will have both
types of hashes embedded. At some point in the future, we may
switch over to only generating the GNU hash. This will break
forward compatibility, but that happens rather frequently for other
reasons anyway.
I was a bit surprised FreeBSD didn't already have this
functionality given the performance benefits, so hopefully these
DragonFly commits will be interesting for you.
I finally ported the Dragonfly commit to FreeBSD. There were several
changes reverted in dragonfly version of the extracted
matched_symbol() function which were restored. I also blindly
converted all non-x86 arches.
The matched_symbol() extraction is the good opportunity to apply the
style(9) formatting to the large chunk of rtld code.
Any testers, esp. on non-x86 architectures, are welcome. You would
need to modify gcc spec file for you architecture, see corresponding
x86 changes in contrib/gcc/config/i386.
For me, patch successfully worked on the machine were I disabled sysv
hashes at all.
http://people.freebsd.org/~kib/misc/rtld-gnu_hash.1.patch
Nothing jumps out, looks good. I am not a fan of mixing and matching
different styles within the same file though.
--
Alexander Kabaev
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