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
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