alanc @ sun.com

Alan Coopersmith’s blog

Random thoughts of a disorganized mind...
(and though it should be obvious, while Sun pays me to think about things, they disclaim any responsibility for these thoughts, nor do I claim what I say matches in any way what Sun thinks)

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http://blogs.sun.com/alanc/date/20050711 Monday July 11, 2005

Can GNOME startup time be improved via ld flags?

Bryan Cantrill, Master DTrace Guru, First Class, spent some time today looking at what exactly GNOME is doing when you login to a Java Desktop System session on Solaris, and posted his findings to his weblog. (The current JDS on Solaris is based on GNOME 2.6, since that's what was the stable release last year when Solaris 10 hit feature freeze. The JDS team is working on an update to GNOME 2.10 now.)

One of the things Bryan found was that a large part of the I/O time was spent loading shared object text. I took a quick look at some of the binaries and libraries using elfdump, and noticed that there were no signs of using flags that could reduce the time needed to load shared libraries at process startup. Some of these (like -z lazyload) defer work until later - others (like -z combreloc) reduce the work needed whenever it happens.

I sent some suggestions to the JDS team on using these flags and others to improve this and suggested especially reading the Performance Considerations chapter of the Solaris Libraries and Linkers Guide for more ideas. I also cc'ed the linker gurus, and Senior Linker Alien Rod Evans added a suggestion to try out the check_rtime perl script on the binaries to check for the recommended flags and whether any of the libraries linked against aren't really needed. It's currently set up for use in the build system of the OS/Networking consolidation (the portion of the Solaris sources already released via OpenSolaris), but should be adaptable to the JDS build system or in fact, any project that wants to try to optimize it's library/linker use on Solaris.

Unfortunately, just tweaking the flags will mostly help Solaris, but the GNU binutils ld used on Linux and some other platforms offers some similar functionality - it recognizes many of the same -z options for instance, though I haven't tried them to see how they compare.

Something that may help more on both platforms is ensuring the libraries listed in the various .pc files for GNOME only list the direct requirements, not all the dependencies they depend on as well. For instance, look at what is linked into every program on Solaris that uses the gtk toolkit: 

alanc@unknown:~ [2] pkg-config --libs gtk+-2.0
-lgtk-x11-2.0 -lgdk-x11-2.0 -latk-1.0 -lgdk_pixbuf-2.0 -lm -lmlib -lpangoxft-1.0 
-lpangox-1.0 -lpango-1.0 -lgobject-2.0 -lgmodule-2.0 -lglib-2.0
But if you run elfdump -d /usr/lib/libgtk-x11-2.0.so you'll see libgtk-x11-2.0.so already lists those dependencies, so duplicating them in the applications simply wastes time as the linker at runtime will load libgtk-x11-2.0.so and have to check the same list of libraries it already checked in the application (though it should find it's already taken care of them and doesn't duplicate all the work). Additionally it hardcodes in the applications knowledge of the internals and backends used that they shouldn't need to know about, and makes it harder to change or replace one of them. While all those libraries need to be listed when statically linking, or on older systems (mainly pre-ELF I think), the pkg-config entries should be streamlined when using ELF shared libraries on modern systems.

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[Now Playing: Deep Space 9 series finale (recorded today off Spike TV by our TiVo)]

Posted at 11:01PM Jul 11, 2005 by Alan Coopersmith in Solaris  |  Comments[2]

Cylons using Sun Ray technology?

Craig asked a bunch of questions yesterday as he was trying to catch up on the new Battlestar Galactica. I posted a comment with some answers, but I realized this evening while making dinner that I missed a point that would really appeal to Craig - the Cylons are, like Sun Rays, ultra-thin clients. If the hardware is damaged beyond repair, the memories and consciousness (as much as a cybernetic being can be said to have one) is instantly transferred to a replacement hardware client. You don't even need to plug in a smartcard to the new Cylon body - it's automatic session migration.

Of course the problem with this is, it puts Sun on the wrong side of this galactic battle - for in the universe of the modern BSG, the network isn't just the computer, it's the very fabric of the Cylon civilization. Our ragtag team of survivors trying to escape genocide at the hands of the Cylons, however, is led by a ship designed to be completely non-networked, with all systems as isolated as possible to reduce the damage that can be done by a network attack. Oh well, you can't win them all (though the highly networked Cylons seem to be winning a lot of them so far).

(So who is going to make a back-and-forth red LED display add-on for the Sun Ray 170 so we can all have our own personal Cylons? It could even be functional - make the speed vary with the amount of bandwidth being used by the Sun Ray or the packet loss rate for remote deployments.)

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Posted at 09:54PM Jul 11, 2005 by Alan Coopersmith in General  |  Comments[3]