Mark J. Wielaard

Just did an aptitude dist-upgrade to get planet.classpath.org and the main IcedTea backup server from Debian Etch to Debian Lenny. Pretty smooth.

Needed to adjust some apache2 NameVirtualHost settings as outlined in the release notes. And sadly, had to pin mercurial to 0.9.5, since newer versions don’t work nicely with the forest extension and serving hg through http with hgwebdir. But that was it. Everything else went without any hiccups.

But if you use one of those servers and do notice something wrong, please let me know.

Another nice feature for Systemtap 0.9 was added by Josh Stone. Systemtap can collect data from any variable in scope at a probe point using the DWARF debug info. You can even dereference pointers, access struct members, array elements, etc. This is very powerful when collecting data during a trace and the systemtap runtime makes sure all data access is safe. But there were two issues making this less powerful than it could be.

First to the keep the tracing language simple systemtap only supports basic types (integers and strings), associative arrays or aggregates in stap scripts. This means that you could not easily pass program data around to an helper function to manipulate or format. Second sometimes programs “hide” the real type of a variable, or use a void * pointer that gets cast to the right type later on. You could work around this in the past by using embedded C and guru mode, but that wasn’t very nice, and made your script potentially unsafe.

So to make sure you can do this safely Josh added a @cast construct. This allows you to pass around a pointer to program data and interpret it as if it was any type described in the DWARF debuginfo for the program. All accesses are of course still checked for safety by the runtime.

A nice example of this feature in action is the following simple stap script to print the number of incoming connections for an executable by port number. We want to probe the kernel and get the inet_sock from the inet_csk_accept function when it returns successfully. Although this function handles inet sockets (it is part of inet_connection_sock.c), it passes around sock pointers. It can do this since an inet_sock struct starts with a sock pointer, later it will cast this to a full featured inet_sock pointer. So we do the same in our script:

global ports;

probe kernel.function("inet_csk_accept").return
{
  sock = $return
  if (sock != 0)
    {
      port = @cast(sock, "inet_sock")->num;
      ports[execname(), port]++;
    }
}

probe timer.s(30), end
{
  printf("Connections on ports: %s\n", ctime(gettimeofday_s()));
  foreach ([exec, port] in ports-)
    printf("%12s %4d: %4d\n", exec, port, ports[exec, port]);
  delete ports;
}

$ stap ports.stp
Connections on ports: Sat Feb 28 22:49:10 2009
       httpd   80:  172
       spamd  783:   30
        exim   25:   27
     portmap  111:   11
  imap-login  993:    8
      ypserv  818:    7
        sshd   22:    2

There are some more exciting network tracing examples in the Systemtap Examples collection.

We recently released Systemtap 0.9 and one of the nice new features included is the user space markers that Stan Cox has been working on. They were designed so that they should be compatible with dtrace static user space markers, so you can immediately take advantage of them if your program already has those included. It even comes with a little dtrace python script wrapper that automagically does the right thing during the build. A nice example of that is postgresql, which has a set of markers to observe transactions, database locks, etc. All you have to do is recompile postgresql with –enable-dtrace and tada, out roll systemtap enabled markers that you can use for getting some high level events from your database. Like for example (postgresql-transactions.stp) how many and how long transactions take:

$ stap -x `pgrep -n postgres` postgresql-transactions.stp
committed transactions:
transaction id: time
            34: 1593213ns
            36: 2817146ns
            37: 1463901ns
            38: 1427854ns

aborted transactions: 4

We are trying to get some of these static markers activated in packages compiled for Fedora as SystemtapStaticProbes F11 Feature, so you can use them out of the box.

But you can also add your own markers to existing code. Daniel Tralamazza has been experimenting with a small glibc patch to add markers around various pthread mutexes, for doing userland synchronization primitives analysis. Then you can easily get things like the top 10 most shared locks.

Sarah has been publishing sets of pictures from the Fosdem Free Java Meeting.

IcedTea 1.4 got released this week. And while it is full of new exciting stuff, you really should check out the XRender support by Clemens Eisserer. Especially if you often use java through remote X. It just flies! Trying it out is easy as soon as the new IcedTea hits a distro near you:

java -Dsun.java2d.xrender=True my.fancy.gui.HelloWorld

Also check out the JGears2 benchmark to compare your results.

So this speeds up the rendering pipeline to X enormously. Now the next step will be optimizing or rewriting the actual Render backend (pisces at this time) which seems to be the next bottleneck, at least for anti-aliased operations.

Clemens will give a talk about his work at Fosdem. Hope to see you all there.

Sometimes people ask me what Red Hat actually pays me for. Aren’t you working on something java related? Although my manager has been very generous and allows me to spend some (but not too much!) time on helping out the free java efforts, my main job is in the engineering tools group (gcc, gdb/Archer [formerly Frysk], binutils, elfutils, oprofile, etc.). Currently I am hacking on Systemtap which has been a lot of (low-level) fun.

LWN just published my article “A Systemtap update” which gives a high level overview of the project through some small examples (all work out of the box on Fedora 10 of course).  It is tucked away on the LWN kernel page, but I tried to show how Systemtap moved beyond the kernel and now provides complete system observability. At the end of the article I point out some of the other work that is being doing around debugging and tracing (elfutils dwarf framework, gcc vta branch, froggy/archer, the user-space breakpoint support layer) to show it is all connected to provide a better debugging and tracing environment for GNU/Linux.

Looking for a handy reference of all the talks in the Free Java developer room at Fosdem 2009 in Brussels, Saturday 7 and Sunday 8 February? Look no further! PDF Poster and ODG Poster.

Our libre-java meeting at Fosdem is approaching quickly. February 7 and 8 in Brussels, Belgium. If you want to give a talk, do a demo or have some general presentation/hack-session in our room, please act quickly so we can still schedule it (the deadline is end of this week!).

This is what will be at our disposal:

• the room “AW1.120″ with a capacity of 74 seats (in the building “AW”)
  • on Saturday 2009-02-07 from 12:00 to 18:00
  • on Sunday 2009-02-08 from 09:00 to 17:00
• a video projector with VGA cable
• Internet connectivity (wifi A and B only, no wired)

This is what we need from you:

• Talk proposals and abstracts for activities.
  Please submit these BEFORE Saturday January 10!
  Either by emailing the Fosdem meeting committee at:
  fosdem2009@developer.classpath.org
  Or adding your proposal to the wiki:
  http://wiki.debian.org/Java/DevJam/2009/Fosdem

Also please add you name to the wiki even if you don’t want to present something so we know roughly how many people to expect.

planet.classpath.org moved servers and if done correctly nobody will notice (except for the new server having a totally sweet favicon ). But if you do happen to notice anything odd with the planet after the move, then please do yell and scream.

Without much fanfare systemtap 0.8 was released a little while ago. There is one little tidbit in the release notes that does warrent some excitement though:

User space probing is supported at a prototype level, for kernels built with the utrace patches.

So what does that mean? Take for example the para-callgraph.stp script:

$ stap para-callgraph.stp 'process("/bin/ls").function("*")' -c /bin/ls
0 ls(12631):->main argc=0x1 argv=0x7fff1ec3b038
276 ls(12631): ->human_options spec=0x0 opts=0x61a28c block_size=0x61a290
365 ls(12631): <-human_options return=0x0
496 ls(12631): ->clone_quoting_options o=0x0
657 ls(12631):  ->xmemdup p=0x61a600 s=0x28
815 ls(12631):   ->xmalloc n=0x28
908 ls(12631):   <-xmalloc return=0x1efe540
950 ls(12631):  <-xmemdup return=0x1efe540
990 ls(12631): <-clone_quoting_options return=0x1efe540
1030 ls(12631): ->get_quoting_style o=0x1efe540
[...]
650290 ls(12631):  <-print_current_files
650330 ls(12631): <-print_dir
650456 ls(12631): ->free_pending_ent p=0x1f02d90
650539 ls(12631): <-free_pending_ent
650660 ls(12631): ->close_stdout
650821 ls(12631):  ->close_stream stream=0x376db6c780
650966 ls(12631):  <-close_stream return=0x0
651082 ls(12631):  ->close_stream stream=0x376db6c860
651164 ls(12631):  <-close_stream return=0x0
651205 ls(12631): <-close_stdout

That is timestamp, process name, tid, function entry and function exit with parameters and return values. Currently it relies on having the debuginfo files available, so make sure you install the coreutils-debuginfo package (if you want to trace /bin/ls and friends). Systemtap 0.8 should be in a distro near you soon. Fedora 10 already has it.

Another nice thing added in Fedora 10 is oprofile-jit, which enhances the system profiler with java support (for runtimes supporting jvmti/jvmpi, gcj native code was obviously already supported), just add -agentlib:jvmti_oprofile to your java invocation, and then opreport can give you stuff like:

samples  %        linenr info                 image name   app name    symbol name
136220   20.3345  (no location information)   21010.jo     java        Interpreter
15176     2.2654  indexSet.cpp:528            libjvm.so    libjvm.so   IndexSetIterator::advance_and_next()
12273     1.8321  (no location information)   21010.jo     java        int[] java.math.BigInteger.montReduce(int[], int[], int, int)
11129     1.6613  (no location information)   21010.jo     java        int java.text.CollationElementIterator.next()
9932      1.4826  (no location information)   21010.jo     java        java.lang.String com.sun.javatest.finder.JavaCommentStream.readComment()~1
9731      1.4526  (no location information)   21010.jo     java        java.nio.charset.CoderResult sun.nio.cs.UTF_8$Decoder.decodeArrayLoop(java.nio.ByteBuffer, java.nio.CharBuffer)
9239      1.3792  reg_split.cpp:409           libjvm.so    libjvm.so   PhaseChaitin::Split(unsigned int)
8617      1.2863  ifg.cpp:464                 libjvm.so    libjvm.so   PhaseChaitin::build_ifg_physical(ResourceArea*)

Note how you can see the percentages of time spend in the interpreter, compiled methods, hotspot (and if I would have it enabled, libc, kernel, etc). The above is clearly a somewhat short run (of the jtreg crypto tests) and you can see that most of the time is spend in the Interpreter because the methods haven’t been compiled yet.

Paul wrote about “Fedora 10 around the corner!” and said something really nice:

Last, but certainly not least, I want to thank you, the reader, if I haven’t already. You’re part of our community too, and without you we would be diminished. Free software isn’t just about bits and bytes, it’s about people, about doing something real, something tangible, something lasting for your fellow human beings. And with your help, the Fedora Project has been able to lead in free software innovation for over five years and ten releases now. Each and every one of you — pat yourself on the back for a job well done.

Thanks Paul, very well said.

This post by Kirill Grouchnikov from Pushing Pixels made me sad:

Trust is hard to build and easy to destroy

Are we really doing that badly? Ever since the full GPL release by Sun of the reference implementation of Java as OpenJDK and the positive wave that IcedTea brought to unite the existing libre java communities pushing Java into the core of the various GNU/Linux distros, I feel like the sky is the limit. We as a community now have the full freedom to cooperate with each other in whatever way we like. But for some the feeling is still not there. Are we afraid to really define “Java the next generation”? It seems the code and the spirit is there. But there is a leadership trust issue. How do we fix that?

There is always a lot going on in the low levels of the GNU Toolchain (gcc, binutils, gdb, etc) but since it is so low level and sometimes a bit specialised it is hard to keep up. Luckily Nick Clifton started a blog writing a monthly GNU Toolchain Update. This month saw lots of GCC updates (a new register allocator, a new set of loop transformation optimizations, a new picoChip port and more). Really recommended for those who want to keep informed about the latest GNU Toolchain improvements.

We bought an Acer Aspire One A150 Ab, which comes with Linpus, a stripped down Fedora GNU/Linux distro. It also came with a nice printed GPL in the box explaining what it meant and various offers for the source code. The stripped down Fedora is somewhat limited, so we might upgrade it to a full Fedora install. What was cool to see was that it came with IcedTea and gcjwebplugin configured out of the box.

Free Java for your netbook!

Benjamin Mako Hill, who is now on the board of the FSF, has a really great site Revealing Errors that has as goal to reveal errors that reveal the technology around us to learn how technology affects our lives. Wish I had seen this site earlier. As he explains it is a great way to reach users and show how technologies affect our lives, and why Free Software is so important:

Errors are under-appreciated and under-utilised in their ability to reveal technology around us. By painting a picture of how certain technologies facilitate certain mistakes, one can better show how technology mediates. By revealing errors, scholars and activists can reveal previously invisible technologies and their effects more generally. Errors can reveal technology—and its power and can do so in ways that users of technologies confront daily and understand intimately.

He gave a really nice introduction to the whole concept in his Revealing Errors OSCON Keynote (ogg/theora).

Finally upgraded my main workstation from Fedora 8 to Fedora 9. If you are lazy like me then you might want to do it through Fedora PreUpgrade:

$ yum install preupgrade
$ preupgrade

Very nice and completely painless!

It also offers an easy way to go from Fedora 9 to Rawhide (the development branch).

From the “Freedom Fry” press release:

The GNU operating system is turning 25 this year, and the Free Software Foundation (FSF) has kicked off its month-long celebration of the anniversary by releasing “Happy Birthday to GNU,” a short film featuring the English humorist, actor, novelist and filmmaker Stephen Fry.

“Yum, chocolately good! The tastiest operating system in the world… and it’s all free!”

And don’t forget to start preparing for Software Freedom Day on September 20 and the GNU anniversary on September 27.

So what is the first thing you try out on your little bare arm board when you get IcedTea, Cacao and gcjwebplugin working? You try to play slime volleyball of course!

Read all about it on Xerxes Rånby’s blog.

Just saw A Lazy Developer Approach: Building a JVM with Third Party Software by Nicolas Geoffray, Gael Thomas, Charles Clement and Bertil Folliot. They show something I always found super cool about the community around GNU Classpath and the free software community in general. Working together on parts of free software to enable everybody to stand on top of the shoulders of giants.

The development of a complete Java Virtual Machine (JVM) implementation is a tedious process which involves knowledge in different areas: garbage collection, just in time compilation, interpretation, file parsing, data structures, etc. The result is that developing its own virtual machine requires a considerable amount of man/year. In this paper we show that one can implement a JVM with third party software and with performance comparable to industrial and top open-source JVMs. Our proof-of-concept implementation uses existing versions of a garbage collector, a just in time compiler, and the base library, and is robust enough to execute complex Java applications such as the OSGi Felix implementation and the Tomcat servlet container.

They have some nice things to say about GNU Classpath and our VM Interface

Industrial JVMs often have their own implementation of garbage collection, compilation, interpretation and class libraries. Open-source JVMs tend to all use the GNU Classpath base library implementation [6] (some JVMs are currently being ported to the newly open-sourced Sun implementation), and the Boehm garbage collector [22]. GNU Classpath and Boehm GC are popular among JVM implementations because they are virtual machine agnostic, hence they do not depend on a particular JVM implementation.

[...]

We started the project with GNU Classpath version 0.93. LadyVM now uses the latest version, 0.97.2. Since GNU Classpath has had many releases before 0.93, the API changes between 0.93 and 0.97.2 were minimal.

GNU Classpath moved to java version 1.5, including generics, with release 0.95. Since the JVM specification did not change between version 1.4 and 1.5, the move to GNU Classpath 0.95 did not require any changes in LadyVM. The only modification we made was due to the ldc opcode, which loads classes since JVM 1.5.

So next time you want java somewhere, just pick up the free software pieces already there and click them together for your environment :)

Things that make you smile:

From: Matthias Klose
To: debian-68k@lists.debian.org
Subject: building openjdk-6 for m68k

the openjdk-6 6b11-4 should build on m68k. It may take a few weeks, but I currently don’t see any issue with it. If you do so, please keep the build tree, so that the testsuite can be run, after the build finishes (taking some more weeks to finish).

It is a pure IcedTea Zero interpreter for Hotspot build (unfortunately the cacao m68k jit is currently “broken” :{ ), which explains the long, long, long build time. But if you have some spare m68k machine around and a couple of spare weeks, please do give it a try.

You would hope that Sun would get it by now, but apparently not :{

From the new JavaFX license:

“Licensee is not authorized to modify, make derivative works of, disclose, distribute, reverse engineer or disassemble the Technology, decompile binary portions of the Technology, or otherwise attempt to derive source code from such portions, or transfer the Technology to any third party or use it in development activities.”

“Licensee shall have no right to use the Technology for commercial uses or in a production environment.”

“Java Technology Restrictions. You may not create, modify, or change the behavior of, or authorize your licensees to create, modify, or change the behavior of, classes, interfaces, or subpackages that are in any way identified as “java”, “javax”, “javafx”, “sun” or similar convention as specified by Sun in any naming convention designation.”

Sigh.

Update It gets better:

“It is understood and agreed that, notwithstanding any other provision of this Agreement, Licensee’s breach of Sections 2.0 (Limited Licenses), 3.0 (Restrictions), 6.0 (Term and Termination), and/or 7.0 (Confidential Information) of this Agreement will cause Sun irreparable damage for which recovery of money damages would be inadequate…”

It is as if someone from Sun Legal was reading the Ubersoft episodes Grand Design and Ultimate Goal while drafting this license.

Andrew Haley and Thomas Fitzsimmons wrote a really nice article for Red Hat Magazine called Open source project: OpenJDK detailing our libre java journey from the perspective of Fedora and Red Hat. From Sun’s first announcement, GNU Classpath & GCJ, bootstrapping IcedTea, gcjwebplugin, webstart, PPC and the zero port, OpenJDK6, to being (almost) Java SE Compatible. Go read it!

When you upgrade to Fedora 9, make sure you get the zero-day update of icedtea/openjdk that Lillian made. It includes some sound fixes, Gervill midi support, the hat tool and fixes for javaws/netx. Then try out Jake2 (GPLed Quake engine in Java using Jogl and Joal). Just click that Jake2 webstart link, it will just work out of the box. Awesome!

German court tells Skype to obey the GPL:

“If a publisher wants to publish a book of an author that wants his book only to be published in a green envelope, then that might seem odd to you, but still you will have to do it as long as you want to publish the book and have no other agreement in place.”