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Volker Simonis

Volker Simonis received a diploma and PhD degree in computer science from the University of Tubingen/Germany. After working for SUN Microsystems he switched to SAP where he's currently working in the JIT Compiler Technology group. You can check out his (somewhat outdated) website for more info.

 

simonis's blog

YAOJOWBI - Yet another OpenJDK on Windows Build Instruction

Posted by simonis on October 28, 2011 at 11:00 AM PDT

This blog describes how to build both, a 64-bit and a 32-bit version of OpenJDK 8 on a plain, vanilla WindowsXP 64-bit operating system using only free (as in free beer) tools.

Compiling the HotSpot VM with Clang

Posted by simonis on February 10, 2011 at 9:22 AM PST

At the FOSEDM 2011 I've heared Chris Lattner's very nice "LLVM and Clang" keynote. The claims he made in his talk have been very impressing: he was speaking about Clang being a "production quality" "drop-in replacement" for GCC with superior code generation and improved compile speed. Already during the talk I decided that I would be interesting to prove his pretensions on the HotSpot VM which in generally is not known as the worlds most simple C++ project. Following you can find my experiences with Clang and a small Clang patch f

"We need a 'dirty hack' (but a brilliant one)..."

Posted by simonis on February 20, 2009 at 9:37 AM PST

Usually it's not big fun to be "supporter of the week" but recently, when I was on duty, I got this somehow unusual request on our support queue. If you're interested in Bytecode Instrumentation and Rewriting, Classloaders and Instrumentation Agents read on to hear the full story...

HotSpot development on Linux with NetBeans - Part 2

Posted by simonis on January 24, 2008 at 4:33 PM PST

Here comes the second part of "HotSpot development on Linux with NetBeans". While the first part focused on building and running the different flavors (opt/debug, client/server JIT compiler, template/C++ interpreter) of the HotSpot VM on Linux/x86, this second part concludes with a short evaluation of NetBeans 6.0 as an development environment for HotSpot hacking.

HotSpot development on Linux with NetBeans - Part 1

Posted by simonis on January 24, 2008 at 4:31 PM PST

Here comes yet another step-by-step tutorial which explains how to fetch the OpenJDK sources, compile them and work with them inside the NetBeans IDE. It focuses on building and running the different flavors (opt/debug, client/server JIT compiler, template/C++ interpreter) of the HotSpot VM on Linux/x86 and concludes with a short evaluation of NetBeans 6.0 as an development environment for HotSpot hacking.

Template- vs. C++-Interpreter shootout

Posted by simonis on November 16, 2007 at 3:22 AM PST

The default interpreter that comes with the Hotspot VM is the so called "Template Interpreter". It is called template interpreter, because it is basically created at runtime (every time the Hotspot starts) from a kind of assembler templates which are translated into real machine code. In the earlier Java days (around JDK 1.4) a second interpreter existed beside the template interpreter - the so called C++ Interpreter. It was probably named that way, because the main interpreter loop was implemented as a huge switch statement in C++. Read in this article how the two interpreters compare to each other in terms of functionality and performance.

Testus Interruptus or how to avoid InterruptedExceptions in JCK tests

Posted by simonis on November 13, 2007 at 12:12 PM PST

Although JCK tests are not a regression test suite it is probably not uncommon that they (or at least a significant subset of them) are used as automated tests. To do this successfully, a number of JCK tests like for example interactive tests or tests which require a special setup have to be excluded from the test suite. This can be easily achieved with the help of exclude lists. Read in this blog how I discovered a bug in JTHarness which could led to spurious failures of arbitrary tests.

Top-secret "-Xintelligent_as_can_be_execution" option revealed!

Posted by simonis on August 30, 2007 at 9:19 AM PDT

Recently I did some benchmarking with the HotSpot and because my program was obviously too slow, I began to browse the HotSpot sources for some secret tuning parameters that could save my day. And indeed, after some digging, I found a real big fish: the "-Xintelligent_as_can_be_execution" option.