Workshops at SPLASH 2010

As usual I will write about a few of my personal highlights of SPLASH and the co-located workshops. That is mostly from my spotty notes, and from memory, so I don’t guarantee 100% accuracy, especially with respect to what other people might have said.

For an impression on the location itself, I will just cite and refer to what Nick wrote on the JOT blog:
“Reno airport was like a gateway into hell, slot machines everywhere […] The conference venue is almost comically grim. The main floor is a sea of slot machines and haggard looking people.”
So, it was definitely not the most exciting place ever, and I was already worried that my colleagues start to shoot at those zombies 😉

Anyway, from the content point of view, it was actually a nice conference for me.

On Sunday the Virtual Machine Intermediate Languages workshop took place. As last year, that is the most relevant workshop with respect to VMs I came across so far. This year, especially the invited talks were very interesting.

A JVM Does What????

Cliff Click started with reporting on his perception of JVMs and the illusions they provide to the developers. My take away from his talk are the following points.

First, garbage collection is still the major issue, and people are willing to pay for better performance here. He kind of implied that JIT compilers are nice to have, but not as high on the list of priorities for his typical customers.

Second, he wants people to explore alternative concurrency models on top of the VM. From his perspective, the JVM is a great platform and things like locks are cheap. He agrees that things like Erlang-like Actors need deeper hocks into the Java Memory Model and possibly the JIT compiler, but in general I understood that he would rather prefer something on top instead of another thing integrated into the VM. Well, lets see how my ideas work out.

Related to my ideas we had a small discussion afterwards with David. I was surprised that Azul uses a Uniform Memory Access model for its systems but apparently the problem is that current business applications exhibit random access patterns all over the heap. Thus, if you have a system with 16 chips and 16 memory controller, 15/16 of the access are going remote anyway. That is why the optimize for that case instead of optimizing local performance. Interesting, but perhaps just the consequence of not having appropriate languages which take locality into account in the first place.

SPUR: A Trace-Based JIT Compiler for CIL

Nikolai Tillmann reported on the SPUR project at Microsoft Research. He gave a introduction to tracing-based just-in-time compilation and also present some benchmarks. The interesting part about SPUR is that they actually JIT .NET but experiment mainly with JavaScript.

For me the most interesting aspect of his talk was the future work section were he mentioned a few attempts on parallelizing code by the tracing JIT. Their ideas mainly focus on vectorization which is kind of not so exciting, hope they will also look into speculative execution, even so Nikolai asks for more hardware support for such an idea.

A Systematic Mapping Study on High-level Language Virtual Machines

The first research paper I am going to mention here was meta research on VM research.

The authors surveyed the body of literature on VMs to find out what people are doing research on. Well, the scope was a bit to narrow to actually cover all interesting papers, but it is a very nice first step. David was a bit disappointed that his Self and other Smalltalk papers were not covered and that the literature that was identified as being relevant only started in the 90’ies or so. Well, the authors were already aware of those limitations, but beside this definitely constructive criticism, the audience also came up with proposals to get us as the community involved. There is serious interest in such research and people would be happy with helping classifying (and certainly promoting their own research) if that could happen on a wiki or so…

The Architecture of DecentVM – Towards a Decentralized Virtual Machine for Many-Core Computing


The second research paper with high relevance for myself was about DecentVM. The DecentVM is based on the distributed DecentSTM. It implements a JVM currently running on a distributed system. However, they also want to look into how to make it run on Intel’s Single-chip Cloud Computer. So, some interesting work coming up there.

How’s the Parallel Computing Revolution Going? Towards Parallel Scalable Virtual Machine Services

Kathryn McKinley reported on experiments her students did to compare the speed and power consumption of CPUs over the last few years. Turns out, the power consumption seems to rise faster than the performance, especially since the benchmarks do not scale perfectly for multicore applications. However, there is quite a bit of progress with respect to saving energy instead of increasing performance with Intel’s Atom and related architectures.

Interesting was her proposal to parallelize the VM in itself. Something Theo always asks for, too. However, Cliff Click basically said that HotSpot is already at that point for most parts. So, at least from his perspective, that is not a field where major breakthroughs will come from…

Monday, the second day of workshops was less interesting. I started in the day with giving my presentation at the Doctoral Symposium. Did not get more than meta-feedback, unfortunately. I guess, it was just to early for that. What I have is an idea (perhaps with to many open design options) and a plan to validate it. But it was obviously still too fluffy… On the other hand, that meant I was missing great workshops like for instance Evaluate 2010 and the Dynamic Languages Symposium *sigh*

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