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Reposted by Stefan Marr

Stefan Marr @stefan-marr.de · 27/09/2026

Brief weekend reading on another benchmarking pitfall: The Limitations of Running a Workload Generator In the Same JVM as the System-Under-Test norlinder.nu/posts/The-Li... Spoiler: the GC may conspire against you and your data collection!

norlinder.nu

The Limitations of Running a Workload Generator In the Same JVM as the System-Under-Test

If you care about tail latency in SPECjbb2015, Composite mode hides GC impact. We quantify the discrepancy and recommend Distributed or MultiJVM.

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Stefan Marr @stefan-marr.de · 27/09/2026

norlinder.nu

The Limitations of Running a Workload Generator In the Same JVM as the System-Under-Test

If you care about tail latency in SPECjbb2015, Composite mode hides GC impact. We quantify the discrepancy and recommend Distributed or MultiJVM.

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Stefan Marr @stefan-marr.de · 23/09/2026

They tell me to stay on top of this technology. Alright, but... "my research subagent went beyond its assigned scope, edited the file and made git commits itself, despite being instructed to only research and report."... it's broken by design. Why'd you give it the capability?

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Reposted by Stefan Marr

Laurence Tratt @ltratt.bsky.social · 21/09/2026

It was amusing to read that the current "AI makes lectures irrelevant" debate has echos from 1781 as related by Boswell.

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Stefan Marr @stefan-marr.de · 19/09/2026

I thought, I had broken the iteration-time foldout of ReBenchDB. Turns out, it was just terribly slow. Scanning through a 2GB data table on a slow disk takes a while. Fix the primary key order, i.e., the relevant index, and instead of waiting 42sec, it shows in 34ms.

Screenshot of ReBenchDB's iteration time foldout, showing detailed data for the benchmark in addition to the short-form summary.

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Reposted by Stefan Marr

Laurence Tratt @ltratt.bsky.social · 28/08/2026

For those wondering, yk is chugging away: support is broadening and in the last couple of days I've merged things which speed up interpreters by at least 5% (some by quite a bit more). There is a lot more juice to be squeezed, of course, but every little helps!

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Stefan Marr @stefan-marr.de · 28/08/2026

VMIL'26 has a program! Looks very interesting. Static Analysis, optimizing Android's GC, understanding R's benchmarks, optimizing Ruby, and lots more! The SPLASH early registration deadline is September 3rd! Program: conf.researchr.org/home/splash-...

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Reposted by Stefan Marr

Stefan Marr @stefan-marr.de · 20/08/2026

Benchmarking is hard, and there are many pitfalls out there. Let's look at some fictitious examples and think of what could have caused the behavior we are seeing: stefan-marr.de/2026/08/pitf...

stefan-marr.de

Pitfalls of Benchmarking on Modern Systems

Modern hard- and software systems have a lot of features, which make programs fast, but can make it difficult to understand what is going on. Let's look at some fictitious benchmark results a think th...

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Reposted by Stefan Marr

Laurence Tratt @ltratt.bsky.social · 06/08/2026

The video of my QCon talk from this March is now up www.infoq.com/presentation...

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Reposted by Stefan Marr

Stefan Marr @stefan-marr.de · 22/07/2026

Are you working on language implementations and implementation research? Do you want to present your work to an enthusiastic crowed in Oakland? Submit your work to the VMIL Workshop! conf.researchr.org/home/splash-...

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Stefan Marr @stefan-marr.de · 22/07/2026

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Stefan Marr @stefan-marr.de · 08/07/2026

How come, we academics are so terrible at "knowledge transfer"? We can't even make sure that this year's organizers of an event know everything they need to know, and the organizers last year already had to learn. I guess, it's not a priority. 😩

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Stefan Marr @stefan-marr.de · 30/06/2026

Christoph shows how to reduce the size of @graalvm.org native images. We can get pretty far with fairly basic heuristics. Basic, means cheap during compilation. 2026.ecoop.org/details/mplr...

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Stefan Marr @stefan-marr.de · 30/06/2026

Thomas presenting his work on unifying GCs to be able to have different GCs with different tradeoffs in the same AOT compiled binary. 2026.ecoop.org/details/mplr...

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Stefan Marr @stefan-marr.de · 29/06/2026

We know where it's going to fail. Good luck and safe travels!

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Stefan Marr @stefan-marr.de · 29/06/2026

Markus is using pedagogic comments in execution traces to enable students to look at debugging sessions with guiding comments. Learning how to program in the very first year, based on debuggers and visualization. 2026.ecoop.org/details/debt...

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Stefan Marr @stefan-marr.de · 29/06/2026

Can we use meta-compilation to ahead-of-time compile dynamic language programs from an interpreter? Maybe! Christoph talked about the approach he will try out. 2026.ecoop.org/details/ICOO...

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Stefan Marr @stefan-marr.de · 25/06/2026

Arrived an hour later than planned, but had to start an hour earlier...

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Stefan Marr @stefan-marr.de · 25/06/2026

Now on an earlier ÖBB Train (instead of DB), might make this journey possible.

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Stefan Marr @stefan-marr.de · 25/06/2026

First train is cancelled

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Stefan Marr @stefan-marr.de · 24/06/2026

Traveling across central Europe by train tomorrow. Theoretically, a 11h journey with two changes. What are the odds that I will arrive on time? 1. Very good 2. 50:50 3. Deutsche Bahn? 🤣

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Reposted by Stefan Marr

Stefan Marr @stefan-marr.de · 16/06/2026

Lots of us from the SSW will be attending @ecoop-conference.bsky.social, come and talk to use at ICOOOLPS, MPLR, the Demo Track, DEBT, ECOOP Academy, and at the poster session! Christoph A. is presenting early ideas of how to make AOT meta-compilation work for dynamic languages. 1/...

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Stefan Marr @stefan-marr.de · 16/06/2026

... reduce the size of AOT-compiled Java programs. Melissa presents a visual debugger designed for teaching threads and locks in Java. And last but not least, I'll give a lecture on benchmarking. All details here: stefan-marr.de/2026/06/ssw-...

stefan-marr.de

SSW@ECOOP'26: On GC, Debugging, Benchmarking and (Meta-)Compilation

Come and talk to us at ICOOOLPS, MPLR, the Demo Track, DEBT, ECOOP Academy, and at the ECOOP poster session!

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Stefan Marr @stefan-marr.de · 16/06/2026

Markus is presents work on enriching educational debuggers with explanations and interactive questions. Thomas presents a fairly simple approach to support different GCs within the same AOT-compiled binary. Christoph P. will show that simple heuristics can allow us to 2/...

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Stefan Marr @stefan-marr.de · 16/06/2026

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Stefan Marr @stefan-marr.de · 12/06/2026

Re SC: I suspect sigplan.org/Conferences/... is also very outdated. Looks like the last update is3 years ago :( github.com/SIGPLAN/SIGP...

sigplan.org

Onward!

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Stefan Marr @stefan-marr.de · 12/06/2026

Re stop reading policy: I'd expect that this would just extends the "agentic loop" (copy in reviewer comments and resubmit) and keep the flood of low quality submissions in the system, going just to the next victim. If there are no consequences, I doubt we will be able to uphold our values for long

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Stefan Marr @stefan-marr.de · 12/06/2026

For Onward!, for which you are listed as SC member, I reviewed obvious slop. If we don't do something about it, it will break all the good things we are trying to achieve with venue like Onward!. I wish we could bar authors that abuse the system from submitting for a while.

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Reposted by Stefan Marr

Carlos Baquero @xmal.bsky.social · 09/06/2026

Pleased to announce that the application deadline for the Fourth ACM Europe Summer School on Distributed and Replicated Environments (DARE 2026) has been extended to 19 June 2026! This extension is made possible thanks to additional funding from ACM and SIGSOFT. dare-milan.github.io

dare-milan.github.io

DARE 2026

Fourth ACM Europe Summer School on <br> Distributed and Replicated Environments (DARE 2026)

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Stefan Marr @stefan-marr.de · 09/06/2026

The writers however made him have at least two encounters with women: Tasha Yar and Jenna D’Sora. But especially the second one could be interpreted as Data not being truly into women.

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Stefan Marr @stefan-marr.de · 27/05/2026

Might have won something. Instead of 10h with @deutschebahn.com, they want me to travel 20h with them... Enjoying 10 trains and busses, instead of 3... Got rebooked "automatically" it seems. Thanks AI!

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Reposted by Stefan Marr

Erik Österlund @eosterlund.bsky.social · 22/05/2026

Today, May 22, my book about ZGC is finally ready and available to order! I can recommend reading it if you want to learn more about the magic nature of ZGC. You can order it here (among many places): www.routledge.com/The-Z-Garbag...

routledge.com

The Z Garbage Collector: In JDK 25

This book explains how the Z Garbage Collector was designed, why it was designed this way, the common pitfalls to avoid when using ZGC in JDK 25 and how to get useful information from the garbage coll...

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Stefan Marr @stefan-marr.de · 21/05/2026

Looking forward to reading it!

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Reposted by Stefan Marr

Ben Hermann @benhermann.eu · 18/05/2026

REMINDER: Our call for a professorship in the programming language field ends this Sunday! Make sure your application is in the system on time.

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Stefan Marr @stefan-marr.de · 16/05/2026

Are you offering? I finally have access to excellent students 😀

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Stefan Marr @stefan-marr.de · 15/05/2026

It's all running on a vServer online somewhere and I am too stingy to pay more...

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Stefan Marr @stefan-marr.de · 15/05/2026

I think, I'll be carefully exploring 32bit. This thing is already slow and uses too much storage...

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Stefan Marr @stefan-marr.de · 15/05/2026

Ugh. Past me underestimated how many experiments future me is going to run. ReBenchDB just overflowed 16bit ints on the number of trials (i.e., experiments per benchmark machine). Is this something to celebrate? The number of collected measurements already requires 24bits...

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Reposted by Stefan Marr

Stefan Marr @stefan-marr.de · 14/05/2026

The program of ICOOOLPS is now online: 2026.ecoop.org/home/ICOOOLP... And today is the last day for early registrations. Interested in programming language implementation, compilation, and optimization? Join us in Brussels! Don't know what to expect? 1/2

2026.ecoop.org

ICOOOLPS 2026 - ECOOP 2026

The ICOOOLPS workshop series brings together researchers and practitioners working in the field of language implementation and optimization. The goal of the workshop is to discuss emerging problems an...

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Stefan Marr @stefan-marr.de · 14/05/2026

... Here the MoreVMs recordings from earlier this year, and yes, in-person, the sound was perfect 🙈: www.youtube.com/playlist?lis... 2/2

youtube.com

MoreVMs 2026 - YouTube

Recordings of the MoreVMs workshop in Munich, March 2026

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Stefan Marr @stefan-marr.de · 14/05/2026

2026.ecoop.org

ICOOOLPS 2026 - ECOOP 2026

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Reposted by Stefan Marr

ECOOP '26 @ecoop-conference.bsky.social · 07/05/2026

⏳ 7 days left for early registration at #ECOOP2026! Don't miss your chance to hear Sandrine Blazy take us from mechanized semantics to verified compilation, and find out what 15 years of Viper looks like through Peter Müller's eyes. 📍 Brussels, BE | Jun 29–Jul 3 2026.ecoop.org/attending/re...

2026.ecoop.org

Registration - ECOOP 2026

ℹ️ Early registration deadline: May 14th! Click here for all registration information

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Reposted by Stefan Marr

Stefan Marr @stefan-marr.de · 06/05/2026

Towards Least-Privilege WebAssembly Applications: Transparent Interposition for WebAssembly Components Olav Blaak talked about his approach to fine-grained security policies for Wasm components. youtu.be/a3a_le54tW0 This one was another MoreVMs'26 talk.

youtu.be

Towards Least-Privilege Wasm Applications: Transparent Interposition for WebAssembly Components

YouTube video by programmingconf

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Stefan Marr @stefan-marr.de · 06/05/2026

youtu.be

Towards Least-Privilege Wasm Applications: Transparent Interposition for WebAssembly Components

YouTube video by programmingconf

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Stefan Marr @stefan-marr.de · 05/05/2026

No! But it has slides, audio, and video. Something that eluded me since I started here... Sigh. Software...

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Stefan Marr @stefan-marr.de · 05/05/2026

Lecture 7, and we have a recording. Some said it would be impossible. Others suggested that computers were a mistake in the first place. And sometimes I reminded myself of younger me who observed/predicted that professors have no technical skills any longer. Is it perfect? 1/2

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Stefan Marr @stefan-marr.de · 04/05/2026

At this point, the expectations from the students to get recordings is zero. Maybe it's a good thing. But, I won't be defeated by technology! Wish me luck 🙈

$ffmpeg8 \ -probesize 50M -analyzeduration 50M -f avfoundation -capture_cursor 1 -framerate 30 -pixel_format uyvy422 -i "${SCREEN_IDX}:none" \ -probesize 50M -analyzeduration 50M -f avfoundation -framerate 30 -video_size 1920x1080 -pixel_format nv12 -i "${CAMERA_IDX}:${MIC_IDX}" \ -map 0:v -c:v h264_videotoolbox \ -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black" \ -pix_fmt yuv420p -color_range pc -b:v 5M -movflags frag_keyframe+empty_moov \ "${NAME_PREFIX}_screen.mp4" \ -map 1:v -map 1:a -c:v h264_videotoolbox \ -pix_fmt yuv420p -color_range pc -b:v 2M -c:a aac_at -b:a 192k -movflags frag_keyframe+empty_moov \ "${NAME_PREFIX}_webcam_mic.mp4"$

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