I hope I'm not the only one who sometimes wonders: "What is my Java application doing right now?" When you don't see any output. This is where my tiny tool called JStall comes in, as you can read in my blog post at mostlynerdless.de/blog/2025/12...

youtu.be/nyOR3H9txP4 No google emails, hashgraph, smart contracts, GC, Ethereum. Foreign langs and programming. Build systems, deterministic build, concurrent builds, mail providers.

Mount Mayhem at Netflix: Scaling Containers on Modern CPUs

In this week's blog post, you'll learn that JFR doesn't like arrays in other complex types as fields in custom JFR events, and what types are supported: mostlynerdless.de/blog/2025/12...

I just implemented a tool accepting a .pdb file to generate a .sym file listing functions symbols. A first post (chnasarre.medium.com/9826fd4f251e...) shows the coding details. I'm sharing my vibe coding experience using Cursor in a second longer one (chnasarre.medium.com/f957106a3e9f...)

My latest blog: One Positive Effect of Java 25 with Compact Object Headers Enabled donraab.medium.com/one-positive...

I'm happy to announce that my meta-agent (a Java agent that instruments other Java agents) now has a nicer Web UI (thanks @hardcoding.fr): github.com/parttimenerd...

C2: create better fill and copy benchmarks, taking alignment into account bugs.openjdk.org/browse/JDK-8... github.com/openjdk/jdk/... …interesting and informative discussions Via @forked-franz.bsky.social on twitter x.com/forked_franz...

TIL: Early exit makes 'javac' to duplicate 'finally' blocks. Interesting read: www.benf.org/other/cfr/fi...

Help--my LocalDate isn’t flattened! Just before my Valhalla talk at JFall, I found out that the early access build can flatten LocalDate arrays, but the latest version from Github cannot. Why? Serialization, of course. Read the gory details at https://horstmann.com/un...

youtu.be/Z3OJ0K5fReA C++ Compile times. Ethereum byte code and runtime. Java and exceptions; more C++ compile times. Fat binaries & code portability. Language design around memory safety

Latency Profiling and Optimization

✏️ JEP 8371379 was drafted Title: Deprecate the UTF-16-only Internal String Representation Type: feature Component: core / lang See openjdk.org/jeps/8371379

🎯 JEP 526 proposed to target JDK 26 Title: Lazy Constants (Second Preview) Type: feature Component: core / lang Release: 26 See openjdk.org/jeps/526

🎯 JEP 500 proposed to target JDK 26 Title: Prepare to Make Final Mean Final Type: feature Component: core Release: 26 See openjdk.org/jeps/500

🎯 JEP 516 proposed to target JDK null Title: Ahead-of-Time Object Caching with Any GC Type: feature Component: hotspot / gc See openjdk.org/jeps/516

Learn how to import JFR data into DuckDB, to easily query and analyze your profiling data in this week's blog post: mostlynerdless.de/blog/2025/10...

I just published a new article: Using profiler function hooks in .NET with Silhouette. In the process, we also learn how to use static linking with NativeAOT. minidump.net/using-functi...

Method tracing in async-profiler 4.2 github.com/async-profil... Also there’s system-wide process sampling on linux, this ends up in a `profiler.ProcessSample` JFR event. (I would love to see something like that on Darwin too). github.com/async-profil... #async-profiler

@pminborg.bsky.social and I wrote a bit about some of the many performance improvements in JDK 25: inside.java/2025/10/20/j... tl;dr: upgrade to JDK 25 and add -XX:+UseCompactObjectHeaders

A nice article about "Memory Allocation in Go" #golang nghiant3223.github.io/2025/06/03/...

Can We Know Whether a Profiler is Accurate? Spoiler: yes we can! But it took us figuring out a way to work around the fundamental observer effect. stefan-marr.de/2025/10/can-... If you're at SPLASH, don't miss our talk at VMIL today and at OOPSLA on Saturday!

This looks like something to follow. There's some investing numbers. engineering.fb.com/2025/10/06/d... #zstd #openzl

JDK Memory corruption on AArch64 Byte code Rewriting, this can lead to impossible branch being taken among other issues. (via Ismael Juma on Twitter) bugs.openjdk.org/browse/JDK-8... #openjdk

youtu.be/wYO4-s8WsnA Modules, std lib, abi, portable ELF, cffi, build systems, dependencies, project root, xtc modules, as directories, diff in “module” impls, meaning of “import”, foreign modules. Typechecking dead code? Combinatorial explosion build targets

Ever seen a verbose render how a very small GC operation looks like in the context of larger safepoint? Here it is: (I need to blog about things you can see there)

Learn how to compare objects from JFR recordings in Java and why this is slightly trickier than you might have expected in this week's blog post: mostlynerdless.de/blog/2025/10...

Wow, just noticed that Netty 5 will have the Java 25 baseline ! github.com/netty/netty/... #netty #java #java25

OMG it makes a huge difference. Without even pinning to tier 1 ("dev" mode) we have a new record base startup of 361ms on my M4 MBA. I'm playing with some other tweaks and a longer training run now.

New post: JRuby and JDK 25: Startup Time with AOTCache Let's take a look at JRuby's startup time journey, all the way up to using JDK 25's AOTCache and Project Leyden features coming to a JDK near you soon. blog.headius.com/2025/09/jrub...

Today I learned that since #JDK 11, there is now in thread dumps - cpu=... : the time the thread spent executing on the CPU. - elapsed=... : the wall clock time passed since the thread was started. bugs.openjdk.org/browse/JDK-8... I’m not proud to have missed that 🤦‍♂️

Nice engineering blog post on some query filtering at scale. There are some lessons in there. They used a "bloofi " multidimensional bloom filters. axiom.co/blog/buildin... lemire.me/en/publicati...

New toy, "residence graphs": tracking the compilation level for top method in the stack. On the left, normal JIT mode: compilers are busy, intp -> T2 -> T3 code is hot; T4 code slowly takes over. On the right, normal AOT+JIT (Leyden) mode: AOT code carries most of it, JIT happens to plug the holes.

"Method Tracing" in async-profiler: github.com/async-profil...

SIMD Within a Register: How I Doubled Hash Table Lookup Performance Learned about SWAR the first time in the one-billion row challenge. Nice explanation including benchmarks.

youtu.be/q4mRNu6_lpc C++ debugging, -Og, safepoints, adr sanitization. kefir (from scratch C compile), SCCP in Simple, graph DSL. Strict aliasing, implicit conversions. Pointer comparison. GPU Kernels DSLs (Triton, Gluon, TLX), Object layout, NUMA. Distributed random forest

Nice usage of #zstd for tarball via Kelly Sommers on Twitter. x.com/vmg/status/1...

📝 Blogged: "Let's Take a Look at... Lower Java Tail Latencies With ZGC" As #Java 25 got released earlier this week, I took the ZGC garbage collector for a spin, exploring how it lives up to its promise of sub-millisecond GC pause times. 👉 www.morling.dev/blog/lower-j...

With Java 25, there is finally a CPU-time profiler in the OpenJDK. You can read more about this new profiler and some implementation details in my blog series starting with mostlynerdless.de/blog/2025/06... #java25

What Makes System Calls Expensive: A Linux Internals Deep Dive. blog.codingconfessions.com/p/what-makes... Another great post by @abhi9u.bsky.social. I learned a lot, including vDSO.

JChateau our Unconference organized in France in the area of the Châteaux of the Loire Valley is open for registration at : www.jchateau.org/registration...

Java 25 / JDK 25: General Availability: mail.openjdk.org/pipermail/jd... Features: openjdk.org/projects/jdk... Downloads: jdk.java.net/25/ #Java25 #JDK25 #OpenJDK #Java

Oracle detaches #GraalVM from the Java SE train 👀 • JDK 24 = last with Graal JIT / GraalVM in Java SE • Native Image discontinued for #Java SE (-> Leyden) • GraalVM team pivots to non-Java (GraalPy, GraalJS) 👉 Java devs: migrate to C2 JIT & track Leyden AOT work blogs.oracle.com/java/post/de...

youtu.be/5YIhnjThoK4 Burning Man, boats diving between dust devils. LSP, C backend, debug info, codegen , zydis, ASM. Ryan/quxlang update - literal types, bitwise operators, keywords, functions, containers. LLVM LogicalResult. GCC and LLVM funding, Triton, Cuda, ML , Mojo

Let's Take a Look at... JEP 483: Ahead-of-Time Class Loading & Linking! buff.ly/vXDtFq9 #Java #jdk #jep483

The date have been confirm to 04-08 march 2026, registration will open soon

🎓 JEP 523 moved to candidate Title: Make G1 the Default Garbage Collector in All Environments Type: feature Component: hotspot / gc See openjdk.org/jeps/523

The xCapture and xtop eBPF tools are now in beta, with a demo dataset! With a pre-recorded xcapture dataset from my dev server, now you can play with xtop "thread activity sampling" drilldown even on your laptop, without having to run xcapture yourself! (link in replies :-)

#java JEP 401 on value classes is submitted : openjdk.org/jeps/401

youtu.be/qhfhluIory0 C++/11,20,26; partial -g code; Java vs C++ speed with debugging. x86/arm vs java mem model. x86 intrinsics in Java. LSPs. C++ vs Java containers. Compile-time alloc size. UI frameworks. Teaching programming via games. C++ default copy/move opers