Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel) profile picture

Sr Sw Eng @Datadoghq, optimize software running on JVM. Love performance topics and mechanical sympathy supporter. Java Champion & @javamissionctrl committer

Paris
Joined September 2010
Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)Photo by Jean-Philippe Bempel @jpbempel.bsky.social (@jpbempel)
Jean-Philippe Bempel @jpbempel.bsky.social retweeted
youtu.be/KYmSz_oqJO0 Simple update, interprocedural SCCP; next steps. No libc; language agnostic interfaces, Windows metadata. JNI and handles, Closure, stack layout, C interop, CLR, OS, hardware flavors. LLVM compat. AI & Security policies, quorums. Core update
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
Corretto 8, 11, 17, 21, 25, and 27 have all been released with the latest security improvements, including the removal of eMudhra root certificates. (Third time is the charm. Go hug your friendly JDK vendor!)
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
youtu.be/aO93VU8QZbA Simple update, Chapter split, constructors, helper functions. Codex, tokens, costs. AI success stories, optimizing Python gc, PyPy. Making a VM, hardware mismatch, memory segments, mapping pages in VM memory, self modifying code , patching JIT targets
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
arstechnica.com/security/202… The private keys for these certs are literally the numbers 4, 56, 66, 115, 155, 156, 230, and 237 (life imitates XKCD, again).
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
youtu.be/nWjTshirDhI - AI the good bad ugly. Tarjan SCC with AI. Price of memory, chip fabs, HBM. Steam OS for work. Simple Update, cyclic class init, Goose. Core update, ARM, RISC V backends. Pattern matching, tracking deps, C2 philosophy , global vars. AI, nnarrow tasks
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
Datadog released Scout 1.0, its first model built to investigate production incidents. Scout is built on GLM-5.3 Flash. Datadog post-trained it with reinforcement learning in simulated investigations made from real historical incidents and telemetry. Datadog scores it on AlertEval, its own internal benchmark annotated by human experts. Scores measure agreement with expert reference explanations on a 0 to 100 scale. At medium effort, Scout matches GPT-6.1 Sol high and Claude Opus 5.5 high at 3 to 8 times lower estimated inference cost. At xhigh effort it matches Claude Fable 5.1 xhigh at 4 times lower cost. On the third-party SREGym benchmark, Scout medium beats GLM-5.3 at more than 4 times lower cost. Scout is in a closed preview, and Datadog runs the AlertEval numbers itself. My read: Datadog says Scout medium performs comparably to Fable medium at 12 times lower cost, and to Astra medium at 19 times lower. Divide 19 by 12 and you get about 1.6. So on this benchmark Astra medium has about 1.6 times the estimated cost of Fable medium for a comparable score. datadoghq.com/blog/ai/introd…
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
JEP 544 (openjdk.org/jeps/544), the remaining part of Leyden has landed in JDK mainline. So now we can do this! This source launcher involves javac compilation, that is the bulk of the work here.
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
GPT + Opus (via Copilot CLI) helped me uncover 180 JIT bugs, each with a minimal C# repro using only safe code 😶 - most had been hiding from us for many releases github.com/dotnet/runtime/is…
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
youtu.be/yuU_usRj3JY Talk at REBASE. Peeps during parsing - less memory, faster compile. Inst sel, reg alloc, encodings. Lattice types, GCM. Anti-deps. JIT, deterministic builds & exec. Pointer orderin Simon update (non kernel platform apis). cyclic class defs
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
Java—The Year of the Runtime! As AI accelerates coding, the JVM matters more than ever: compatibility, integrity, JIT compilation, performance, memory management, and JFR telemetry. AI Enterprise software will remain secure, robust, efficient on the JVM. youtu.be/fXBGBovpH88?si=3ZoG…
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
youtu.be/yU4oGuM2xf8 Simon on CORE unions/enums, and modules. Slow compiler, due to over-inlining on co-routine frames (52Meg stack frames???). Halo - heap alloc opt elision (static inline allocs on stack frames).
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
Reminder: JDK fastdebug binaries exist and useful for low-level testing. If you suspect a JVM bug, those builds could assert more meaningfully. downloads.corretto.aws has lots of them. So does builds.shipilev.net/. There Docker images too, ex: shipilev/openjdk:25-fastdebug.
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
I published a new article: the hidden trap of fixed buffers in C#. It explains a quirk of fixed buffers that could easily bite you, if you're one of the few people who still have to use that feature. minidump.net/the-hidden-trap…
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
Did you know you can call JNI without writing native code, patch bytecode without an agent, and use Unsafe without warnings? 11 sneaky ways into JDK internals through reflection, agents, FFM, type confusion, bytecode manipulation and more. wouter.coekaerts.be/2026/dec…
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Jean-Philippe Bempel @jpbempel.bsky.social retweeted
youtu.be/7U6im0HQXt8 Simple demo, Visual Compiler, visual optimizations. Forward refs, Escape node, Readonly in the type, inline, noinline, modules, linking with libc, calling foreign function. .o internals. Security flaws in java. Audit for nuclear power plant
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