Featured · Runtime
What the JIT Actually Does to Your Hot Loop
Tiered compilation, on-stack replacement and inlining decide how your loop really runs. Here is how to read those decisions instead of guessing.
Marcus Venn
Java, runtimes, frameworks, and the systems beneath them.
Deep technical writing about the JVM and its ecosystem.
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Runtime
Streams Versus Loops: What the JIT Sees
The same pipeline cost 7.05 times the loop over eight elements and 1.31 times over a million. The ratio everyone quotes is a measurement at a trip count.
Runtime
The Cost of Optional
Identical source, five call sites, one JDK 26 run - nothing allocated at the first and twelve bytes at three others. The wrapper is not what decides.
Diagnostics
JFR: The Events You Actually Need
Sixty seconds of default settings produced 4.3 MB, three quarters of it one event type, and none of it answered whether the application was lock-contended.
Runtime
What a Safepoint Actually Stops
One collection, reported as 2.275 ms by the GC log and 29.6 ms by the safepoint log. The gap is time to safepoint, and each instrument hides a different part of it.
Runtime
How the JVM Finds and Loads a Class
A hello-world program loads 423 classes before it prints anything. Where they come from, what the JVM does to each one, and how to see it.
Frameworks
Where Spring Boot Startup Time Goes
Startup time is class loading, condition evaluation and JIT warmup in some proportion. Measure the split before reaching for a fix.