Reading GC logs
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
enable unified GC logging and read its key fields.
Planned topics
- Enable:
-Xlog:gc*:file=gc.log:time,uptime(verify flags for your JDK). - Each line shows the collection type, heap before -> after (total), and pause duration.
- Healthy: frequent short young pauses; heap after full/mixed collections returns to a stable floor.
- Warning signs: floor rising over time (leak), full GCs, pauses over the goal, back-to-back collections (allocation pressure).
- Tools such as GCViewer or GCeasy help; learn to read the raw lines first.
Draft outline details
Demonstration
[12.3s] GC(41) Pause Young (Normal) (G1 Evacuation Pause) 612M->140M(1024M) 8.4msCheck your understanding
What does 612M->140M(1024M) mean?
Show answer
Heap used before and after the pause, with current heap capacity.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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