How to check memory leaks in java

Memory Leak Scenario

Memory leaks are likely to occur when a long-lived object holds a reference to a short-lived object. Although the short-lived object is no longer needed, because Holding its reference for a long life cycle prevents it from being recycled. This is the scenario where memory leaks occur in Java.

1. Check the CPU and memory usage during the process:

    top –H –p 58527

2. Check the server memory.

    df -h 查看磁盘情况
    du -h --max-depth=1 文件目录占用资源情况。

3. Check the memory, cache area, usage and idleness.

free -m

S0C: The capacity (bytes) of the first survivor (survivor area) in the young generation

S1C: The second survivor in the young generation (bytes) The capacity of the survivor area (bytes)

S0U: The first survivor (survivor area) in the young generation currently uses space (bytes)

S1U: The second survivor in the young generation The survivor (survival area) currently uses space (bytes)

EC: The capacity of Eden (Eden) in the young generation (bytes)

EU: The current capacity of Eden (Eden) in the young generation Used space (bytes)

OC: Old generation capacity (bytes)

OU: Old generation currently used space (bytes)

PC: Perm (Persistent Generation) capacity (bytes)

PU: Perm (persistent generation) currently used space (bytes)

YGC: gc in the young generation from application startup to sampling Times

YGCT: Time (s) used for gc in the young generation from application startup to sampling time

FGC: Number of gcs from application startup to old generation (full gc) during sampling

FGCT: The time (s) used for gc from the application startup to the old generation (full gc) during sampling

GCT: The total time (s) used for gc from application startup to sampling time

4. View the execution program information.

    jstack 2829 > 1.log    
 
    grep -A 1'java.lang.Thread.State' jstack.log | wc -l

5. Download the heap file analysis code Dump.

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