jdk8 metasapce load class过多，问题查找相关命令

最新推荐文章于 2025-05-30 12:59:23 发布

czj1992czj

最新推荐文章于 2025-05-30 12:59:23 发布

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博客讲述了在JDK8中，由于使用protostuff导致Metaspace区域的类持续增加，进而引发Full GC，严重影响服务性能。通过`jstat -gcmetacapacity`和`jstat -gc`命令来监控Metaspace的状态，并提供了`-verbose:class`参数用于打印类加载信息，帮助定位问题。

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一次上线因为使用protostuff的序列化与反序列化导致Metaspace区域的class一直增长，从而导致metaspace区域full gc，以致服务很卡顿。
提供以下方法查看metaspace相关情况
jstat -gcmetacapacity 9536
MCMN       MCMX        MC       CCSMN      CCSMX       CCSC     YGC   FGC    FGCT     GCT
0.0 1060864.0    12800.0        0.0 1048576.0     1536.0    21     0    0.000    1.589

Metaspace size statistics.

MCMN: Minimum metaspace capacity (kB).

MCMX: Maximum metaspace capacity (kB).

MC: Metaspace capacity (kB).

CCSMN: Compressed class space minimum capacity (kB).

CCSMX: Compressed class space maximum capacity (kB).

YGC: Number of young generation GC events.

FGC: Number of full GC events.

FGCT: Full garbage collection time.

GCT: Total garbage collection time.

jstat -gc 9536
S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT     GCT
4096.0 512.0   0.0    64.0 57856.0 10360.7   212992.0    2873.2   12800.0 12366.4 1536.0 1398.9     21    1.589   0      0.000    1.58

S0C: Current survivor space 0 capacity (kB).

S1C: Current survivor space 1 capacity (kB).

S0U: Survivor space 0 utilization (kB).

S1U: Survivor space 1 utilization (kB).

EC: Current eden space capacity (kB).

EU: Eden space utilization (kB).

OC: Current old space capacity (kB).

OU: Old space utilization (kB).

MC: Metaspace capacity (kB).

MU: Metacspace utilization (kB).

CCSC: Compressed class space capacity (kB).

CCSU: Compressed class space used (kB).

YGC: Number of young generation garbage collection events.

YGCT: Young generation garbage collection time.

FGC: Number of full GC events.

FGCT: Full garbage collection time.

GCT: Total garbage collection time.

打印load class jvm 参数:-verbose:class