JieTan created FLINK-36394:
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Summary: Configure Init Metaspace size by default
Key: FLINK-36394
URL: https://issues.apache.org/jira/browse/FLINK-36394
Project: Flink
Issue Type: Bug
Components: API / Core
Affects Versions: 1.17.2, 1.16.0
Reporter: JieTan
Attachments: image.png
We should set the size of the Init JVM Metaspace to a sane default, like
{{{}-XX:MetaspaceSize=128m{}}}.
When a Flink job starts, it needs to load class metadata information, including
class structure information, method information, and field information. As a
result, the JVM frequently performs FullGC. Sometimes, the Metadata GC
Threshold (Full GC) is 3.7s long before the Akka System is started.
``` bash
2024-07-23T20:08:40.554+0800: 1.801: [Full GC (Metadata GC Threshold)
2024-07-23T20:08:40.554+0800: 1.801: [Tenured: 0K->14029K(966656K), 0.0336205
secs] 108273K->14029K(1401664K), [Metaspace: 20594K->20594K(1067008K)],
0.0337494 secs] [Times: user=0.02 sys=0.00, real=0.04 secs]
2024-07-23T20:08:42.052+0800: 3.300: [Full GC (Metadata GC Threshold)
2024-07-23T20:08:42.052+0800: 3.300: [Tenured: 14029K->28979K(966656K),
0.0503497 secs] 184494K->28979K(1401664K), [Metaspace:
34384K->34384K(1079296K)], 0.0505108 secs] [Times: user=0.04 sys=0.00,
real=0.05 secs]
2024-07-23T20:08:45.064+0800: 6.312: [Full GC (Metadata GC Threshold)
2024-07-23T20:08:45.064+0800: 6.312: [Tenured: 28979K->54550K(966656K),
0.0876744 secs] 248437K->54550K(1401664K), [Metaspace:
57015K->57015K(1099776K)], 0.0879053 secs] [Times: user=0.07 sys=0.01,
real=0.09 secs]
```
The final Metaspace size takes up 100MB+.
*Solution:*
{*}I{*}f we configure Init Metaspace size by default. As a result, Flink job
Metaspace FullGC reduced.
``` bash
OpenJDK 64-Bit Server VM (25.362-b09) for linux-amd64 JRE
(1.8.0_362-ByteOpenJDK-b09), built on Feb 20 2023 09:42:31 by "root" with gcc
8.3.0
Memory: 4k page, physical 4018480k(137636k free), swap 0k(0k free)
CommandLine flags: -XX:CompressedClassSpaceSize=260046848
-XX:GCLogFileSize=104857600 -XX:InitialHeapSize=3368026112
-XX:MaxHeapSize=3368026112 -XX:MaxMetaspaceSize=268435456
-XX:MetaspaceSize=134217728 -XX:NumberOfGCLogFiles=5 -XX:+PrintGC
-XX:+PrintGCDateStamps -XX:+PrintGCDetails -XX:+PrintGCTimeStamps
-XX:+UseCompressedClassPointers -XX:+UseCompressedOops
-XX:+UseGCLogFileRotation
```
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