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Hi in a web service with openjdk 21.0.3 using G1GC with heap size 26GB, we recently sometimes observed a huge jump up of the oldgen like from 9GB to 20GB in about 3 minutes and then slowly returned to 9GB (which is the normal size) in about 30 minutes, checking
jmap histo we found:</div>
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num #instances #bytes class name (module)</div>
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1: 6328181 16406573984 [Ljdk.internal.vm.FillerElement; (java.base@21.0.3)</div>
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2: 18920559 1233399640 [Ljava.lang.Object; (java.base@21.0.3)</div>
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3: 18813814 848534768 [B (java.base@21.0.3)</div>
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4: 5939383 771222984 [I (java.base@21.0.3)</div>
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5: 3093810 654462640 [J (java.base@21.0.3)</div>
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6: 15519103 496611296 java.util.HashMap$Node (java.base@21.0.3)</div>
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7: 17985808 431659392 java.util.Date (java.base@21.0.3)</div>
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8: 17415598 417974352 java.util.ArrayList (java.base@21.0.3)</div>
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9: 16857329 404575896 java.lang.String (java.base@21.0.3)</div>
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10: 9743073 389722920 java.math.BigDecimal (java.base@21.0.3)</div>
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11: 4410896 281417160 [Ljava.util.HashMap$Node; (java.base@21.0.3)</div>
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Any idea for why the class jdk.internal.vm.FillerElement has so large size? There seems to be less document for this class. Thanks in advanced!</div>
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The jdk vendor we using is </div>
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openjdk version "21.0.3" 2024-04-16 LTS</div>
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OpenJDK Runtime Environment Temurin-21.0.3+9 (build 21.0.3+9-LTS)</div>
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OpenJDK 64-Bit Server VM Temurin-21.0.3+9 (build 21.0.3+9-LTS, mixed mode, sharing)</div>
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And the gc otpionwe using is</div>
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-Xms26g -Xmx26g -Xss300k -XX:+UseG1GC -XX:MaxGCPauseMillis=200 -XX:ParallelGCThreads=16 -XX:ConcGCThreads=8 -XX:InitiatingHeapOccupancyPercent=30</div>
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