g1gc | 易学教程

Is there a GC in Java that does not introduce latency (stop-the-world) by perhaps running 100% concurrently?

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问题 Just curious. I heard something about the new G1GC addressing that latency problem. I can't / don't want to use RTSJ. Thanks in advance 回答1: I don't think there are any zero-pause garbage collectors. But generally speaking a low-pause collector like CMS will do the job. The problems with pauses and pause reduction are as follows: A zero-pause (or almost zero-pause) collection regime significantly increases overheads for normal program execution. This is particularly true with multithreaded

Spark: shuffle operation leading to long GC pause

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问题 I'm running Spark 2 and am trying to shuffle around 5 terabytes of json. I'm running into very long garbage collection pauses during shuffling of a Dataset : val operations = spark.read.json(inPath).as[MyClass] operations.repartition(partitions, operations("id")).write.parquet("s3a://foo") Are there any obvious configuration tweaks to deal with this issue? My configuration is as follows: spark.driver.maxResultSize 6G spark.driver.memory 10G spark.executor.extraJavaOptions -XX:+UseG1GC -XX

Tuning G1GC params for aggressive garbage collection?

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My JVM is basically a spark executor which is running tasks one after another. A task is memory hungry and requires significant memory during its lifecycle. JConsole and JVisualVM report side by side The above JVM is running on G1GC with default params. As you can see in the VisualVM report on the right hand side between 4:25 to 4:32 PM, the spikes are due to each tasks run by the executor (essentially, each spike is due to the executor picking up new task after the previous one is finished). When I triggered a manual GC at 4:35, I saw a sharp decline the heap usage. Also, as you can see on

Experience with JDK 1.6.x G1 (“Garbage First”)

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问题 I'd like to know what are the experiences with G1 garbage collector in newest JDK? I see NullPointerException thrown in my program, although code didn't change and behave correctly in earlier JDKs. 回答1: I've been running jEdit using: -Xmx192M -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC for the last couple of days on windows. Haven't experienced anything going wrong or misbehaving. I also tried running Intellij using the G1 GC, it didn't fair so well. It lasted a couple of hours before

G1GC long pause with initial-mark

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With j7u5, G1GC "-Xms3200m -Xmx3200m -XX:+UseG1GC -XX:ParallelGCThreads=14 -XX:ConcGCThreads=4 -XX:MaxGCPauseMillis=40 -XX:NewRatio=2 -XX:SurvivorRatio=10 -XX:+PrintGC -XX:+PrintGCDateStamps" for a given performance test, my application hits a long pause after 5-hour run predictably. Except this big one (and only), there are small initial-mark phases. Any suggestions to figure out what is happening to this long pause and how to tune it to avoid such a long pause which affects the latency targets (percentiles 98%, 99.999%)? 2012-12-22T09:48:57.966+0000: [GC pause (young) 2436M->1460M(3200M), 0

Why does G1GC shrink the young generation before starting mixed collections?

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问题 When G1 decides it needs to start doing mixed collections, it aggressively shrinks our Eden space from 10g to about 1g. {Heap before GC invocations=294 (full 0): garbage-first heap total 20480000K, used 18304860K [0x00000002de000000, 0x00000002de804e20, 0x00000007c0000000) region size 8192K, 1363 young (11165696K), 11 survivors (90112K) Metaspace used 37327K, capacity 37826K, committed 38096K, reserved 1083392K class space used 3935K, capacity 4081K, committed 4096K, reserved 1048576K 2016-03

Is there a GC in Java that does not introduce latency (stop-the-world) by perhaps running 100% concurrently?

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Just curious. I heard something about the new G1GC addressing that latency problem. I can't / don't want to use RTSJ. Thanks in advance I don't think there are any zero-pause garbage collectors. But generally speaking a low-pause collector like CMS will do the job. The problems with pauses and pause reduction are as follows: A zero-pause (or almost zero-pause) collection regime significantly increases overheads for normal program execution. This is particularly true with multithreaded languages like Java. Schemes that use a dedicated thread or threads to do garbage collection can get swamped

G1GC remark phase is taking too long

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问题 My server application under load some times goes unresponsive and i found the issue to be related to very long "GC Remark". There is no garbage collection tuning implemented. My test server is a 4 core/8 gb/8 GB swap. This is the log output from gc logs. 2014-04-06T04:39:58.426+0530: 67263.405: [GC remark, 46.7308340 secs] 2014-04-06T04:40:45.167+0530: 67310.146: [GC cleanup 1951M->1750M(2954M), 0.0037930 secs] 2014-04-06T04:40:45.174+0530: 67310.153: [GC concurrent-cleanup-start] 2014-04

Why does G1GC shrink the young generation before starting mixed collections?

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When G1 decides it needs to start doing mixed collections, it aggressively shrinks our Eden space from 10g to about 1g. {Heap before GC invocations=294 (full 0): garbage-first heap total 20480000K, used 18304860K [0x00000002de000000, 0x00000002de804e20, 0x00000007c0000000) region size 8192K, 1363 young (11165696K), 11 survivors (90112K) Metaspace used 37327K, capacity 37826K, committed 38096K, reserved 1083392K class space used 3935K, capacity 4081K, committed 4096K, reserved 1048576K 2016-03-31T20:57:31.002+0000: 7196.427: [GC pause (G1 Evacuation Pause) (young) Desired survivor size

Latencies issues which G1GC

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I am facing a continues increase in GC pauses with G1GC algorithm. The service latencies continue to grow over time. Once this happens, i restart my service and the latencies go back to normal. Post startup, the latencies again continue to increase over time. At the time of startup, the service latencies are around ~200ms, but within 24 hours, they go up to 350ms, and continue to increase in a linear fashion. The increase in service latencies match the increase in GarbageCollection metrics. Service specifications I am running a java application (JDK-8) on M4-2X Large EC2 boxes with 50 active