g1gc

问题 I have hit counter running on Java. It works 24 hours and hits pass at about 100 times per second. During the day GC processing time slowly rises from 20-60 ms till 10000-60000 ms and then drops to 20-60 ms. Such pattern is repeated from time to time. From GC logs I found that mostly all time GC spend for processing Reference objects (Ref Proc). So what's the causes of such long GC time could be? Server: Amazon EC2 m1.small OS: Ubuntu 10.04.3 LTS Java: Oracle 1.7.0_07 Example of GC logs: 2012

问题 I'm currently evaluating the G1 garbage collector and how it performs for our application. Looking at the gc-log, I noticed a lot of collections have very long "Scan RS" phases: 7968.869: [GC pause (mixed), 10.27831700 secs] [Parallel Time: 10080.8 ms] (...) [Scan RS (ms): 4030.4 4034.1 4032.0 4032.0 Avg: 4032.1, Min: 4030.4, Max: 4034.1, Diff: 3.7] [Object Copy (ms): 6038.5 6033.3 6036.7 6037.1 Avg: 6036.4, Min: 6033.3, Max: 6038.5, Diff: 5.2] (...) [Eden: 19680M(19680M)->0B(20512M)

问题 JEP 192: String Deduplication in G1 implemented in Java 8 Update 20 added the new String deduplication feature: Reduce the Java heap live-data set by enhancing the G1 garbage collector so that duplicate instances of String are automatically and continuously deduplicated. The JEP page mentions that a command-line option UseStringDeduplication (bool) allows the dedup feature to be enabled or disabled. But the JEP page does not go so far as to indicate the default. ➠ Is the dedup feature ON or

问题 Java 7 has been out for a while now, but I cannot find any good resources on the configuration of the garbage collectors , specifically the new G1 collector . My questions: Is G1 the default collector in Java 7 and if not how do I activate G1? What optional settings does g1 have in Java7? Were there any changes made to other collectors like cms or the parallel collector in Java 7? Where can I find good documentation on garbage collection in Java 7? 回答1: The G1 garbage collector is not the

问题 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).

问题 I am trying to test running with string interning to see if it helps ease the massive memory requirements of intellij. In order to use java 8's built in interning you need to run the G1GC. However adding this parameter to the user idea.vmoptions file causes the jvm to fail to start. It is definitely this parameter only and other collectors seem not to be an issue. The bundled jre is 8u40 and i'm running on OS X. 12/28/16 11:06:24.559 AM idea[15003]: JNI_CreateJavaVM (/Applications/IntelliJ

问题 A seemingly straightforward question: why does G1 GC spend so much time in the 'termination' phase? A non-full GC takes ~2 seconds, and from that, 1.5 sec is the termination (work stealing) phase. Context: - our app has apprx. 10MB/sec allocation rate - most of those are short-lived objects - termination time is increasing linearly with app uptime - we have a large heap (24G) - full GC never occurs, if I force it manually then GC times are back to normal - the app itself does a lot of

问题 We have been testing out G1 garbage collector recently with the following configuration: -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+UseG1GC -XX:MaxGCPauseMillis=1250 -XX:+PrintTenuringDistribution -Xloggc:${logdir}/gc-$(date +%Y_%m_%d-%H_%M).log -XX:+UseStringDeduplication -XX:+PrintStringDeduplicationStatistics -XX:+PrintPromotionFailure -XX:+PrintAdaptiveSizePolicy -XX:+PrintHeapAtGC -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=100M -XX:

问题 For a week after switching to java 1.7.0_80, observed this behavior S0C S1C S0U S1U EC EU OC OU PC PU YGC YGCT FGC FGCT GCT 0 32M 0 32M 512M 128M 9.5G 7.7G 640M 475M 26487 157min 0 0min 157min No Full GC, large space allocated to old generation and too many collections happening in young generation. After invoking full GC via JMX S0C S1C S0U S1U EC EU OC OU PC PU YGC YGCT FGC FGCT GCT 0 32M 0 32M 5.2G 768M 4.8G 2.7G 640M 475M 26592 158.4min 1 0.1min 158min And GC times reduced a lot.

问题 I set ParallelGCThreads=1 and use G1 GC , all other JVM settings are default. I run PageRank on Spark-1.5.1 with two EC2 nodes 100 GB heap each. My heap usage graph is below (Red area: young generation, black area: old generation). All young GCs are small, all of a sudden there comes one young GC that collects 60 GB, then young GCs become small again. My GC logs shows no mixed GCs, no full GCs, one concurrent marking, and tens of young GCs. I am wondering why that huge young GC happens? A