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Questions tagged [g1gc]

G1 or Garbage First is a generational partially collecting concurrent and parallel garbage collection algorithm. It is targeted for multi-processor machines with large memories and can meet soft realtime requirements with garbage collection (GC) pause time goals. An implementation of the G1 currently ships with the new Java 7 VMS - officially supported from JDK7 update 4.

G1 or "Garbage First" is a generational partially collecting concurrent and parallel garbage collection algorithm. It is targeted for multi-processor machines with large memories and can meet soft realtime requirements with garbage collection (GC) pause time goals.

An implementation of the G1 currently ships with the Java Hotspot 7 VM - officially supported from JDK7 update 4.

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Times in G1GC logs

I've read a few descriptions of different times printed in G1GC logs but couldn't really prove/understand when I produced them locally. For example, following log was produced on my PC with Java 11. I wanted to know, what's the difference between…
Abidi
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Why have different descriptions of heap usage in G1GC logs

I get 2 description for heap usage: occupancy: 21458059264 bytes and Heap: 15.5G(20.0G)->15.5G(20.0G). First log caused a full gc，but that conflicts with the second log，I'm confused. JDK is OpenJDK_1.8.0 2020-01-02T00:32:06.965+0800: 222101.010:…
a.fan
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Can we use G1GC Garbage Collector for smaller heap size

We need help regarding G1GC Algorithm , can we use this GC for low heap size around 1GB or this is only for bigger heap. We want to use this GC because we are getting "GC overhead limit exceeds" and application using the default GC collector.
Mohd shaban
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Why result of MemoryPoolMXBean.MemoryUsage.getUsed for old generation decrease without mixed GC under G1?

I can sure no mixed GC or full GC happened through GC log, but value of G1 Old Gen from MemoryUsage.getUsed decreased. From the following picture we can find that the old generation usage repeat grow very slowly and then decrease to a low value(It…
ganle hu
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why heap space is smaller than sum of young and survivors after young gc?

My jvm options: -verbose:gc -Xmx200M -Xmn40M -XX:+PrintTenuringDistribution -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+UseG1GC -XX:NewSize=40m -XX:MaxTenuringThreshold=1 -XX:-UseAdaptiveSizePolicy The following is gc log: Desired survivor size…
ganle hu
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Full GC in G1 GC

Jstat tool gives stats regarding young gc time and full gc time along with other information. As far as I know, Full GC in G1 GC consists of following phases : 1) Concurrent Marking (not Stop the world) 2) Remarking (Stop the world) 3) Reclaimation…
Rahul Patel
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Which reference Finalizer (FinalReference) or Weak/Phantom/Soft Reference have higher priority for GC

When object with non-trivial finalize() method is created, JVM will create Finalizer (FinalReference) with this object as referent. What will happen if this object will be also wrapped by Soft/Weak or Phantom Reference? Would GC try to enqueue the…
Martin
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How to calculate object promotion rate from g1gc logs?

I am using the below equation to calculate bytes promoted from parallel GC logs promoted_bytes = (('younggen_used_before_gc') - ('younggen_used_after_gc')) - (('heap_used_before_gc') - ('heap_used_after_gc')) How to calculate the same from G1GC…
Sreekanth Sharma
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What is Reference Processing in garbage collection process

I'm reading about G1 GC, and there are processes called "Reference Processing" and "Reference Enq" in both Young collection and Concurrent Marking cycle steps. What exactly are those processes? What will happen there?
Martin
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young GC pause vs STW pause

When young generation GC pause - Does it stop the application for any amount of time? Does the application have access to memory during this time? IIUC in stop the world GC (STW GC) application will be paused and won't have access to memory but…
Sagar
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G1 young gc suddenly took more time to complete

PFB logs. Young gc which took place at 2019-01-29T22:26:37.545+0000: took only 0.03 seconds. Where as young gc at 2019-01-29T22:27:04.257+0000 just after 30 sec or so took 1.87 seconds. Amount of memory collected is almost same in two gcs. I am…
user3087500
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Is JDK 6u14 Garbage First (G1) garbage collector, suitable for JRun?

Garbage First (G1) garbage collector http://weblogs.java.net/blog/opinali/archive/2009/02/here_comes_jdk.html Do you think this garbage collector is better for JRun, running ColdFusion 8?
Henry
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Why mixed GC could not clear memory while Full DC did?

Running G1GC (Java 8) with below MaxGCPauseMillis=100 InitiatingHeapOccupancyPercent=30 G1MixedGCLiveThresholdPercent=85 and memory is 115 GB. I notice that there was a Full GC and it brought down memory from 111GB to 65 GB. Prior to Full GC there…
user3660575
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G1GC support on elasticsearch 5.4.3

I am running 5.4.3 version of elasticsearch and currently facing issues with poor performance of CMS. I would like to know if G1GC is supported on 5.4.3 version of elastic-search and if there is any precaution to take while using G1GC.
sumit jha
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G1 gc suspicious long pauses

I have strange G1 gc pauses - gc spends a lot of time if 'Ref Proc' phase. I'm running hbase region server with following gc options Java HotSpot(TM) 64-Bit Server VM (25.192-b12) for linux-amd64 JRE (1.8.0_192-b12), built on Oct 6 2018 06:46:09…
user1987133
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