1. Introduction to GCViewer

Two tools for analyzing GC logs are more popular in the industry - GCViewer and GCEasy. Some functions of GCEasy still need to be charged. Today I will introduce the use and function of GCViewer to you. Memory Analyzer Mat JVM Analysis

2. Use of GCViewer

2.1 compile

GitHub - chewiebug/GCViewer at 1.36

First, search for the GCViewer project on github and download it locally. The GCViewer project does not provide a ready-made release version. Use the following maven compilation command to complete the compilation of GCViewer and finally generate a gcviewer-1.36.jar.

yum install  -y  git  svn  maven
cd  /hadoop/software/
unzip  GCViewer-1.36.zip
cd  GCViewer-1.36
## maven 编译 操作环境 Linux 
mvn clean install -DskipTests

2.2 use

Double-click the compiled jar

Full GC Lines：（full gc）
Inc GC Lines: (incremental GC)
GC Times Line: (gc time)
GC Times Rectangles: (gc time zone)
Total Heap: (total heap size)
Red line that shows heap size
Tenured Generation: (Old Generation)
Young Generation: (young generation)
Used Heap: (heap usage)
Initial mark level: (cms or g1 garbage collection algorithm initial mark event)
Concurrent collections: (cms or g1 garbage collection concurrent collection cycle)

Run the Java program to print the GC log, the garbage collector uses G1

/usr/java/jdk1.8.0_144/bin/java \
  -Xmx1024m -Xms1024m -XX:+UseG1GC -XX:MaxGCPauseMillis=100 \
  -XX:-ResizePLAB -verbose:gc -XX:-PrintGCCause -XX:+PrintAdaptiveSizePolicy \
  -XX:+PrintGCDetails -XX:+PrintGCDateStamps -Xloggc:/hadoop/datadir/windeploy/log/ETL/DS/gc.log-`date +'%Y%m%d%H%M'` \
  -classpath xxx.jar

GC logs will be generated in the path /hadoop/datadir/windeploy/log/ETL/DS/, and some of the generated logs are as follows:

2022-11-23T15:33:14.532+0800: 27253.342: [GC concurrent-root-region-scan-start]
2022-11-23T15:33:14.540+0800: 27253.350: [GC concurrent-root-region-scan-end, 0.0077278 secs]
2022-11-23T15:33:14.540+0800: 27253.350: [GC concurrent-mark-start]
2022-11-23T15:33:16.881+0800: 27255.691: [GC concurrent-mark-end, 2.3412370 secs]
2022-11-23T15:33:16.881+0800: 27255.691: [GC remark 2022-11-23T15:33:16.881+0800: 27255.691: [Finalize Marking, 0.0001521 secs] 2022-11-23T15:33:16.882+0800: 27255.692: [GC ref-proc, 0.0006298 secs] 2022-11-23T15:33:16.882+0800: 27255.692: [Unloading, 0.0118105 secs], 0.0180534 secs]
 [Times: user=0.04 sys=0.00, real=0.02 secs] 
2022-11-23T15:33:16.900+0800: 27255.710: [GC cleanup 925M->925M(1024M), 0.0041387 secs]
 [Times: user=0.01 sys=0.00, real=0.00 secs] 
2022-11-23T15:34:15.075+0800: 27313.885: [GC pause (young) 27313.885: [G1Ergonomics (CSet Construction) start choosing CSet, _pending_cards: 2602, predicted base time: 3.19 ms, remaining time: 96.81 ms, target pause time: 100.00 ms]
 27313.885: [G1Ergonomics (CSet Construction) add young regions to CSet, eden: 45 regions, survivors: 6 regions, predicted young region time: 7.09 ms]
 27313.885: [G1Ergonomics (CSet Construction) finish choosing CSet, eden: 45 regions, survivors: 6 regions, old: 0 regions, predicted pause time: 10.28 ms, target pause time: 100.00 ms]
 27313.895: [G1Ergonomics (Concurrent Cycles) do not request concurrent cycle initiation, reason: still doing mixed collections, occupancy: 941621248 bytes, allocation request: 0 bytes, threshold: 483183810 bytes (45.00 %), source: end of GC]
 27313.895: [G1Ergonomics (Mixed GCs) do not start mixed GCs, reason: reclaimable percentage not over threshold, candidate old regions: 8 regions, reclaimable: 2873312 bytes (0.27 %), threshold: 5.00 %]
, 0.0100596 secs]
   [Parallel Time: 8.9 ms, GC Workers: 4]
      [GC Worker Start (ms): Min: 27313885.0, Avg: 27313887.0, Max: 27313888.9, Diff: 4.0]
      [Ext Root Scanning (ms): Min: 0.0, Avg: 0.6, Max: 1.2, Diff: 1.2, Sum: 2.2]
      [Update RS (ms): Min: 0.0, Avg: 1.3, Max: 2.6, Diff: 2.6, Sum: 5.2]
         [Processed Buffers: Min: 0, Avg: 3.5, Max: 10, Diff: 10, Sum: 14]
      [Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Object Copy (ms): Min: 4.9, Avg: 5.0, Max: 5.1, Diff: 0.2, Sum: 20.1]
      [Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
         [Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [GC Worker Total (ms): Min: 4.9, Avg: 6.9, Max: 8.9, Diff: 4.0, Sum: 27.6]
      [GC Worker End (ms): Min: 27313893.9, Avg: 27313893.9, Max: 27313893.9, Diff: 0.0]
   [Code Root Fixup: 0.1 ms]
   [Code Root Purge: 0.0 ms]
   [Clear CT: 0.1 ms]
   [Other: 1.0 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 0.7 ms]
      [Ref Enq: 0.0 ms]
      [Redirty Cards: 0.0 ms]
      [Humongous Register: 0.0 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 0.1 ms]
   [Eden: 45.0M(45.0M)->0.0B(46.0M) Survivors: 6144.0K->5120.0K Heap: 944.1M(1024.0M)->899.8M(1024.0M)]
 [Times: user=0.03 sys=0.00, real=0.01 secs] 
2022-11-23T15:34:15.631+0800: 27314.441: [GC pause (young) 27314.441: [G1Ergonomics (CSet Construction) start choosing CSet, _pending_cards: 4127, predicted base time: 4.55 ms, remaining time: 95.45 ms, target pause time: 100.00 ms]
 27314.441: [G1Ergonomics (CSet Construction) add young regions to CSet, eden: 46 regions, survivors: 5 regions, predicted young region time: 6.81 ms]
 27314.441: [G1Ergonomics (CSet Construction) finish choosing CSet, eden: 46 regions, survivors: 5 regions, old: 0 regions, predicted pause time: 11.36 ms, target pause time: 100.00 ms]
 27314.450: [G1Ergonomics (Concurrent Cycles) request concurrent cycle initiation, reason: occupancy higher than threshold, occupancy: 942669824 bytes, allocation request: 0 bytes, threshold: 483183810 bytes (45.00 %), source: end of GC]
, 0.0093238 secs]
   [Parallel Time: 8.6 ms, GC Workers: 4]
      [GC Worker Start (ms): Min: 27314441.0, Avg: 27314441.0, Max: 27314441.0, Diff: 0.0]
      [Ext Root Scanning (ms): Min: 0.6, Avg: 0.7, Max: 0.7, Diff: 0.1, Sum: 2.7]
      [Update RS (ms): Min: 2.3, Avg: 2.5, Max: 2.7, Diff: 0.4, Sum: 9.9]
         [Processed Buffers: Min: 3, Avg: 5.2, Max: 9, Diff: 6, Sum: 21]
      [Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Object Copy (ms): Min: 5.1, Avg: 5.3, Max: 5.5, Diff: 0.4, Sum: 21.4]
      [Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
         [Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [GC Worker Total (ms): Min: 8.5, Avg: 8.5, Max: 8.5, Diff: 0.0, Sum: 34.1]
      [GC Worker End (ms): Min: 27314449.5, Avg: 27314449.5, Max: 27314449.5, Diff: 0.0]
   [Code Root Fixup: 0.1 ms]
   [Code Root Purge: 0.0 ms]
   [Clear CT: 0.0 ms]
   [Other: 0.7 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 0.3 ms]
      [Ref Enq: 0.0 ms]
      [Redirty Cards: 0.0 ms]
      [Humongous Register: 0.0 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 0.1 ms]
   [Eden: 46.0M(46.0M)->0.0B(44.0M) Survivors: 5120.0K->7168.0K Heap: 945.8M(1024.0M)->903.2M(1024.0M)]
 [Times: user=0.03 sys=0.00, real=0.01 secs] 
 27374.524: [G1Ergonomics (Concurrent Cycles) request concurrent cycle initiation, reason: occupancy higher than threshold, occupancy: 942669824 bytes, allocation request: 589840 bytes, threshold: 483183810 bytes (45.00 %), source: concurrent humongous allocation]
 27374.525: [G1Ergonomics (Concurrent Cycles) request concurrent cycle initiation, reason: requested by GC cause, GC cause: G1 Humongous Allocation]
 27374.525: [G1Ergonomics (Concurrent Cycles) initiate concurrent cycle, reason: concurrent cycle initiation requested]
2022-11-23T15:35:15.715+0800: 27374.525: [GC pause (young) (initial-mark) 27374.525: [G1Ergonomics (CSet Construction) start choosing CSet, _pending_cards: 1557, predicted base time: 3.33 ms, remaining time: 96.67 ms, target pause time: 100.00 ms]
 27374.525: [G1Ergonomics (CSet Construction) add young regions to CSet, eden: 12 regions, survivors: 7 regions, predicted young region time: 4.48 ms]
 27374.525: [G1Ergonomics (CSet Construction) finish choosing CSet, eden: 12 regions, survivors: 7 regions, old: 0 regions, predicted pause time: 7.81 ms, target pause time: 100.00 ms]
, 0.0065173 secs]
   [Parallel Time: 5.7 ms, GC Workers: 4]
      [GC Worker Start (ms): Min: 27374524.8, Avg: 27374524.8, Max: 27374524.8, Diff: 0.0]
      [Ext Root Scanning (ms): Min: 0.7, Avg: 0.8, Max: 0.8, Diff: 0.1, Sum: 3.0]
      [Update RS (ms): Min: 0.5, Avg: 0.6, Max: 0.9, Diff: 0.4, Sum: 2.5]
         [Processed Buffers: Min: 1, Avg: 2.2, Max: 5, Diff: 4, Sum: 9]
      [Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Object Copy (ms): Min: 4.0, Avg: 4.2, Max: 4.3, Diff: 0.4, Sum: 16.9]
      [Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
         [Termination Attempts: Min: 1, Avg: 1.0, Max: 1, Diff: 0, Sum: 4]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [GC Worker Total (ms): Min: 5.6, Avg: 5.6, Max: 5.7, Diff: 0.0, Sum: 22.6]
      [GC Worker End (ms): Min: 27374530.4, Avg: 27374530.4, Max: 27374530.4, Diff: 0.0]
   [Code Root Fixup: 0.0 ms]
   [Code Root Purge: 0.0 ms]
   [Clear CT: 0.0 ms]
   [Other: 0.7 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 0.4 ms]
      [Ref Enq: 0.0 ms]
      [Redirty Cards: 0.0 ms]
      [Humongous Register: 0.0 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 0.0 ms]
   [Eden: 12.0M(44.0M)->0.0B(49.0M) Survivors: 7168.0K->2048.0K Heap: 915.2M(1024.0M)->901.1M(1024.0M)]
 [Times: user=0.02 sys=0.00, real=0.00 secs]

I use GCView to open the GC log , and I can see that as the heap usage gets higher and higher, Full GC triggers frequently

Summary、Memory、Pause

The process runs for 8+h.
The maximum utilization rate of the heap reaches 100%.

The maximum usage rate of the old generation reaches 105.2%.
The maximum utilization rate of the new generation reaches 100%.

This tool is only a basic analysis of memory, and does not have detailed large object information, so I found this tool Memory Analyzer Mat again. Memory Analyzer Mat JVM Analysis

Thanks for likes and attention!

Introduction to the use of GC view, a tool for GC log analysis

1. Introduction to GCViewer

2. Use of GCViewer

2.1 compile

2.2 use

Thanks for likes and attention!

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