GCPerformance.java - Program Output

Java GC Tutorials - Herong's Tutorial Examples

∟Garbage Collection Performance Test Program

∟GCPerformance.java - Program Output

This section describes output data generated by the GC tuning test program - GCPerformance.java.

Before we do any GC performance tests with the GCPerformance.java, let's run it with no wait time and no warmup to review its output:

herong> javac GCPerformance.java

herong> java GCPerformance 1024 32 64 0 0

Parameters: Size=1024KB, Base=32, Chunk=64, Wait=0ms, Warmup=0
Real:Exec  Lat.     Throughput      Total:Free  Proc.
Time:Time  ms/o  Ave:Min:Max:Chunk   Mem.:Mem.   Obj.
  88:88    1375  727:727:727:727   909312:711400   64
           ----              -----               ----
           |                 |                   |- 64 obj. processed
           |                 |- Throughput: 727 objects per second
           |- Latency: 1375 ms per 1000 objects

 143:143  1375  895:727:1163:1163  601088:403076  128
 163:163  1375  1177:727:3200:3200  505856:307832  192
 199:199  1375  1286:727:3200:1777  580608:382614  256
          ----  ----
          |     |- Ave. throughput: 1917 objects per second
          |- Latency: 1375 ms per 1000 objects
...

Note that you may get an "ArithmeticException: / by zero", if you use a low object size and chunk size. For example:

herong> java GCPerformance 1024 32 32 0 0

Parameters: Size=1024KB, Base=32, Chunk=32, Wait=0ms, Warmup=0
Real:Exec  Lat.     Throughput      Total:Free  Proc.
Time:Time  ms/o  Ave:Min:Max:Chunk   Mem.:Mem.   Obj.
47:47  1470  680:680:680:680  362496:230119  32
78:78  1470  820:680:1032:1032  362496:230022  64
93:93  1470  1032:680:2133:2133  362496:230009  96
Exception in thread "main" java.lang.ArithmeticException: / by zero
        at GCPerformance.myTest(GCPerformance.java:61)
        at GCPerformance.main(GCPerformance.java:21)

Descriptions on output columns:

"Real Time" - The elapsed time in seconds since the start of the application.
"Exec Time" - The actual execution time in seconds of the application, calculated as the elapsed time minus waiting time.
"Lat. ms/o" - The latency in milliseconds per 1000 objects.
"Throughput Ave" - The average throughput up to this iteration in objects per second.
"Throughput Min" - The minimum throughput up to this iteration in objects per second.
"Throughput Max" - The maximum throughput up to this iteration in objects per second.
"Throughput Chunk" - The throughput of this iteration chunk in objects per second.
"Total Mem." - The total heap memory size in KB, reported by the totalMemory() method.
"Free Mem." - The free heap memory size available for application in KB, reported by the freeMemory() method.
"Proc. Obj." - The total number objects processed in the test run.

For this running session, the application performance is:

Throughput: 399 objects per seconds
Latency:    3906 milliseconds per 1000 objects

Table of Contents

About This Book

Heap Memory Area and Size Control

JVM Garbage Collection Logging

Introduction of Garbage Collectors

Serial Collector - "+XX:+UseSerialGC"

Parallel Collector - "+XX:+UseParallelGC"

Concurrent Mark-Sweep (CMS) Collector - "+XX:+UseConcMarkSweepGC"

Garbage First (G1) Collector - "+XX:+UseG1GC"

The Z Garbage Collector (ZGC) - "+XX:+UseZGC"

Object References and Garbage Collection

►Garbage Collection Performance Test Program

GCPerformance.java - GC Performance Test Program

►GCPerformance.java - Program Output

Performance Impact of Wait Time

Performance Impact of Object Size

Performance Impact of Chunk Size

Performance Jumps Not Related to GC

Performance Test and System Interruptions

"START /REALTIME" - Run JVM with Highest Priority

GCPerfP99.java - 99th Percentile Performance

GCPerfP99.java - Output Verification

GCPerfP99V2.java - Percentile Performance with Load

GCPerfP99V2.java - Work Load Level

GCPerfP99V2.java - Object Number and Size

Performance Tests on Serial Collector

Performance Tests on Parallel collector

Performance Tests on Concurrent collector

Performance Tests on G1 collector

Garbage Collection Performance Test Summary

References

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