Adaptive Size Policy Changed Survivor Space

This section provides a tutorial on how Adaptive Size Policy used by the Parallel collector changed the survivor space in the Young generation.

In GC log example presented in the last tutorial, the Adaptive Size Policy of the Parallel collector suggested to keep Young generation size as is.

In this tutorial, we will look at GC log example from the test that suggests to change the survivor space size:

982   1048576000   818726112   229849888
0.421: Application time: 0.0250769 seconds

    UseAdaptiveSizePolicy actions to meet  *** throughput goal ***
                       GC overhead (%)
    Young generation:       15.71	  (attempted to grow)
    Tenured generation:      0.00	  (no change)
    Tenuring threshold:    
       (attempted to decrease to avoid survivor space overflow) = 7
{Heap before GC invocations=5 (full 0):
 PSYoungGen      total 409600K, used 224450K [...
  eden space 204800K, 99% used [0x2a000000,0x367f09b0,0x36800000)
  from space 204800K, 9% used [0x43000000,0x44340170,0x4f800000)
  to   space 204800K, 0% used [0x36800000,0x36800000,0x43000000)
 ParOldGen       total 614400K, used 12K [...
0.422: [GC (Allocation Failure) 

   -- Message generated by -XX:+PrintAdaptiveSizePolicy
   AdaptiveSizePolicy::update_averages:  survived: 19145040  
      promoted: 4096  overflow: false
   AdaptiveSizeStart: 0.429 collection: 5 
     avg_survived_padded_avg: 20858680.000000  
     avg_promoted_padded_avg: 4379.852539  
     avg_pretenured_padded_avg: 0.000000  
     tenuring_thresh: 6  target_size: 20971520
   -- Suggested to set tenuring threshold to 6
   -- Suggested to set survivor space to 20971520
   PSAdaptiveSizePolicy::compute_eden_space_size limits: 
      desired_eden_size: 419430400 old_eden_size: 209715200 
      eden_limit: 209715200 cur_eden: 209715200 
      max_eden_size: 209715200 avg_young_live: 18728788
   -- Suggested to increase "eden" to 419430400
      costs minor_time: 0.170889 major_cost: 0.000000 
      mutator_cost: 0.829111 throughput_goal: 0.990000 
      live_space: 287164244 free_space: 419430400 
      old_eden_size: 209715200 desired_eden_size: 209715200
   -- Suggested to keep "eden" as 209715200
   AdaptiveSizePolicy::survivor space sizes: collection: 5 
      (209715200, 209715200) -> (209715200, 20971520) 
   -- Changed survivor spaces to (209715200, 20971520)!
   AdaptiveSizeStop: collection: 5 
[PSYoungGen: 224450K->18696K(409600K)] 
   224462K->18712K(1024000K), 0.0261534 secs]
Heap after GC invocations=5 (full 0):
 PSYoungGen      total 409600K, used 18696K [...
  eden space 204800K, 0% used [0x2a000000,0x2a000000,0x36800000)
  from space 204800K, 9% used [0x36800000,0x37a42150,0x43000000)
  to   space 20480K, 0% used [0x4e400000,0x4e400000,0x4f800000)
   -- "to" space decreased to from 204800K to 20480K!
 ParOldGen       total 614400K, used 16K [...
0.448: Total time for which application threads were stopped: 0.0267686 s 
983   1048576000   1028365984   20210016

As you can see, the "to" survivor space was decreased from 204800K to 20480K based on the Adaptive Size Policy suggestion. May be it is trying to lower the Minor GC time and increase Major GC time.

Last update: 2018.

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"

 What Is Parallel Collector

 Parallel Collector GC Log Message Format

 "-XX:+PrintGCTaskTimeStamps" - Print GC Threads

 "-XX:ParallelGCThreads=n" - # of Threads

 Parallel Collector Stops Application for Minor/Major GC

 PSYoungGen Collector Using Tenuring Age

 Parallel Collector Changing NewRatio and SurvivorRatio

 Parallel Collector Adaptive Size Policy

 Adaptive Size Policy Log Messages

 "-XX:+PrintAdaptiveSizePolicy" - Minor GC Report

Adaptive Size Policy Changed Survivor Space

 Adaptive Size Policy Changed Eden Space

 Adaptive Size Policy for Best Latency

 Adaptive Size Policy for Best Throughput

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

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

 Object References and Garbage Collection

 Garbage Collection Performance Test Program

 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

 Outdated Tutorials


 Full Version in PDF/EPUB