PHAT parse java's hprof (dump) files, like jhat

Motivation

I wrote this to successfully parse a java heap dumps that jhat was incapable of. The problem I kept hitting was that I couldn't make the heap large enough for jhat to successfully parse the dump files that were being generated. The root cause for jhat was that it used java.util.HashMap to store classes and instances, and it exhausted all of memory parsing the file, even with a 64-bit JVM.

Unlike jhat, phat parses the dump file, storing classes and instances in a red/black tree, similar to java.util.TreeMap. Since it's written in C, you don't have to guess the heap allocation.

Output

• Dump file created [... date ...]
• trace back frames
• Heap Summary
• Class Summary
• Instance Summary

Dump file date

The heap dump creation date.

trace back frames

tracebacks for each thread

Heap Summary

        root thread :       79 
        root global :       35 
         root local :       33 
         root frame :      712 
              stack :        0 
       system class :     3335 
       thread block :        0 
            monitor :        8 
              class :    11829 
           instance :  5767989 
       object array :   795709 
      primary array :   979154 

Class Summary

- Class Identifier
- Name Identifier 
- count of instances
- symbol class name

    0x2678c7a8 class 0x530fc950 3 java/util/concurrent/atomic/AtomicLongFieldUpdater$CASUpdater
    0x2678c808 class 0x54196eb0 0 java/util/concurrent/ExecutionException
    0x2678c928 class 0x5634e890 0 java/util/UUID$Holder
    0x2678ca48 class 0x541c2860 0 java/util/JumboEnumSet
    0x2678d8e8 class 0x53129728 2 java/util/Collections$SynchronizedSortedMap
    0x2678df48 class 0x54d8b8e8 3 java/util/TaskQueue
    0x2678dfa8 class 0x54d86258 0 java/util/TooManyListenersException
    0x26993e50 class 0x55583a20 3 java/util/Timer

Instance Summary

Instance 0x28405f00 of 0x26993e50 java/util/Timer self 12 self+children -1293452014923129306
      0 (  0): L threadReaper              Instance 0x28614b10 of 0x295e0660 java/util/Timer$1 self 4 self+children 4
            ----> (1)
              0 (  0): L this$0                    [ recursive ] Instance 0x28405f00 of 0x26993e50 self 12 self+children -729915866
            <---- (1)
      1 (  4): L thread                    Instance 0x267a7300 of 0x295e06b8 java/util/TimerThread self 112 self+children -1293452014923129842
            ----> (1)
              0 (  5): I threadLocalRandomSecondarySeed  0  0x0
              1 (  9): I threadLocalRandomProbe     0  0x0
              2 ( 13): J threadLocalRandomSeed      0  0x0
              3 ( 21): L uncaughtExceptionHandler  [null]
              4 ( 25): L blockerLock                          5 ( 29): L blocker                   [null]
              6 ( 33): L parkBlocker               [null]
              7 ( 37): I threadStatus               401  0x191
              8 ( 41): J tid                        50  0x32
              9 ( 49): J nativeParkEventPointer     0  0x0
             10 ( 57): J stackSize                  0  0x0
             11 ( 65): L inheritableThreadLocals             12 ( 69): L threadLocals              [null]
             13 ( 73): L inheritedAccessControlContext               14 ( 77): L contextClassLoader                  15 ( 81): L group                               16 ( 85): L target                    [null]
             17 ( 89): Z stillborn                  0  0x0
             18 ( 90): Z daemon                     1  0x1
             19 ( 91): Z single_step                0  0x0
             20 ( 92): J eetop                      1424803840  0x54ecc800
             21 (100): L threadQ                   [null]
             22 (104): I priority                   5  0x5
             23 (108): L name                                24 (  0): L queue                               25 (  4): Z newTasksMayBeScheduled     1  0x1
            <---- (1)
      2 (  8): L queue                     Instance 0x29151e00 of 0x2678df48 java/util/TaskQueue self 8 self+children 520
            ----> (1)
              0 (  0): I size                       0  0x0
              1 (  4): L queue                              <---- (1)

Usage

- Generate a class instance list with counts

phat  heapdump.heap  > heapdump.out
egrep ' class ' heapdump.out | sort -n -k 4 > heapdump.out.s


- Dump details on a specific class

phat  -C java/util/TaskQueue  heapdump.heap  > heapinfo

Options

• '-C' dump details on specific class
• '-d' print diagnostic debugging for development
• '-l' limit class dump depth

Limitations

• recursive dump of classes needs some pretty-printing work
• consider sorting of classes within the app
• limit of the nubmer elements in array object to print should be configurable (100)