| 1 | Header for -agentlib:hprof (or -Xrunhprof) ASCII Output (JDK 5.0 JVMTI based)
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| 2 |
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| 3 | @(#)jvm.hprof.txt 1.5 06/01/28
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| 4 |
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| 5 | Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
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| 6 |
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| 7 | WARNING! This file format is under development, and is subject to
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| 8 | change without notice.
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| 9 |
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| 10 | This file contains the following types of records:
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| 11 |
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| 12 | THREAD START
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| 13 | THREAD END mark the lifetime of Java threads
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| 14 |
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| 15 | TRACE represents a Java stack trace. Each trace consists
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| 16 | of a series of stack frames. Other records refer to
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| 17 | TRACEs to identify (1) where object allocations have
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| 18 | taken place, (2) the frames in which GC roots were
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| 19 | found, and (3) frequently executed methods.
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| 20 |
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| 21 | HEAP DUMP is a complete snapshot of all live objects in the Java
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| 22 | heap. Following distinctions are made:
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| 23 |
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| 24 | ROOT root set as determined by GC
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| 25 | CLS classes
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| 26 | OBJ instances
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| 27 | ARR arrays
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| 28 |
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| 29 | SITES is a sorted list of allocation sites. This identifies
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| 30 | the most heavily allocated object types, and the TRACE
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| 31 | at which those allocations occurred.
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| 32 |
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| 33 | CPU SAMPLES is a statistical profile of program execution. The VM
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| 34 | periodically samples all running threads, and assigns
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| 35 | a quantum to active TRACEs in those threads. Entries
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| 36 | in this record are TRACEs ranked by the percentage of
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| 37 | total quanta they consumed; top-ranked TRACEs are
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| 38 | typically hot spots in the program.
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| 39 |
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| 40 | CPU TIME is a profile of program execution obtained by measuring
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| 41 | the time spent in individual methods (excluding the time
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| 42 | spent in callees), as well as by counting the number of
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| 43 | times each method is called. Entries in this record are
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| 44 | TRACEs ranked by the percentage of total CPU time. The
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| 45 | "count" field indicates the number of times each TRACE
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| 46 | is invoked.
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| 47 |
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| 48 | MONITOR TIME is a profile of monitor contention obtained by measuring
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| 49 | the time spent by a thread waiting to enter a monitor.
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| 50 | Entries in this record are TRACEs ranked by the percentage
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| 51 | of total monitor contention time and a brief description
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| 52 | of the monitor. The "count" field indicates the number of
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| 53 | times the monitor was contended at that TRACE.
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| 54 |
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| 55 | MONITOR DUMP is a complete snapshot of all the monitors and threads in
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| 56 | the System.
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| 57 |
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| 58 | HEAP DUMP, SITES, CPU SAMPLES|TIME and MONITOR DUMP|TIME records are generated
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| 59 | at program exit. They can also be obtained during program execution by typing
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| 60 | Ctrl-\ (on Solaris) or by typing Ctrl-Break (on Win32).
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