Jstat Monitoring and Tuning GC is very useful

The Jstat command uses

The Jstat command can see how much of the heap memory is being used, and how many classes are loaded. The format of the command is as follows:

Jstat [-Command options] [Vmid] [interval time/MS] [query count]

Note: The JDK version used is jdk8.

Class Load Statistics:

C:\Users\Administrator>jstat -class 2060Loaded Bytes Unloaded Bytes Time 15756 17355.6 0 0.0 11.29

• 1
• 2
• 3

• 1
• 2
• 3

• Loaded: The number of loaded class
• Bytes: The amount of space occupied
• Unloaded: Quantity not loaded
• Bytes: Unoccupied Space not loaded
• Time:

Compiling statistics

C:\Users\Administrator>jstat -compiler 2060Compiled Failed Invalid   Time   FailedType FailedMethod    9142      1 0 5.01 1 org/apache/felix/resolver/ResolverImpl mergeCandidatePackages

• 1
• 2
• 3

• 1
• 2
• 3

• Compiled: Number of compilations.
• Failed: Number of failures
• Invalid: Quantity Not Available
• Time:
• Failedtype: Failure type
• Failedmethod: Method of failure

Garbage collection Statistics

C:\Users\Administrator>jstat -gc 2060 S0C    S1C    S0U    S1U      EC       EU        OC         OU          MC     MU    CCSC      CCSU   YGC     YGCT    FGC    FGCT     GCT20480.0 20480.0  0.0   13115.3 163840.0 113334.2  614400.0   436045.7  63872.0 61266.5  0.0    0.0      149    3.440   8      0.295    3.735

• 1
• 2
• 3

• 1
• 2
• 3

• S0C: The size of the first surviving area
• S1C: The size of the second surviving area
• S0U: The use size of the first surviving area
• S1U: The use size of the second surviving area
• EC: Size of the Eden District
• EU: The use of the Eden area size
• OC: old age Size
• OU: old age Use size
• MC: Method Area Size
• MU: Method Area Use size
• CCSC: Compression class space size
• CCSU: Compression class space usage size
• YGC: Number of young generations of garbage collection
• YGCT: Waste collection time for young generation
• FGC: Garbage collection times in the old age
• FGCT: Time spent on garbage collection in the old age
• GCT: Total time spent on garbage collection

Heap Memory statistics

C:\Users\Administrator>jstat -gccapacity 2060 NGCMN    NGCMX     NGC     S0C     S1C       EC      OGCMN      OGCMX       OGC         OC          MCMN     MCMX      MC     CCSMN    CCSMX     CCSC    YGC    FGC204800.0 204800.0 204800.0 20480.0 20480.0 163840.0   614400.0   614400.0   614400.0   614400.0      0.0    63872.0  63872.0      0.0      0.0      0.0    149     8

• 1
• 2
• 3

• 1
• 2
• 3

• NGCMN: Cenozoic Minimum capacity
• NGCMX: Maximum capacity of the Cenozoic
• NGC: Current Cenozoic capacity
• S0C: Size of the first surviving area
• S1C: The size of the second surviving area
• EC: Size of the Eden District
• OGCMN: The old age minimum capacity
• OGCMX: Maximum capacity of the old age
• OGC: Current old age size
• OC: Current old age size
• MCMN: Minimum meta-data capacity
• MCMX: Maximum meta data capacity
• MC: Current meta-data space size
• CCSMN: Minimum compression class space size
• Ccsmx: Maximum compression class space size
• CCSC: Current Compression class space size
• YGC: Young Generation GC Number
• FGC: Number of GC times in the old age

New Generation garbage Collection statistics

C:\Users\Administrator>jstat -gcnew 7172 S0C    S1C    S0U    S1U   TT MTT  DSS      EC       EU     YGC     YGCT40960.0 40960.0 25443.1    0.0 15  15 20480.0 327680.0 222697.8     12    0.736

• 1
• 2
• 3

• 1
• 2
• 3

• S0C: Size of the first surviving area
• S1C: The size of the second surviving area
• S0U: The use size of the first surviving area
• S1U: The use size of the second surviving area
• TT: Number of objects surviving in the Cenozoic
• MTT: Maximum number of objects surviving in the Cenozoic
• DSS: Desired Surviving area size
• EC: Size of the Eden District
• EU: The use of the Eden area size
• YGC: Number of young generations of garbage collection
• YGCT: Waste collection time for young generation

Cenozoic Memory Statistics

C:\Users\Administrator>jstat -gcnewcapacity 7172  NGCMN      NGCMX       NGC      S0CMX     S0C     S1CMX     S1C       ECMX        EC      YGC   FGC  409600.0   409600.0   409600.0  40960.0  40960.0  40960.0  40960.0   327680.0   327680.0    12     0

• 1
• 2
• 3

• 1
• 2
• 3

• NGCMN: Cenozoic Minimum capacity
• NGCMX: Maximum capacity of the Cenozoic
• NGC: Current Cenozoic capacity
• S0CMX: Maximum surviving 1 zone size
• S0C: Currently surviving 1 area size
• S1CMX: Maximum surviving 2 zone size
• S1C: Currently surviving 2 area size
• ECMX: Max Eden Area Size
• EC: Current Eden Area Size
• YGC: Number of young generations of garbage collection
• FGC: Number of recoveries in the old age

Garbage collection statistics in the old age

C:\Users\Administrator>jstat -gcold 7172   MC       MU      CCSC     CCSU       OC          OU       YGC    FGC    FGCT     GCT 33152.0  31720.8      0.0      0.0    638976.0    184173.0     12     0    0.000    0.736

• 1
• 2
• 3

• 1
• 2
• 3

• MC: Method Area Size
• MU: Method Area Use size
• CCSC: Compression class space size
• CCSU: Compression class space usage size
• OC: old age Size
• OU: old age Use size
• YGC: Number of young generations of garbage collection
• FGC: Garbage collection times in the old age
• FGCT: Time spent on garbage collection in the old age
• GCT: Total time spent on garbage collection

Memory statistics for the old age

C:\Users\Administrator>jstat -gcoldcapacity 7172   OGCMN       OGCMX        OGC         OC       YGC   FGC    FGCT     GCT   638976.0    638976.0    638976.0    638976.0    12     0    0.000    0.736

• 1
• 2
• 3

• 1
• 2
• 3

• OGCMN: The old age minimum capacity
• OGCMX: Maximum capacity of the old age
• OGC: Current old age size
• OC: old age Size
• YGC: Number of young generations of garbage collection
• FGC: Garbage collection times in the old age
• FGCT: Time spent on garbage collection in the old age
• GCT: Total time spent on garbage collection

Meta Data Spatial statistics

C:\Users\Administrator>jstat -gcmetacapacity 7172   MCMN       MCMX        MC       CCSMN      CCSMX       CCSC     YGC   FGC    FGCT     GCT   0.0    33152.0    33152.0        0.0        0.0        0.0    12     0    0.000    0.736

• 1
• 2
• 3

• 1
• 2
• 3

• MCMN: Minimum meta-data capacity
• MCMX: Maximum meta data capacity
• MC: Current meta-data space size
• CCSMN: Minimum compression class space size
• Ccsmx: Maximum compression class space size
• CCSC: Current Compression class space size
• YGC: Number of young generations of garbage collection
• FGC: Garbage collection times in the old age
• FGCT: Time spent on garbage collection in the old age
• GCT: Total time spent on garbage collection

Summarize garbage collection statistics

C:\Users\Administrator>jstat -gcutil 7172  S0     S1     E      O      M     CCS    YGC     YGCT    FGC    FGCT     GCT 62.12 0.00 81.36 28.82 95.68 - 12 0.736 0 0.000 0.736

• 1
• 2
• 3

• 1
• 2
• 3

• S0: Survival Zone 1 Current usage ratio
• S1: Survival Zone 2 Current usage ratio
• E: Eden Area usage ratio
• O: Proportions used in the old age
• M: Meta data Area usage scale
• CCS: Compression usage ratio
• YGC: Number of young generations of garbage collection
• FGC: Garbage collection times in the old age
• FGCT: Time spent on garbage collection in the old age
• GCT: Total time spent on garbage collection

JVM Compilation Method Statistics

7172Compiled  Size  Type Method    4608     16    1 org/eclipse/emf/common/util/SegmentSequence$SegmentSequencePool$SegmentsAccessUnit reset

• 1
• 2
• 3

• 1
• 2
• 3

• Compiled: Number of recently compiled methods
• Size: Number of bytecode for the most recently compiled method
• Type: The compilation types of the most recently compiled methods.
• Method: Name identification.

Jstat Monitoring and Tuning GC is very useful