Java profiling Do It Yourself (jug.msk.ru 2016)

Java profiling
Do It Yourself
Alexey Ragozin
alexey.ragozin@gmail.com
JUG.MSK.RU 2016

JVM diagnostic interfaces
• JMX
• JVMTI – native API only
• Attach Protocol
 Ad hoc instrumentation
 and more
• Perf counters
• Heap dump
• Flight recorder
• Serviceability agent

MBeans: threading
 CPU usage per thread (user / sys)
 Memory allocation per thread
 Block / wait times
 Should be enabled
 Stack traces
Invaluable

SJK: ttop
2014-10-01T19:27:22.825+0400 Process summary
process cpu=101.80%
application cpu=100.50% (user=86.21% sys=14.29%)
other: cpu=1.30%
GC cpu=0.00% (young=0.00%, old=0.00%)
heap allocation rate 123mb/s
safe point rate: 0.8 (events/s) avg. safe point pause: 211.69ms
safe point sync time: 0.00% processing time: 17.47% (wallclock time)
[000037] user=83.66% sys=14.02% alloc= 121mb/s - Proxy:ExtendTcpProxyService1:TcpAcceptor:TcpProcessor
[000075] user= 0.97% sys= 0.08% alloc= 411kb/s - RMI TCP Connection(35)-10.139.200.51
[000029] user= 0.61% sys=-0.00% alloc= 697kb/s - Invocation:Management
[000073] user= 0.49% sys=-0.01% alloc= 343kb/s - RMI TCP Connection(33)-10.128.46.114
[000023] user= 0.24% sys=-0.01% alloc= 10kb/s - PacketPublisher
[000022] user= 0.00% sys= 0.10% alloc= 11kb/s - PacketReceiver
[000026] user= 0.12% sys=-0.07% alloc= 2217b/s - Cluster|Member(Id=18, Timestamp=2014-10-01 15:58:3...
[000076] user= 0.00% sys= 0.04% alloc= 6657b/s - JMX server connection timeout 76
[000021] user= 0.00% sys= 0.03% alloc= 526b/s - PacketListener1P
[000034] user= 0.00% sys= 0.02% alloc= 1537b/s - Proxy:ExtendTcpProxyService1
[000049] user= 0.00% sys= 0.02% alloc= 6011b/s - JMX server connection timeout 49
[000032] user= 0.00% sys= 0.01% alloc= 0b/s - DistributedCache
https://github.com/aragozin/jvm-tools/blob/master/sjk-core/COMMANDS.md#ttop-command
Available via PerfCounters

MBeans: memory
• Memory geometry information
• Collection count
• Last collection details
 for each collector
• GC events available as notifications
since Java 7

SJK: GC
[GC: Copy#1806 time: 7ms interval: 332ms mem: Eden Space: 108032k-108032k->0k[max:191168k,rate:-325397.59kb/s] Tenured
Gen: 162185k+14k->162199k[max:477888k,rate:42.22kb/s] Survivor Space: 235k-13k->222k[max:23872k,rate:-41.93kb/s]]
Gen: 162418k+0k->162418k[max:477888k,rate:0.00kb/s] Survivor Space: 1k+0k->1k[max:23872k,rate:0.24kb/s]]
Total
Copy[ collections: 28 | avg: 0.0065 secs | total: 0.2 secs ]
MarkSweepCompact[ collections: 0 | avg: NaN secs | total: 0.0 secs ]
https://github.com/aragozin/jvm-tools/blob/master/sjk-core/COMMANDS.md#gc-command

MBeans: diagnostic commands
com.sun.management:type=DiagnosticCommand
com.sun.management:type=HotSpotDiagnostic
• Forcing GC / GC log rotation
• Head dump
• Flight recorder
• Changing --XX options
• etc
Java 8

JVM Attach Protocol
• List JVM processes
• Attach to JVM by PID
• Send control commands
 heap dump / histogram
 stack dump
• Inspect system properties and VM options
• Launch instrumentation agents
https://github.com/gridkit/jvm-attach

SJK: hh --dead
Dead object histogram
 Similar to jmap –histo
 Invoke jmap –histo two time
 all heap objects
 live heap object
 calculates difference
 Can show top N rows
https://github.com/aragozin/jvm-tools/blob/master/sjk-core/COMMANDS.md#hh-command

SJK: hh --dead
1: 19117456 2038375696 [C
2: 9543865 441272568 [Ljava.lang.Object;
3: 13519356 432619392 java.util.HashMap$Entry
4: 12558262 301398288 java.lang.String
5: 7193066 287722640 org.hibernate.engine.spi.CollectionKey
6: 619253 160678888 [I
7: 4710497 113051928 org.jboss.seam.international.Messages$1$1
8: 571327 100876880 [Ljava.util.HashMap$Entry;
9: 1436183 57447320 org.hibernate.event.spi.FlushEntityEvent
10: 1661932 53181824 java.util.Stack
11: 209899 52047904 [B
12: 1624200 51974400 org.hibernate.engine.internal.Cascade
13: 929354 44608992 java.util.HashMap
14: 1812762 43506288 org.hibernate.i.u.c.IdentityMap$IdentityMapEntry
15: 850157 34006280 java.util.TreeMap$Entry
16: 1044636 25071264 java.util.ArrayList
17: 1340986 23423328 [Ljava.lang.Class;
18: 710973 22751136 java.io.ObjectStreamClass$WeakClassKey
19: 885164 21243936 org.hibernate.event.internal.WrapVisitor
20: 885126 21243024 org.hibernate.event.internal.FlushVisitor
...
Total 95197823 4793878008
https://github.com/aragozin/jvm-tools/blob/master/sjk-core/COMMANDS.md#hh-command

SJK: jps
JDK’s jps on steroid
 Uses attach API
 Lists VMs
 Filtering by JVM system properties
 Prints property values
 Prints effective –XX options
https://github.com/aragozin/jvm-tools/blob/master/sjk-core/COMMANDS.md#jps-command

SJK: jps
My favorite command
> sjk jps -pd PID MAIN duser.dir XMaxHeapSize
90543 sjk-0.3.1-SNAPSHOT.jar /var/vas_sdk_test_server -XX:MaxHeapSize=32126271488
5315 WrapperSimpleApp /var/vas_sdk_test_server/vas-sdk-test-13030 -XX:MaxHeapSize=4294967296
11094 WrapperSimpleApp /var/vas_sdk_test_server/vas-sdk-test-13020 -XX:MaxHeapSize=4294967296
993 Main /var/gedoms-uat/private/rtdb_1 -XX:MaxHeapSize=12884901888
56603 AxiomApplication /var/gedoms-uat/private/gedoms_1 -XX:MaxHeapSize=2147483648
24046 WrapperSimpleApp /var/sonar/sonar-3.6.2/bin/linux-x86-64 -XX:MaxHeapSize=536870912
https://github.com/aragozin/jvm-tools/blob/master/sjk-core/COMMANDS.md#jps-command

Perf counters
 Based on shared memory
 safe for target JVM
 Flat data model
 misc JVM counters
 safepoint statistics
 GC tennuring stats
 you can add own counter programmatically
 jcmd PID PerfCounter.print

Stack Trace Sampling
Capture
• Dump stack traces via local connection
• Store in highly compressed dump
10-30 bytes per trace
Analysis
• Frame frequency
• Conditional frame frequency
• Traces classification histogram
https://github.com/aragozin/jvm-tools/blob/master/sjk-core/COMMANDS.md#stcap-command

Flame Graphs
https://github.com/aragozin/jvm-tools/blob/master/sjk-core/COMMANDS.md#ssa-command

Tracking down CPU hogs
Command
sjk ssa -f tracedump.std --categorize -tf **.CoyoteAdapter.service -nc
JDBC=**.jdbc
Hibernate=org.hibernate
"Facelets compile=com.sun.faces.facelets.compiler.Compiler.compile"
"Seam bijection=org.jboss.seam.**.aroundInvoke/!**.proceed"
JSF.execute=com.sun.faces.lifecycle.LifecycleImpl.execute
JSF.render=com.sun.faces.lifecycle.LifecycleImpl.render
Other=**
Report
Total samples 2732050 100.00%
JDBC 405439 14.84%
Hibernate 802932 29.39%
Facelets compile 395784 14.49%
Seam bijection 385491 14.11%
JSF.execute 290355 10.63%
JSF.render 297868 10.90%
Other 154181 5.64% 0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
Time
Other
JSF.render
JSF.execute
Seam bijection
Facelets compile
Hibernate
JDBC
Excel

Tracking down CPU hogs
Stack frame frequency histogram
Command
sjk ssa -f tracedump --histo -tf **!**.jdbc -tt ogr.hibernate
Report
Trc (%)FrmNTerm (%)Frame
69950687%699506 0 0%org.hibernate.internal.SessionImpl.autoFlushIfRequired(SessionImpl.java:1204)
68937085%689370 10 0%org.hibernate.internal.QueryImpl.list(QueryImpl.java:101)
67652484%676524 0 0%org.hibernate.event.internal.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:58)
67513684%675136 0 0%org.hibernate.internal.SessionImpl.list(SessionImpl.java:1261)
57383671%573836 4 0%org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:264)
55096868%550968 1 0%org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:99)
53389266%533892 132 0%org.hibernate.event.internal.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:227)
38151447%381514 882 0%org.hibernate.event.internal.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:76)
27101833%271018 0 0%org.hibernate.event.internal.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:161)
http://blog.ragozin.info/2016/01/flame-graphs-vs-cold-numbers.html

Working with heap dumps
Java API to traverse heap dump object graph
Available at https://github.com/aragozin/jvm-tools/tree/master/hprof-heap
 Based on NetBeans profiler library
 No temporary files used
 Fixed generic method signatures
 Improved performance
Useful for
 In-place processing of large heap dumps
150 GiB is my personal record
 Write domain specific heap usage reports

HeapPath
 Convenient way to extract value from dump
 Error proof
 Handles String, primitives/boxed and arrays
myfield1.myfield2.myfield3
myarrayfield[0].myfield
myarrayfield[*].myfield
myarrayfield[*][*]
myfield1.*.myfield3
[*].value(MyClass)
myhashmap?entrySet[key=description].value

See also
https://github.com/vlsi/mat-calcite-plugin
Heap dump meets SQL

SJK Summary
Visit https://github.com/aragozin/jvm-tools
 Single executable JAR
 Command line interface
 Exploits JMX/JVMAttachProtocol/PerfCounters
 Sampling profiler included
 Extensible commands
 Write commands for your own application

Btrace: CLI profiler
BTrace
• Instrumenting
profiler
• Used via CLI or API
• Scriptable
with Java
BTrace script
@Property
Profiler prof = Profiling.newProfiler();
@OnMethod(clazz = "org.jboss.seam.Component",
method = "/(inject|disinject|outject)/")
void entryByMethod2(@ProbeClassName String className,
@ProbeMethodName String methodName, @Self Object component) {
if (component != null) {
Field nameField = field(classOf(component), "name", true);
if (nameField != null) {
String name = (String)get(nameField, component);
Profiling.recordEntry(prof, concat("org.jboss.seam.Component.",
concat(methodName, concat(":", name))));
}
}
}
@OnMethod(clazz = "org.jboss.seam.Component",
method = "/(inject|disinject|outject)/",
location = @Location(value = Kind.RETURN))
void exitByMthd2(@ProbeClassName String className,
@ProbeMethodName String methodName, @Self Object component,
@Duration long duration) {
if (component != null) {
Field nameField = field(classOf(component), "name", true);
if (nameField != null) {
String name = (String)get(nameField, component);
Profiling.recordExit(prof, concat("org.jboss.seam.Component.",
concat(methodName, concat(":", name))), duration);
}
}
}
https://github.com/jbachorik/btrace2

Sigar
System Information Gatherer And Reporter
https://github.com/hyperic/sigar
• Cross platform
• Common system metrics
 CPU, Context switches, IO, etc
• Java bindings
 Self extracting JAR: org.gridkit.lab:sigar-lib:1.6.4

Flight Recorder
+ Accessible via JMX
+ Targeting JVM internals
+ Low overhead
‐ Non-compact file format
‐ Biased profiling
‐ Weak support for thread sampling

Serviceability agent
Ultimate JVM debugging tool
• Use binding to platform debugger (windbg, gdbg)
can work with core dumps
• Use RTTI information from JVM binaries
OpenJDK requires debug symbols to be installed for SA to work
• Introspect JVM internals by inspecting process memory
• Used by jstack -F and other JVM tools accepting core dumps
• Very buggy!
• Very slow!
• Abandoned?

Mixed Stack Sampling
Sampling via SA
• Sample all Java, JVM and native
• Slow (~10 times application slow down)

Serviceability Agent Summary
Hybrid stack trace sampling
• Slow and intrusive
• Stack parsing issues (-XX:+PreserveFramePointer should help)
• There are alternatives:
Honest Profiler - https://github.com/RichardWarburton/honest-profiler
Perf Map Agent - https://github.com/jrudolph/perf-map-agent
Heap walking with SA
• May be faster for large heaps
No need heap to disk serialization!
• Inspecting portion of heap (e.g. Eden only)
• Some code in jdi-sa.jar should be optimized to fix performance

Thank you
Alexey Ragozin
alexey.ragozin@gmail.com
http://blog.ragozin.info
- my technical blog
http://github.com/aragozin
http://github.com/gridkit
- my open source projects

Java profiling Do It Yourself (jug.msk.ru 2016)

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