JVM Tuning & Profiling 

P E R F O R M A N C E T U N I N G

C A T A L O G

C A T A L O G @ S N A P D E A L . C O M

Overview

C A T A L O G@ S N A P D E A L . C O M H

Heap Structure

C A T A L O G@ S N A P D E A L . C O M H

GC ProcessObject AllocationFilling up EdenCopying Referenced ObjectsObject AgingAdditional AgingPromotion

C A T A L O G@ S N A P D E A L . C O M

HeapGC OVERHEAD

SURVIVOR SPACE

GC in java - a background job it will involve overheadCan be made faster by using parallelismCan be made faster by reducing heap size - at the cost of more frequent collections and reduced throughput

Helpful in buffering objects so as more and more objectsage expire in young gen as far as possible Main tunable - Survivor size & max age count

C A T A L O G@ S N A P D E A L . C O M

Common Heap Switches-Xms - Sets Initial Heap Size-Xmx - Sets Max Heap-Xmn - Young Gen Size-XX:PermSize - Start Perm Gen -XX:MaxPermSize - Max Perm Gen-XX:+UseSerialGC - Depricated-XX:+UseParallelGC - -XX:+UseParallelOldGC-XX:+UseConcMarkSweepGC

C A T A L O G@ S N A P D E A L . C O M

Common Heap Switches

-XX:ParallelGCThreads-XX:ParallelCMSThreads-XX:+UseG1GC - New Gen collector-XX:CMSInitiatingOccupancyFraction-XX:MaxTenuringThreshold=15-XX:SurvivorRatio=8

C A T A L O G@ S N A P D E A L . C O M

Common Heap Switches

-XX:ParallelGCThreads-XX:ParallelCMSThreads-XX:+UseG1GC - New Gen collectorCMSInitiatingOccupancyFraction-XX:MaxTenuringThreshold=1-XX:SurvivorRatio=8-XX:+PrintGCDetails

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Tuning JVM HeapTradeoff  - Responsiveness vs Throughput

Our Tuning Strategy - Read & Write

More the young gen - less promotions & more throughputMore Parallelism in old gen collector - more fragmentation

Admin Nodes - Throughput driven Web - Better latency for good 99, 95% iles

C A T A L O G@ S N A P D E A L . C O M

Issues faced

C A T A L O G@ S N A P D E A L . C O M

Profiling ToolsVisualVM - Monitor

C A T A L O G@ S N A P D E A L . C O M H

Profiling ToolsVisualVM - Sampler/Profiler - Threads

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Profiling ToolsVisualVM-Sampler/Profiler - CPU Hotspots

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Profiling ToolsVisualGC - Realtime Heap Graphs

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Profiling ToolsJava Mission Control-JVM Debugging in detail

C A T A L O G@ S N A P D E A L . C O M H

Profiling ToolsSjk- Java Swiss Knife - CPU Profiling

C A T A L O G@ S N A P D E A L . C O M

Profiling ToolsSjk- Java Swiss Knife - GC

 SSA & STCAP

 IOSTAT - Disk Stats

SSA - used for taking continuous stack trace dumpTakes thread dump in super dense filesCan be analyzed using stcapstcap - can be used to print complete trace or histogram

C A T A L O G@ S N A P D E A L . C O M H

Profiling Toolsiostat -x 1 100 vda vmstat # pagefaultsdstat -lvrn 5 # All in one tool sysctl -A # Kernel  netstat -punta / tcpdumpiftopsar , sar -q , sar -B , sar -b # historysar  -f /var/log/sa/ strace

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Profiling ToolsFio #Disk BenchmarkingSysbench # CPU Benchmarkingjstat/jmap for thread / heap dumpsOracle Java Mission ControlEclipse MAT / IBM MatJVisual VM with Visual GC jvmtop SJK - Java swiss knife - ttop, gc, stcap

Thank You!