Maximize Java Performance by using YOURKIT with uPortal development

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Maximize Java Performance by using YOURKIT with
uPortal development

• Faizan Ahmed Sr. Application Developer

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Overview

• Why memory related issues are problem?
• Introduction to YourKit.
• Some terms
• What is Java Memory Leak?
• Find and resolve memory leak (demo)
• Some code tips.

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Why memory related issues can be performance
problem?

• Memory-related issues affect execution speed and
  reliability of application.

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Getting started with YourKit

• Download and extract the zip file.
• Set PATH to dll
• ltYJP Homegt\bin\win32
• Check installation
• java -Xrunyjpagenthelp
• IDE configuration
• Plug-in installation
• Enable action group profile
• Windows customize perspective commands
• Agent configuration
• -agentlibyjpagent

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Snapshots

• YourKit investigative model is based upon
  snapshots which capture the state of the
  application at specific points in time.

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Dynamic Nature of a RootSet

• Root Set is a set of foundational object
  references within your application
• public class uPortal
• private static uPortal portal null
• public static void main(String args)
• portal new uPortal()
• portal.method1()

Root Set uPortal portal String args
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Dynamic Nature of a RootSet

• Private void method1
• FooObject fooObject new FooObject()
• ..

Root Set uPortal portal String args FooObject
fooObject
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Dynamic Nature of a RootSet

• public class uPortal
• private static uPortal portal null
• public static void main(String args)
• portal new uPortal()
• portal.method1()
• .

Root Set uPortal portal String args
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What is Memory leak in Java?

• Occurs when objects that have outlived their
  usefulness to the application remain within the
  heap through successive garbage collections

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What is a memory leak in Java?

• We can extend the set of object states to three
• Allocated
• Exists within the JVMs heap
• Reachable
• A path exists (directly or indirectly) from a
  member of the root set, through a sequence of
  references to that object.
• Live
• From the intent of the application design the
  program will use the object.

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What is memory leak in java?
Handled by JVM
Allocated
Reachable
Live
Java Memory leak
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What are loitered Objects?

• Loitered objects are reachable, but they are not
  live.

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Most common memory leak causes

• Failure to remove Stale Object References from
  Data Structures.
• Lingering Transitional references.
• A reference to a short-term object is used
  transiently by a long-term object but the
  long-term object does not clear the reference
  when its done with it.

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Preparing for your investigation

• Have a firm conceptual grasp of the architecture
  of the application you are about to analyze.
• An attitude that you can find, and resolve, the
  underlying problem.

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How to find leaked Objects?

• By Comparing snapshots.

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How to find leaked Objects?

• More Disciplined approach.
• Establish a hypothesis (around the expected leak
  area) (What you expect to see).
• Design and run an experiment to prove your
  hypothesis (a use case).
• Compare the experimental results against your
  hypothesis.
• Resolve the differences. (if any)

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Loitering Objects Recap

• Objects that remain within the heap past their
  useful life to the application.
• To eliminate loitering objects from your
  application, you must first
• Identify which objects (if any) are loitering
  within your application.
• Determine why those objects remain reachable
  beyond their designed lifetime.

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Some Tips

• Reference variable scope
• Dont be concerned about assignments to
  method-based reference variables within methods
  of short execution time.
• Be attentive of assignments to class-based and
  object-based reference variables, and
  method-based reference variables within methods
  of long execution time.

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Some Tips

• As a general rule do not use finalizer.
• Where appropriate to your design, use the method
  attributes
• static
• final
• private

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Some Tips (Continued)

• Try to keep critical methods to a few statements
  in length, and declare them static, final or
  private.
• In critical loops, avoid method calls within the
  loop termination test..
• Example on next page

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Some Tips (Continued)

• Replace
• for (int i0 i lt collection.size() i)
• .
• With
• for(int i0, ncollection.size() iltn i)
• ---

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Some Tips (Continued)

• If you cache some objects you better have a
  working caching strategy and remove objects
  from cache at some point.
• No user session really means 0 user session in
  the system.

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Questions Comments !