Application Profiling for Memory and Performance

Application Profiling
for
Memory & Performance
Srinath Perera Pradeep Fernando Dinuka Malalanayke
WSO2 Inc WSO2 Inc WSO2 Inc

Understanding Server Performance

When Concurrency Increases?

• Throughput increases, but where will it stop?
• When there are contention for the server
• Contention for what?
o CPU
o Memory
o Disk - I/O
o Network -I/O
• If your server running on full capacity, there should be at
least one resource under contention.

How to measure Contention?

• CPU - CPU or load average
• Memory - GC logs, monitor memory, sometime swapping
• Disk I/O - IOPS per seconds, load average
• Network I/O - network utilization, load average
• What is load average? length of processor queue of the OS
• How much load average is too much?
o Load average = number of cores (machine is fully used)
o Load average = 2* number of cores (machine is loaded)

If you cannot find contention

• Either load is too small
• You have too much locks. Look for lock profile
• Server might be processing with too less threads (IO and
CPU thread switches)

Performance Tuning

• Increase throughput/ latency or both
• Know that latency vs. throughput is often a tradeoff
• Run the system and see how it does, make sure you are
putting in enough load
• Verify where is the bottleneck? is it CPU, memory, network,
or disk
• Start tuning

Tuning

• When you tune, bottlenecks will shift, you will have to shift
your focus
• Can you tune settings (Application, JVM, OS) to improve and
shift the bottleneck? play with parameters .. we call this
parameter sweep
• Then focus on the code, look for right profile
o CPU profile
o Memory/ Allocation profile
o Network profile
o IO profile
o Database profile

Programmer Nightmares

ClassCastException
Permgen Errors
DeadLocks
NullPointer
Unacceptable Latency
CPU spin OutofMemoryException
ArrayIndexOutOfBoundsException

[image] http://www1.free-clipart.net/gallery2/clipart/Holidays/Halloween/Ghost_-_Boo.jpg

Introducing: Profiling...

• Best thing would be to write bug free, high performant code
• Normally development happens in iterative manner - get
something to work and improve on that.
• Basic profiling can help you to eliminate most of the memory
and performance issues.

Right Tools...

• There are many commercial and open source tools
• We are going to use,
o Jprofiler by ejTechnologies
 CPU, Memory, Allocation, Network, DB
o Eclipse Memory Analyzer tool
 Find memory leaks
o Standard JDK tooling - Jconsole
 Basic stats

[image] http://writingsongs.com/pictures/toolbox.jpg

Environment Setup
With WSO2 Carbon

Setting up JProfiler

• Profiling modes local/remote
• Applying common filters for WSO2 products
• Different views..

JProfiler Contd.

CPU view
- Call trees, Hot spots
Memory view
- Allocation Hot spots, Recorded objects, Heap walker
VM telemetry view
- Memory, Threads status graphs
Probes
- JDBC , Sockets

JConsole

• Connect to the running instance local/remote
• Different memory banks
• Getting most out of Mbeans.
• Getting a memory dump and analyzing with Eclipse MAT.
• Remote JMX URL gets printed in the console during server
startup:

JMX Service URL : service:jmx:rmi://localhost:11111/jndi/rmi://localhost:9999/jmxrmi
username : admin password : admin

Memory Analyzer Tool

• Analyze heap dumps.
• Identifying OOM issues are trivial with basic leak report.

Usual Suspects

Some of the common issues...

Permgen Errors

• Permgen space relates to the 'Programme code' part, a.k.a -
Loaded classes.
• ClassLoader leaks
• Typically happens in Container environments
• Can uncover by doing deploy/redeploy cycles.
• If one of the application objects get referenced by an object,
outside the application, permgen error waiting to happen.

Permgen Errors

Container

URLClassLoader Application

Application Objects
Container provided
Objects

Memory Leaks - OOM

• Languages like C, gave the control of memory to the
programmer.
• Java is a managed memory, language.
• Still the JVM can't free up the memory, if the application is
holding on to the objects.
• Unnecessary accumulation of objects,
o Object creation for each and every connection
o Slow output rate in the input/output system
o Collecting clusterwide messages without an upper bound.

DeadLocks

Resource A

Resource B

• Re-designing the lock acquiring sequence
• Using LockManagers that keeps track of lock acquisition

Liveness issues...

• Starvation - A thread can starve for CPU cycles, if it is
blocked by a lock-wait.
• Poor Responsiveness
• LiveLock scenarios

Programming Best Practices

• Think about memory aspects/ data retrieval process while
writing code.
• Optimize the critical Path (look at CPU profile).
• Make use of Standard libs as much as possible.
• Profile your apps before releasing them to production.

Identity Server - Losing weight

• Carbon server optimized to run in constrained memory
environment.
• No front end components - 'createWorker' ant task.
• Selective Admin service loading. -Doptimized=true
• Removed unwanted functionality based on the use-case,
(p2 - provisioning, etc)

Raspberry-Pi Clusters

• Application server
cluster running on R-
Pis.
• Powering the
WSO2Con 2013
mobile app
• 512MB of RAM and
ARM processor.

Demo

CPU spin and Memory leak scenario

Application Profiling for Memory and Performance

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