Page History

Aprof is a Java memory allocation profiler with very low performance impact on the profiled application that can be used (and is used) on highly-loaded server-side applications in production environment. It acts as an agent which transforms class bytecode by inserting counter increments wherever memory allocation is done and tracks a precise size of allocated objects in bytes. It also keeps limited information about allocation context to aid to finding the memory allocation bottlenecks. 

Using aprof

Download the latest version of aprof distribution, unzip, copy "aprof.jar" to your application's directory and run application with an additional JVM argument:

...

Do not rename agent file "aprof.jar", because it is configured by its name in manifest and will not work when renamed. 

Features overview

• Fast (can be used and is designed to be used in production) 
• Provides detailed information (can be used to identify problematic pieces of code)
• Configurable level of detail (as a compromise between speed and level of detail)
  

• Open Source (see, learn, improve)

...

• Does not take into account the fact, that some memory allocation are removed by modern HotSpot VM, however it does not prevents HotSpot from allocating objects on stack.
• Does not work on some releases of 1.6 (1.6.0_21 crashes with FATAL ERROR), but otherwise works in Java 1.5 to Java 1.7.
• Does not fully analyze inheritance hierarchy when tracking configured method invocations. It does not intercept locations of invocations of tracked methods that are performed via a sub-type that inherits the tracked method, It does misleadingly report invocation locations of a non-tracked method that happen to go via super-type that declares a tracked method for some other implementation of this type where this method is tracked. 

Origin and Goals

Java VM has an option -Xaprof printing how many instances of classes were allocated during lifetime of the application and how much memory they occupied in total and per instance. The option has no performance impact due to the fact that counting takes place during garbage collection. The only drawbacks are occasional overflows of counters and the absence of any information on locations where the object allocations take place.

Aprof aims to overcome drawbacks of Java VM option -Xaprof by:

• collecting information on locations where the object allocations take place. 
• providing an accurate profiling results.
• having very low performance impact (to be safely used in production environments).

When to use Aprof

Aprof should be used when the application spends a lot of time in garbage collection. Due to the specifics of Java VM, objects are allocated so fast that CPU profilers are unable to pinpoint the allocation hotspot. The only way is to use memory allocation profilers.

...

As a result, memory allocation profilers leave us with both inaccurate profiling results and an impact on the profiled application.

Aprof gets Aprof gets accurate profiling results and finds locations of object allocations at the same time being garbage-free and having very low performance impact.