- System requirements
- Profiler architecture
- Running the profiler
- Profiler activation
- Start profiling
- Solving performance problems
- CPU profiling
- Threads
- Deadlock detector
- Memory profiling
- Memory telemetry
- Memory snapshot
- Object allocation recording
- Shallow and retained sizes
- Memory views
- Memory inspections
- Comparing memory snapshots
- Support of HPROF format snapshots
- Support of Java Flight Recorder (JFR)
- Support of Portable Heap Dumps (.phd)
- Values of primitive types
- Persistent object IDs
- Useful actions
- Set description language
- Garbage collection
- Monitor profiling
- Exception profiling
- Probes: monitor events of various kinds
- Performance Charts
- Inspections: automatic recognition of typical problems
- Automatically trigger actions on event
- Summary, snapshot annotation, automatic deobfuscation
- Time measurement (CPU time, wall time)
- Filters
- Snapshot directory customization
- Export of profiling results to HTML, CSV, XML, plain text
- Profiler Java API
- Profiler HTTP API
- Command line tool to control profiling
- Settings
- FAQ: How to profile in my scenario?
Comparing memory snapshots
This feature lets you compare any two memory snapshots.
To locate memory leaks, consider using the object generations feature.
To compare snapshots:
- Open both snapshots.
- Select one of them.
- Use File | Compare Snapshot with... (also available from the popup menu) and select the snapshot to compare with.
When comparing memory snapshots, there is an option to choose objects of which reachability scopes to be included to the comparison results:
The Comparison tab with memory views Classes and Classes and packages will open. The views have 2 columns: Objects (+/-) and Size (+/-). These display the differences in object counts and sizes. Positive values mean that Snapshot 2 (the later memory state) has more objects and/or its objects have the bigger total size.
100% of size corresponds to the total size of all objects in the old snapshot. Likewise, 100% of count corresponds to the object count in the old snapshot.
Please note that memory snapshot comparison provides only object count and size difference, it cannot tell which particular objects have gone or have been created between the snapshots being compared. This is because an object in the JVM heap does not essentially have a persistent ID. An object identifier is valid in particular snapshot only, it is in fact the object's physical address which may alter when the garbage collector compacts the heap or moves objects between heap generations. To address this limitation and enable object identification, YourKit profiler offers the object generations feature whose implementation involves object tagging with the help of the JVMTI API.