Learn how to analyze Garbage Collection logs using HP Jmeter tool

1. HP Jmeter – GC analysis
Tutorial
Ram Lakshmanan
www.linkedin.com/in/ramlakshman/

2. Agenda
• Overview
• Key Visualizers
• Cool Tools

3. Overview
• HP Jmeter powerful tool for
• Garbage Collection Log file analysis
• Heap Dump analysis
• CPU Profiling
• Presentation focuses on Garbage Collection Log File analysis
• Download Location -
https://h20392.www2.hp.com/portal/swdepot/displayProductInfo.do
?productNumber=HPJMETER

4. Agenda
• Overview
• Key Visualizers
• Cool Tools

5. How to Open GC Log File?
Launch: <Jmeter-dir>/bin/hpjmeter.bat
Open GC File: Go to “File” menu > “Open File”

6. Having trouble in opening GC File?
• Check out – option #2 in http://tier1app.com/2013/06/14/gc-graph-from-
gc-logs/

7. Shows Summary of the Heap & it’s
statistics
Old Generation space
Perm Generation space
Total space
Usage during peak time in each generation
Too many occurrences of
Full GC is a indication of a
problem
Useful metric. Can be compared
with older version of code base
(Time spent in GC / Total Time
JVM is running). 67% is very
High percentage
Summary
Total # of GC Events = Scavenge GC
events + Old Full GC events + Other
full GC events

8. Shows Heap usage in the
eden space, old,
survivor, and permanent
generations after each
garbage collection.
Heap usage after GC
Note: After ‘Full GC’ ran
– memory reclaimed
significantly
Jmeter gets confused.
‘Old full’ and ‘other full’
are same i.e. ‘full’ GC.

9. Puzzle – Why Scavenge GC not reclaiming memory?
Memory is getting reclaimed. But
not pictured clearly in the graph.
Because of 2 reasons:
1. Objects are created in an
accelerated manner
2. Old Generation is not getting
reclaimed

10. Custom Views – Reclaimed Bytes
More Views available
Old GC is reclaiming more
bytes than new GC

11. Observations:
1. Repeated occurrences of
Full GC.
2. No Memory reclaimed
Clear Indication of
Memory Leak
Heap usage after GC – Sick JVM

12. Tab indicate how many times
‘Stop the world’ ran? When did it
Ran? How long
it took?
Indicates:
1. This GC took 2.75 secs to
Complete
2. It ran at 4:42pm
3. It was a “Full GC”
Indicates:
1. This GC took 0.2 secs to
Complete
2. It ran at 4:39:30pm
3. It was a “scavenge GC”
Duration – Stop the World

13. Agenda
• Overview
• Key Visualizers
• Cool Tools

14. Comparative Analysis
• Helpful tool to compare between GC log files.
• Use cases:
• Old code base GC Log vs New code base GC Log
• One application GC Log vs Another application GC Log

15. How to compare 2 GC logs?
1. Open both GC Log files
2. Click on ‘File’ > ‘Compare’ Menu
3. Click on ‘Compare’ button

16. Comparative Analysis
All comparative visualizers
Old Release code base heap usage
New Release code base heap usage

17. Zoom-in/Zoom-out
Zoom-out: click on this icon
Zoom-in: Interested to look certain data
points in detail:
- Click & drag

18. Helpful ‘Help’ Menu
• Go to any one of the View and click
on ‘Help’ Menu drop down. It will
take you to the appropriate Help
section.
• It has precise information

19. Thank you!
• Visit http://www.tier1app.com for further details on JVM, Memory,
GC