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Foglight 5.9.5 - Performance Tuning Field Guide

Overview Hardware and Operating System Tuning Management Server Tuning Java Virtual Machine Tuning Backend Database Tuning High Availability (HA) Tuning Agent Tuning Appendix: Performance Health Check Appendix: Analyzing a Support Bundle


This switch enables a concurrent low-pause garbage collector.

Enabled, since release 5.2.3.

Do not change this setting unless advised by Quest Support.

-Xmx and -Xms

These switches specify the maximum and initial size (respectively), in bytes, of the memory allocation pool (the heap). Each value must be a multiple of 1024 and greater than 512 MB. Append the letter m or M to indicate megabytes, or g or G to indicate gigabytes.




32-bit: 256m < 75% avail < 1024m

64-bit: 512m < 75% avail < 4096m*

Increasing memory can improve the server’s performance. You should run the server with the default settings first. Close monitoring of Server Load in the Performance Overview dashboard (Foglight|Diagnostic) will reveal any over-utilization or under-utilization of memory:


THEN increase the maximum heap size


THEN consider decreasing the heap size to a lower value between the highest minimum of the memory_usage plot and the totalMemory to reduce resource allocation

Check the overall memory allocation on the machine hosting Foglight.

- Hard page faults are giving away “over-allocation” (1 GB for the OS + 12 GB for the VM heap + 2 GB for the VM overhead + 1 GB for the Agent Manager and the agents + 2 GB for an embedded MySQL database is more than enough for a 16 GB setup).

When optimizing Agent Manager startup JVM parameters, the -Xms and -Xmx values do not have to be the same, because the memory usage pattern of the Agent Manager is quite different from that of the Management Server. For the Agent Manager, -Xms should be set to the lowest estimated value of the expected steady state of the Agent Manager when running all agent instances. This -Xms configuration is different from what is recommended for the Management Server.

-XX:NewSize, -XX:MaxNewSize, and -XX:NewRatio

These switches specify the (initial/maximum) size of the young object space where new objects are allocated. For the NewSize switches, append the letter m or M to indicate megabytes, or g or G to indicate gigabytes.



-XX:NewRatio=4 (1:4)



Foglight® receives and processes a lot of transient data that is best handled in the JVM’s new generation part of the heap. If you reserve a minimum size for this type of memory, that guarantees fast throughput with low memory management overhead. The result of a large young space size may be increased garbage collection pause times.

Unless specifically instructed to do so, you should not change this parameter.


This switch specifies the memory allocated to hold the reflective data (such as class objects and method objects) of the VM itself. These reflective objects are allocated directly into the permanent generation, which is sized independently from the other generations.



96m < -Xmx/4 < 512m*

Foglight is a dynamic application platform that loads and manages a lot of deployed dynamic components. The default value has been tested and utilized in the field.

Unless specifically instructed to do so, you should not change this parameter.

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