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Buffer Pool

Buffer Pool

The Buffer Pool page shows the memory samples stored for the direct and memory buffer of your JVM. In the top right of the page next to the Set Home Page you can switch graphs by clicking the Direct drop down button to view other the Mapped Buffer Pool graph. This works both ways.

Below is a sample image of the Buffer Pool Graph, which is currently set to Direct.

Several time spans are available, with differing resolutions. These will be filled as data points that are collected by FusionReactor.

Each time varying graphs shows two independent values overlaid: 

  • [SPACE NAME] Capacity
    • This is the current allocated memory for the specified buffer pool
  • [SPACE NAME] Memory Used
    • This is the currently used memory for the specified buffer pool

Direct Buffer Pool

Direct buffer is a chunk of memory typically used to interface Java to the OS I/O subsystems, from which Java can read directly. Java will grow this pool as required so the direct capacity is all buffer memory allocated so far.

Mapped Buffer Pool

The mapped buffer pool is all the memory used by Java for its FileChannel instances.
Buffer pool space is outside the garbage collector-managed memory.

You're able to deselect and reselect each independent values by simply clicking on their respective names. When a value is deselected (greyed out) then that value will no longer be displayed on the activity graph.


Placing your mouse pointer on a data point within the graph displays a tool-tip with details about that sample.

When browsing the 1 Hour, 1 Day, and 1 Week activity graphs you are able to select time frames by using the slider under the graph to pinpoint specific days, times and spikes in your memory. 

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