Page History

...

At startup, each Geode server with off-heap memory configured creates several off-heap fragments (each with a maximum of 2GB of size) so that any request to allocate an object could get a piece of any of the available fragments to store the object.
A list of tiny and huge memory chunks is also be maintained by Geode so that off-heap memory freed when deleting an off-heap object will be put in one of these two lists (depending on the amount of allocated memory) for further allocation requests of objects of the same size.

...

These stats would be available via JMX and gfsh.

These stats could be described as follows in the Geode documentation:

• largestFragment: Largest off-heap memory fragment that can be used to allocate an object. When an object is allocated from a fragment, the size of the fragment is decreased with the size of the object plus some heading and possibly some alignment bytes.
• freedChunks: Number of off-heap memory chunks that have been freed since the last defragmentation and that are not currently being used to store an object in the off-heap memory space.
  There are two types of chunks depending on the size of them: tiny if the size is lower than OFF_HEAP_ALIGNMENT* OFF_HEAP_FREE_LIST_COUNT (default = 512K) and huge if the size is greater.
  These chunks can also be used to allocate objects in the off-heap but the size of the freedChunk must comply with some conditions with respect to the object to be allocated. In order to allocate an object of tiny size between X and X-OFF_HEAP_ALIGMENT-1, a tinty freedChunk of size X must be found. In order to allocate an object of huge size between X and X-256-1, a huge freedChunk of size X must be found.

Other information that could be added to the off-heap documentation could be:

• When an off-heap object is freed, a freedChunk entry is created in either the tiny or the huge list depending on the freed memory.
• When defragmentation is run, Geode takes all freedChunks and remains of fragments and creates a new set of fragments by concatenating adjacent freedChunks and fragments.

Changes and Additions to Public Interfaces

...