21.6.15.26 The ndbinfo memoryusage Table (original) (raw)

21.6.15.26 The ndbinfo memoryusage Table

Querying this table provides information similar to that provided by the ALL REPORT MemoryUsage command in the ndb_mgm client, or logged by ALL DUMP 1000.

The memoryusage table contains the following columns:

• node_id
  The node ID of this data node.
• memory_type
  One of Data memory, Index memory, or Long message buffer.
• used
  Number of bytes currently used for data memory or index memory by this data node.
• used_pages
  Number of pages currently used for data memory or index memory by this data node; see text.
• total
  Total number of bytes of data memory or index memory available for this data node; see text.
• total_pages
  Total number of memory pages available for data memory or index memory on this data node; see text.

Notes

The total column represents the total amount of memory in bytes available for the given resource (data memory or index memory) on a particular data node. This number should be approximately equal to the setting of the corresponding configuration parameter in the config.ini file.

Suppose that the cluster has 2 data nodes having node IDs5 and 6, and theconfig.ini file contains the following:

[ndbd default]
DataMemory = 1G
IndexMemory = 1G

Suppose also that the value of theLongMessageBuffer configuration parameter is allowed to assume its default (64 MB).

The following query shows approximately the same values:

mysql> SELECT node_id, memory_type, total
     > FROM ndbinfo.memoryusage;
+---------+---------------------+------------+
| node_id | memory_type         | total      |
+---------+---------------------+------------+
|       5 | Data memory         | 1073741824 |
|       5 | Index memory        | 1074003968 |
|       5 | Long message buffer |   67108864 |
|       6 | Data memory         | 1073741824 |
|       6 | Index memory        | 1074003968 |
|       6 | Long message buffer |   67108864 |
+---------+---------------------+------------+
6 rows in set (0.00 sec)

In this case, the total column values for index memory are slightly higher than the value set ofIndexMemory due to internal rounding.

For the used_pages andtotal_pages columns, resources are measured in pages, which are 32K in size forDataMemory and 8K forIndexMemory. For long message buffer memory, the page size is 256 bytes.