eG Help

The buffer pool is an area in main memory where InnoDB caches table and index data as it is accessed.The buffer pool permits frequently used data to be accessed directly from memory, which speeds up processing. On dedicated servers, up to 80% of physical memory is often assigned to the buffer pool. For efficiency of high-volume read operations, the buffer pool is divided into pages that can potentially hold multiple rows. For efficiency of cache management, the buffer pool is implemented as a linked list of pages; data that is rarely used is aged out of the cache using a variation of the least recently used (LRU) algorithm.

If the size of the buffer pool is inadequate or if the buffer pool is poorly sized, then, more often than not, the requests may not be serviced by the buffer pool. Similarly if too many pages in the buffer pool are held for administrative purpose or are being held for read/write operations, then, InnoDB may not be able to cache the tables and data in the buffer pool. If the required data is not available in the buffer pool, requests may have to be serviced directly from the disk Which may cause severe overheads. To avoid such overheads, it is necessary for the administrators to constantly keep a vigil on the sizing of the buffer pool and the memory allocated to the buffer pool. The MySQLCluInEngTest helps administrators in this regard!

This test monitors the InnoDB buffer pool on each node of the target MySQL Cluster and reports the amount of memory allocated to the buffer pool and the amount of memory utilized by the buffer pool. The statistics reported by this test help administrators analyze the usage of the buffer pool, and provides them with useful pointers to fine-tune the configuration of the buffer pool.

Outputs of the test :One set of results for each node on the target MySQL Cluster database server being monitored

Measurement	Description	Measurement Unit	Interpretation
totalMemoryAllocated	Indicates the total amount of memory allocated to the buffer pool of this node.	MB
freeMemoryTotalSize	Indicates the amount of memory available for use in the pages allocated to the buffer pool of this node.	MB	A high value is desired for this measure.
usedMemorySize	Indicates the amount of memory that is already utilized in the pages allocated to the buffer pool of this node.	MB	A value close to Total memory allocated measure is an indication that the buffer pool is currently running out of memory.
usedMemoryPercentage	Indicates the percentage of memory utilized by the pages allocated to the buffer pool of this node.	Percent	A low value is desired for this measure.A value close to 100 indicates that the buffer pool is running out of memory resources. The value of this measure is calculated as follows: (Used memory / Total memory allocated) * 100
addMemoryAllocated	Indicates the amount of memory that is additionally allocated to the buffer pool of this node.	MB	MySQL server stores details such as metadata accessed by the users, internal information structure etc. in the additional memory allocated to the buffer pool.
dicMemAllocated	Indicates the amount of memory allocated for the data dictionary of the InnoDB storage engine in this node.	MB
totalPageSizeInMemory	Indicates the total size of the buffer pool of this node, in pages.	MB	The value of this measure is a sum of Data page size, Dirty page size and Misc page size measures.
dataPageSizeInMemory	Indicates the size of the pages containing data in the buffer pool.	MB
dirtyPageSizeInMemory	Indicates the amount of bytes held in the dirty pages available in the buffer pool of this node.	MB
miscPageSizeInMemory	Indicates the size of the pages that have been allocated for administrative overhead, such as row locks or the adaptive hash index.	MB
latchedPagesInMemeory	Indicates the number of latched pages in the buffer pool of this node.	Number	These are pages currently being read or written, or that cannot be flushed or removed for some other reason.
flushedPageSizeInMemory	Indicates the size of pages that were flushed from the buffer pool of this node.	MB