MySQL also allocates memory for temporary tables unless it becomes too large (determined by tmp_table_size and max_heap_table_size). MyISAM also maintains one extra row buffer for internal use. MyISAM also allocates buffer for every concurrent threads which contains a table structure, column structures for each column, and a buffer of size 3 * N are allocated (where N is the maximum row length, not counting BLOB columns). While for MyISAM, you have to deal with key_buffer_size to handle the amount of memory that the key buffer will handle. It’s desirable if you have large memory and are expecting to handle big transactions by setting innodb_buffer_pool_instances to improve concurrency by dividing the buffer pool into multiple buffer pool instances. For example, the most common variables every DBA will set in InnoDB are variables innodb_buffer_pool_size and innodb_buffer_pool_instances which are both related to buffer pool memory allocation that holds cached data for InnoDB tables. When a mysqld instance spawns within the host system, MySQL allocates buffers and caches to improve performance of database operations based on the set values set on a specific configuration.
In most cases, the memory-specific variables set for a configuration are targeted on a storage-based specific configuration such as MyISAM or InnoDB. Query joins, query caches, sorting, table cache, table definitions do require memory in MySQL but these are attributed with system variables that you can configure and set. In that case, the memory remains allocated. When a thread is no longer needed, the memory allocated to it is released and returned to the system unless the thread goes back into the thread cache. Variables like thread_stack (stack for threads), net_buffer_length (for connection buffer and result buffer), or with max_allowed_packet where connection and result will dynamically enlarge up to this value when needed, are variables that do affect memory utilization. Each thread in MySQL demands memory which is used to manage client connections, and these threads share the same base memory. Memory plays a significant resource for speed and efficiency when handling concurrent transactions and running big queries. Memory Allocation in MySQLīefore we delve into the specific subject title, I’ll just give a short information about how MySQL uses memory. Let’s cover these topics and show the things you can check in MySQL to determine traces of high memory utilization. But how can you determine if the MySQL utilization is optimized? Is it reasonable to have high memory utilization or does it require fine tuning? What if I come up against a memory leak?
One of the key factors of a performant MySQL database server is having good memory allocation and utilization, especially when running it in a production environment.
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