MariaDB / MySQL InnoDB Memory Calculator

How to estimate InnoDB memory accurately

InnoDB memory is more than innodb_buffer_pool_size. The calculator counts the buffer pool, an adjustable allowance for its control structures, the global innodb_log_buffer_size, and additional InnoDB allocations you provide. MySQL documents roughly 10% extra space for buffer pool structures; the actual allowance depends on the build and workload, especially in MariaDB. Use the effective running value, which may differ from the requested configuration after buffer pool size rounding.

The data dictionary, adaptive hash index, locks, transaction structures and compression can add memory. Measure these where possible and enter only allocations not already included in the pool or its allowance. Redo log capacity, redo files and undo tablespace sizes are disk capacity: do not add their file sizes as RAM. An InnoDB subtotal excludes other engines, Performance Schema, connection/query buffers and the operating system.

Collect your running settings

Run these read-only statements on the target server. Unsupported variables are omitted by SHOW ... WHERE. Threads_running includes the collecting query and is a snapshot; use representative concurrency and recorded peaks. Max_used_connections is a connection peak, not an active-query peak. Check session values from application connections too: the current session does not describe every session.

SELECT VERSION();
SHOW GLOBAL VARIABLES WHERE Variable_name IN (
  'innodb_buffer_pool_size', 'innodb_log_buffer_size', 'innodb_page_size',
  'key_buffer_size', 'aria_pagecache_buffer_size', 'query_cache_size',
  'max_connections', 'thread_handling', 'thread_stack', 'net_buffer_length',
  'max_digest_length', 'max_allowed_packet', 'sort_buffer_size',
  'join_buffer_size', 'read_buffer_size', 'read_rnd_buffer_size',
  'tmp_table_size', 'max_heap_table_size', 'internal_tmp_mem_storage_engine',
  'temptable_max_ram', 'temptable_max_mmap', 'temptable_use_mmap'
);
SHOW GLOBAL STATUS WHERE Variable_name IN (
  'Threads_connected', 'Threads_running', 'Max_used_connections',
  'Created_tmp_tables', 'Created_tmp_disk_tables',
  'Innodb_buffer_pool_pages_total', 'Innodb_buffer_pool_pages_data',
  'Innodb_buffer_pool_pages_free'
);
SHOW SESSION VARIABLES WHERE Variable_name IN (
  'sort_buffer_size', 'join_buffer_size', 'read_buffer_size',
  'read_rnd_buffer_size', 'tmp_table_size', 'max_heap_table_size',
  'internal_tmp_mem_storage_engine', 'max_allowed_packet'
);
SHOW ENGINE INNODB STATUS;

Measure InnoDB and process memory

If your version exposes this Performance Schema memory table and InnoDB instruments are enabled, inspect the current allocations below. Instrumentation coverage differs by version and enabling counters later does not reconstruct every earlier allocation. Missing rows or zeros do not prove zero memory use. Do not sum per-instrument high-water marks to infer a simultaneous peak. Enter the current sum in the optional measured InnoDB field; it stays separate from the model.

SELECT EVENT_NAME,
       ROUND(CURRENT_NUMBER_OF_BYTES_USED / 1048576, 2) AS current_mib,
       ROUND(HIGH_NUMBER_OF_BYTES_USED / 1048576, 2) AS high_mib
FROM performance_schema.memory_summary_global_by_event_name
WHERE EVENT_NAME LIKE 'memory/innodb/%'
ORDER BY CURRENT_NUMBER_OF_BYTES_USED DESC;

SELECT ROUND(SUM(CURRENT_NUMBER_OF_BYTES_USED) / 1048576, 2)
       AS instrumented_innodb_mib
FROM performance_schema.memory_summary_global_by_event_name
WHERE EVENT_NAME LIKE 'memory/innodb/%';

On Linux, RSS below is in KiB; use a K suffix or divide by 1024 for MiB. RSS covers the process, not only InnoDB. Account for cgroup limits, OS page cache, allocator retention and other services when interpreting it.

ps -C mariadbd,mysqld -o pid=,rss=,comm=

Temporary table rules and practical limits

For MariaDB and MySQL using MEMORY for internal temporary tables, the smaller of tmp_table_size and max_heap_table_size limits each table. Multiple tables and join buffers can coexist in one query. The model applies your chosen multiplicities to active queries; it does not allocate every query buffer to every idle connection.

For MySQL TempTable, temptable_max_ram is shared across sessions. From 8.0.28, tmp_table_size also limits each individual table. The earlier TempTable profile uses the shared limit without that per-table cap. Thread-local blocks are outside the shared RAM limit; the model conservatively allows one for every connected session because it may remain until thread exit. A block can exceed the illustrated 1 MiB. Memory-mapped temporary files can contribute resident pages and require additional headroom; their file limit is not equivalent to allocated RAM.

The stress scenario makes all max_connections connections active with the same query shape. It is not a guaranteed upper bound. Add allowances for user MEMORY tables, packet growth, SQL/BLOB data, binary log caches, replication, prepared statements, thread caches and any unmodeled allocation. Validate the model against measured process peaks under representative load. Neither this estimate nor a tuning target enforces a memory cap.

Sources and verification

Checked on 13 October 2026. This page uses original explanations informed by Releem and the server manuals. Releem’s temporary-table example lists 200 connections and 32 MiB limits, then multiplies by 16 MB; the consistent one-table-per-connection result is 6400 MiB = 6.25 GiB. The engine-specific manuals take precedence over a generic formula.

• Releem — memory calculator
• Releem — MySQL memory usage
• Releem — tmp_table_size
• MariaDB — memory allocation
• MySQL — memory use
• MySQL — temporary tables
• MySQL — InnoDB parameters