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InnoDB memory usage discrepancies
Posted by: Ankur Shukla
Date: December 27, 2022 05:26AM

MySQL v8.0.23

I am trying to understand memory used by mysql server, with InnoDb engine. This is a dedicated server for mysql only. I pulled memory stats using free, top, and from within mysql. Considering major memory for buffer pool and connections, there is a different of ~20GB in output of top/free and mysql internal calculations.

free -mh
total used free shared buff/cache available
Mem: 119G 104G 876M 908K 14G 13G
Swap: 0B 0B 0B

top -o %MEM
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
26502 mysql 20 0 0.103t 0.102t 12120 S 113.3 86.7 265894:41 mysqld
129344 root 19 -1 352404 138448 133868 S 0.0 0.1 9:12.45 systemd-journal

mysql> select @@innodb_buffer_pool_size;
+---------------------------+
| @@innodb_buffer_pool_size |
+---------------------------+
| 83751862272 |
+---------------------------+


mysql> show global status like 'max_used_connections';
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| Max_used_connections | 423 |
+----------------------+-------+

SELECT ( @@key_buffer_size + @@innodb_buffer_pool_size + 423 * (@@read_buffer_size + @@read_rnd_buffer_size + @@sort_buffer_size + @@join_buffer_size + @@tmp_table_size )) / (1024*1024*1024)
AS MAX_MEMORY_GB;
+---------------+
| MAX_MEMORY_GB |
+---------------+
| 86.5277 |
+---------------+

mysql> show variables like '%innodb%';
+------------------------------------------+------------------------+
| Variable_name | Value |
+------------------------------------------+------------------------+
| innodb_adaptive_flushing | ON |
| innodb_adaptive_flushing_lwm | 10 |
| innodb_adaptive_hash_index | ON |
| innodb_adaptive_hash_index_parts | 8 |
| innodb_adaptive_max_sleep_delay | 150000 |
| innodb_api_bk_commit_interval | 5 |
| innodb_api_disable_rowlock | OFF |
| innodb_api_enable_binlog | OFF |
| innodb_api_enable_mdl | OFF |
| innodb_api_trx_level | 0 |
| innodb_autoextend_increment | 64 |
| innodb_autoinc_lock_mode | 2 |
| innodb_buffer_pool_chunk_size | 134217728 |
| innodb_buffer_pool_dump_at_shutdown | ON |
| innodb_buffer_pool_dump_now | OFF |
| innodb_buffer_pool_dump_pct | 25 |
| innodb_buffer_pool_filename | ib_buffer_pool |
| innodb_buffer_pool_in_core_file | ON |
| innodb_buffer_pool_instances | 8 |
| innodb_buffer_pool_load_abort | OFF |
| innodb_buffer_pool_load_at_startup | ON |
| innodb_buffer_pool_load_now | OFF |
| innodb_buffer_pool_size | 83751862272 |
| innodb_change_buffer_max_size | 25 |
| innodb_change_buffering | all |
| innodb_checksum_algorithm | crc32 |
| innodb_cmp_per_index_enabled | OFF |
| innodb_commit_concurrency | 0 |
| innodb_compression_failure_threshold_pct | 5 |
| innodb_compression_level | 6 |
| innodb_compression_pad_pct_max | 50 |
| innodb_concurrency_tickets | 5000 |
| innodb_data_file_path | ibdata1:12M:autoextend |
| innodb_data_home_dir | |
| innodb_deadlock_detect | ON |
| innodb_dedicated_server | OFF |
| innodb_default_row_format | dynamic |
| innodb_directories | |
| innodb_disable_sort_file_cache | OFF |
| innodb_doublewrite | ON |
| innodb_doublewrite_batch_size | 0 |
| innodb_doublewrite_dir | |
| innodb_doublewrite_files | 2 |
| innodb_doublewrite_pages | 32 |
| innodb_extend_and_initialize | ON |
| innodb_fast_shutdown | 1 |
| innodb_file_per_table | ON |
| innodb_fill_factor | 100 |
| innodb_flush_log_at_timeout | 1 |
| innodb_flush_log_at_trx_commit | 0 |
| innodb_flush_method | fsync |
| innodb_flush_neighbors | 0 |
| innodb_flush_sync | ON |
| innodb_flushing_avg_loops | 30 |
| innodb_force_load_corrupted | OFF |
| innodb_force_recovery | 0 |
| innodb_fsync_threshold | 0 |
| innodb_ft_aux_table | |
| innodb_ft_cache_size | 8000000 |
| innodb_ft_enable_diag_print | OFF |
| innodb_ft_enable_stopword | ON |
| innodb_ft_max_token_size | 84 |
| innodb_ft_min_token_size | 3 |
| innodb_ft_num_word_optimize | 2000 |
| innodb_ft_result_cache_limit | 2000000000 |
| innodb_ft_server_stopword_table | |
| innodb_ft_sort_pll_degree | 2 |
| innodb_ft_total_cache_size | 640000000 |
| innodb_ft_user_stopword_table | |
| innodb_idle_flush_pct | 100 |
| innodb_io_capacity | 200 |
| innodb_io_capacity_max | 2000 |
| innodb_lock_wait_timeout | 50 |
| innodb_log_buffer_size | 33554432 |
| innodb_log_checksums | ON |
| innodb_log_compressed_pages | ON |
| innodb_log_file_size | 536870912 |
| innodb_log_files_in_group | 2 |
| innodb_log_group_home_dir | ./ |
| innodb_log_spin_cpu_abs_lwm | 80 |
| innodb_log_spin_cpu_pct_hwm | 50 |
| innodb_log_wait_for_flush_spin_hwm | 400 |
| innodb_log_write_ahead_size | 8192 |
| innodb_log_writer_threads | ON |
| innodb_lru_scan_depth | 1024 |
| innodb_max_dirty_pages_pct | 90.000000 |
| innodb_max_dirty_pages_pct_lwm | 10.000000 |
| innodb_max_purge_lag | 0 |
| innodb_max_purge_lag_delay | 0 |
| innodb_max_undo_log_size | 1073741824 |
| innodb_monitor_disable | |
| innodb_monitor_enable | |
| innodb_monitor_reset | |
| innodb_monitor_reset_all | |
| innodb_numa_interleave | OFF |
| innodb_old_blocks_pct | 37 |
| innodb_old_blocks_time | 1000 |
| innodb_online_alter_log_max_size | 134217728 |
| innodb_open_files | 4000 |
| innodb_optimize_fulltext_only | OFF |
| innodb_page_cleaners | 4 |
| innodb_page_size | 16384 |
| innodb_parallel_read_threads | 4 |
| innodb_print_all_deadlocks | OFF |
| innodb_print_ddl_logs | OFF |
| innodb_purge_batch_size | 300 |
| innodb_purge_rseg_truncate_frequency | 128 |
| innodb_purge_threads | 4 |
| innodb_random_read_ahead | OFF |
| innodb_read_ahead_threshold | 56 |
| innodb_read_io_threads | 32 |
| innodb_read_only | OFF |
| innodb_redo_log_archive_dirs | |
| innodb_redo_log_encrypt | OFF |
| innodb_replication_delay | 0 |
| innodb_rollback_on_timeout | OFF |
| innodb_rollback_segments | 128 |
| innodb_sort_buffer_size | 1048576 |
| innodb_spin_wait_delay | 6 |
| innodb_spin_wait_pause_multiplier | 50 |
| innodb_stats_auto_recalc | ON |
| innodb_stats_include_delete_marked | OFF |
| innodb_stats_method | nulls_equal |
| innodb_stats_on_metadata | OFF |
| innodb_stats_persistent | ON |
| innodb_stats_persistent_sample_pages | 20 |
| innodb_stats_transient_sample_pages | 8 |
| innodb_status_output | OFF |
| innodb_status_output_locks | OFF |
| innodb_strict_mode | ON |
| innodb_sync_array_size | 1 |
| innodb_sync_spin_loops | 30 |
| innodb_table_locks | ON |
| innodb_temp_data_file_path | ibtmp1:12M:autoextend |
| innodb_temp_tablespaces_dir | ./#innodb_temp/ |
| innodb_thread_concurrency | 0 |
| innodb_thread_sleep_delay | 10000 |
| innodb_tmpdir | |
| innodb_undo_directory | ./ |
| innodb_undo_log_encrypt | OFF |
| innodb_undo_log_truncate | ON |
| innodb_undo_tablespaces | 2 |
| innodb_use_native_aio | ON |
| innodb_validate_tablespace_paths | ON |
| innodb_version | 8.0.23 |
| innodb_write_io_threads | 32 |
+------------------------------------------+------------------------+
146 rows in set (0.00 sec)


The used memory is ~104GB with no other process using significant RAM. What else could be contributing to mysql memory usage?

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InnoDB memory usage discrepancies
December 27, 2022 05:26AM


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