Mysql 每个线程内存，导致线程内存使用的变量？
Mysql per thread memory, variables that lead to thread memory usage?
我们最近在几台服务器上从 mysql 5.6 升级到 mysql 8.0，其中一台服务器很好，没有问题，但它
负载明显低于我们的其他服务器 运行 内存不足的服务器之一。
我们的服务器启动，然后获取 300 个连接，并使用 C3P0 池将它们保持打开到 mysql 服务器。
我们在 MySQL 5.6 上的 AWS 上 运行 这些服务器在 8GB RAM 上具有相同的覆盖参数，当我们升级到 MySQL 8.0.21 时，我们开始 运行 大约 1 天内存不足。我们将服务器增加到 32Gb 但没有更改参数。它已使用超过 15 GB，并且还在增加。
我们很确定它与每个连接线程内存有关，但不确定原因。从 MySQL 调谐器来看，控制每个线程内存的变量似乎是：
read_buffer_size 1048576
read_rnd_buffer_size 4194304
sort_buffer_size 1048576
thread_stack 262144
max_allowed_packet 4194304
join_buffer_size 262144
总共有 10.5 Mb。我在这里缺少变量吗？
查看 memory_by_thread_by_current_bytes 我们有超过 200Mb 的连接
服务器是 运行AWS RDS 上的 8.0.21
还有其他问题我应该 运行 弄清楚是什么占用了线程上的所有这些 ram？
通常 innodb 缓冲池是 4GB，但是当我们在 8GB 的机器上为了多一点空间时，我们把它降到了 3GB。
select * from sys.memory_by_thread_by_current_bytes;
thread_id `user` current_count_used current_allocated current_avg_alloc current_max_alloc total_allocated
315 cluster@10.0.13.68 1880 209.77 MiB 114.26 KiB 204.10 MiB 21.51 GiB
336 cluster@10.0.13.68 2288 207.75 MiB 92.98 KiB 204.10 MiB 23.38 GiB
358 cluster@10.0.13.68 1847 207.35 MiB 114.96 KiB 204.01 MiB 19.66 GiB
272 cluster@10.0.13.68 1347 205.59 MiB 156.29 KiB 204.77 MiB 24.91 GiB
328 cluster@10.0.13.68 1825 204.55 MiB 114.77 KiB 204.14 MiB 23.84 GiB
276 cluster@10.0.13.68 1486 204.08 MiB 140.63 KiB 201.70 MiB 21.31 GiB
313 cluster@10.0.13.68 975 203.05 MiB 213.26 KiB 203.56 MiB 19.70 GiB
258 cluster@10.0.13.68 1244 202.76 MiB 166.91 KiB 201.56 MiB 19.58 GiB
288 cluster@10.0.13.68 1431 201.49 MiB 144.19 KiB 201.48 MiB 19.39 GiB
248 cluster@10.0.13.68 1265 175.83 MiB 142.33 KiB 175.15 MiB 17.04 GiB
284 cluster@10.0.13.68 978 174.08 MiB 182.27 KiB 175.34 MiB 18.25 GiB
343 cluster@10.0.13.68 2038 143.98 MiB 72.34 KiB 139.14 MiB 16.84 GiB
329 cluster@10.0.13.68 1971 142.77 MiB 74.17 KiB 138.54 MiB 17.93 GiB
355 cluster@10.0.13.68 1646 141.74 MiB 88.18 KiB 136.37 MiB 15.04 GiB
327 cluster@10.0.13.68 1805 139.95 MiB 79.39 KiB 136.15 MiB 15.95 GiB
330 cluster@10.0.13.68 2001 139.72 MiB 71.50 KiB 136.08 MiB 14.69 GiB
351 cluster@10.0.13.68 2129 139.45 MiB 67.07 KiB 136.57 MiB 16.34 GiB
316 cluster@10.0.13.68 1598 139.01 MiB 89.08 KiB 136.46 MiB 17.56 GiB
293 cluster@10.0.13.68 1238 138.29 MiB 114.39 KiB 136.24 MiB 15.53 GiB
345 cluster@10.0.13.68 1196 137.95 MiB 118.11 KiB 137.40 MiB 15.27 GiB
347 cluster@10.0.13.68 1650 137.85 MiB 85.55 KiB 136.63 MiB 14.20 GiB
360 cluster@10.0.13.68 1163 137.65 MiB 121.20 KiB 136.24 MiB 13.23 GiB
323 cluster@10.0.13.68 1267 137.60 MiB 111.21 KiB 136.91 MiB 14.59 GiB
270 cluster@10.0.13.68 1198 136.89 MiB 117.01 KiB 134.72 MiB 13.55 GiB
278 cluster@10.0.13.68 1003 136.76 MiB 139.62 KiB 136.33 MiB 16.33 GiB
259 cluster@10.0.13.68 991 136.74 MiB 141.29 KiB 136.31 MiB 16.77 GiB
266 cluster@10.0.13.68 984 136.69 MiB 142.25 KiB 136.33 MiB 15.35 GiB
348 cluster@10.0.13.68 1031 136.69 MiB 135.76 KiB 136.15 MiB 14.13 GiB
346 cluster@10.0.13.68 1588 136.21 MiB 87.83 KiB 136.69 MiB 17.14 GiB
314 cluster@10.0.13.68 1012 136.05 MiB 137.66 KiB 136.37 MiB 15.07 GiB
279 cluster@10.0.13.68 904 135.81 MiB 153.83 KiB 134.27 MiB 12.29 GiB
312 cluster@10.0.13.68 992 135.76 MiB 140.14 KiB 136.15 MiB 15.62 GiB
290 cluster@10.0.13.68 970 135.70 MiB 143.25 KiB 134.70 MiB 13.54 GiB
305 cluster@10.0.13.68 1123 135.44 MiB 123.50 KiB 136.21 MiB 14.96 GiB
311 cluster@10.0.13.68 1108 134.94 MiB 124.71 KiB 136.33 MiB 16.61 GiB
302 cluster@10.0.13.68 1006 134.80 MiB 137.21 KiB 134.81 MiB 12.75 GiB
243 cluster@10.0.13.68 848 132.64 MiB 160.16 KiB 134.30 MiB 12.67 GiB
334 cluster@10.0.13.68 1779 121.58 MiB 69.98 KiB 118.86 MiB 12.28 GiB
-- trimmed, but current allocated adds up to 10GB which matches memory/sql/Prepared_statement::main_mem_root --
select * from sys.memory_global_by_current_bytes mgbcb ;
event_name current_count current_alloc current_avg_alloc high_count high_alloc high_avg_alloc
memory/sql/Prepared_statement::main_mem_root 13648 10.53 GiB 808.94 KiB 13654 10.53 GiB 808.59 KiB
memory/innodb/buf_buf_pool 24 3.07 GiB 131.00 MiB 24 3.07 GiB 131.00 MiB
memory/mysys/KEY_CACHE 3 256.00 MiB 85.33 MiB 3 256.00 MiB 85.33 MiB
memory/sql/TABLE 24753 136.76 MiB 5.66 KiB 24882 141.67 MiB 5.83 KiB
memory/innodb/hash0hash 32 83.70 MiB 2.62 MiB 32 83.70 MiB 2.62 MiB
memory/innodb/memory 26670 64.23 MiB 2.47 KiB 36774 129.14 MiB 3.60 KiB
memory/performance_schema/table_handles 5 45.31 MiB 9.06 MiB 5 45.31 MiB 9.06 MiB
memory/performance_schema/events_statements_summary_by_digest 1 39.67 MiB 39.67 MiB 1 39.67 MiB 39.67 MiB
memory/innodb/row0sel 1197 33.61 MiB 28.75 KiB 2744 140.74 MiB 52.52 KiB
memory/innodb/buf0dblwr 840 30.15 MiB 36.76 KiB 840 36.54 MiB 44.55 KiB
memory/innodb/ut0link_buf 2 24.00 MiB 12.00 MiB 2 24.00 MiB 12.00 MiB
memory/innodb/lock0lock 9799 21.24 MiB 2.22 KiB 9799 21.24 MiB 2.22 KiB
memory/performance_schema/events_statements_summary_by_thread_by_event_name 2 19.59 MiB 9.79 MiB 2 19.59 MiB 9.79 MiB
memory/performance_schema/memory_summary_by_thread_by_event_name 2 15.82 MiB 7.91 MiB 2 15.82 MiB 7.91 MiB
memory/sql/NET::buff 299 14.04 MiB 48.10 KiB 419 16.57 MiB 40.49 KiB
memory/mysqld_openssl/openssl_malloc 18492 13.92 MiB 789 bytes 56162 26.89 MiB 502 bytes
memory/performance_schema/events_statements_history_long 1 13.89 MiB 13.89 MiB 1 13.89 MiB 13.89 MiB
memory/sql/TABLE_SHARE::mem_root 3532 13.59 MiB 3.94 KiB 3532 13.59 MiB 3.94 KiB
memory/mysys/IO_CACHE 1011 10.53 MiB 10.66 KiB 1013 10.54 MiB 10.66 KiB
memory/performance_schema/events_statements_summary_by_digest.digest_text 1 9.77 MiB 9.77 MiB 1 9.77 MiB 9.77 MiB
memory/performance_schema/events_statements_history_long.digest_text 1 9.77 MiB 9.77 MiB 1 9.77 MiB 9.77 MiB
memory/performance_schema/events_statements_history_long.sql_text 1 9.77 MiB 9.77 MiB 1 9.77 MiB 9.77 MiB
memory/performance_schema/events_waits_summary_by_thread_by_event_name 2 8.66 MiB 4.33 MiB 2 8.66 MiB 4.33 MiB
memory/innodb/ut0new 6 8.08 MiB 1.35 MiB 6 8.08 MiB 1.35 MiB
memory/innodb/ha_innodb 4390 7.27 MiB 1.70 KiB 5749 13.49 MiB 2.40 KiB
.. trimmed ..
memory/sql/errmsgs 1 331.87 KiB 331.87 KiB 1 331.87 KiB 331.87 KiB
memory/vio/vio 298 311.97 KiB 1.05 KiB 306 320.34 KiB 1.05 KiB
memory/innodb/ut0rbt 3067 307.37 KiB 102 bytes 12010 1.08 MiB 94 bytes
memory/innodb/mem0mem 4262 295.59 KiB 71 bytes 4415 302.14 KiB 70 bytes
memory/innodb/read0read 1025 288.28 KiB 288 bytes 1025 288.28 KiB 288 bytes
memory/performance_schema/file_handle 1 256.00 KiB 256.00 KiB 1 256.00 KiB 256.00 KiB
memory/performance_schema/session_connect_attrs 2 256.00 KiB 128.00 KiB 2 256.00 KiB 128.00 KiB
memory/mysys/lf_dynarray 62 250.92 KiB 4.05 KiB 62 250.92 KiB 4.05 KiB
memory/mysys/lf_slist 6992 218.50 KiB 32 bytes 6992 218.50 KiB 32 bytes
memory/sql/plugin_mem_root 66 201.02 KiB 3.05 KiB 66 201.02 KiB 3.05 KiB
memory/innodb/trx0i_s 2 200.19 KiB 100.09 KiB 2 200.19 KiB 100.09 KiB
memory/sql/THD::Session_tracker 3978 198.72 KiB 51 bytes 4083 204.00 KiB 51 bytes
memory/innodb/trx0undo 509 178.95 KiB 360 bytes 46613 16.00 MiB 360 bytes
memory/sql/Prepared_statement_map 3742 160.14 KiB 43 bytes 3745 175.16 KiB 47 bytes
trimmed.
MySQL tuner run (on the 32Gb database, but told it to assume 8Gb ram)
>> MySQLTuner 1.7.20 - Major Hayden <major@mhtx.net>
>> Bug reports, feature requests, and downloads at http://mysqltuner.pl/
[--] Assuming 8000 MB of physical memory
[--] Assuming 100 MB of swap space
[OK] Currently running supported MySQL version 8.0.21
-------- Storage Engine Statistics -----------------------------------------------------------------
[--] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MEMORY +MRG_MYISAM +MyISAM +PERFORMANCE_SCHEMA
[--] Data in InnoDB tables: 77.7G (Tables: 1646)
[OK] Total fragmented tables: 0
-------- Analysis Performance Metrics --------------------------------------------------------------
[--] innodb_stats_on_metadata: OFF
[OK] No stat updates during querying INFORMATION_SCHEMA.
-------- Performance Metrics -----------------------------------------------------------------------
[--] Up for: 2d 19h 22m 24s (27M q [113.270 qps], 1K conn, TX: 28G, RX: 7G)
[--] Reads / Writes: 73% / 27%
[--] Binary logging is enabled (GTID MODE: OFF_PERMISSIVE)
[--] Physical Memory : 7.8G
[--] Max MySQL memory : 6.5G
[--] Other process memory: 0B
[--] Total buffers: 3.3G global + 10.5M per thread (320 max threads)
[--] P_S Max memory usage: 72B
[--] Galera GCache Max memory usage: 0B
[OK] Maximum reached memory usage: 6.4G (81.89% of installed RAM)
[OK] Maximum possible memory usage: 6.5G (83.73% of installed RAM)
[OK] Overall possible memory usage with other process is compatible with memory available
[OK] Slow queries: 0% (0/27M)
[!!] Highest connection usage: 95% (306/320)
[OK] Aborted connections: 0.00% (0/1176)
[!!] name resolution is active : a reverse name resolution is made for each new connection and can reduce performance
[--] Query cache have been removed in MySQL 8
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 687K sorts)
[OK] No joins without indexes
[!!] Temporary tables created on disk: 85% (249K on disk / 290K total)
[OK] Thread cache hit rate: 73% (306 created / 1K connections)
[!!] Table cache hit rate: 4% (4K open / 98K opened)
[OK] table_definition_cache(2000) is upper than number of tables(1977)
[OK] Open file limit used: 0% (107/65K)
[OK] Table locks acquired immediately: 100% (18K immediate / 18K locks)
[OK] Binlog cache memory access: 99.99% (7214683 Memory / 7215088 Total)
-------- Performance schema ------------------------------------------------------------------------
[--] Memory used by P_S: 72B
[--] Sys schema is installed.
-------- ThreadPool Metrics ------------------------------------------------------------------------
[--] ThreadPool stat is disabled.
-------- InnoDB Metrics ----------------------------------------------------------------------------
[--] InnoDB is enabled.
[--] InnoDB Thread Concurrency: 32
[OK] InnoDB File per table is activated
[!!] InnoDB buffer pool / data size: 3.0G/77.7G
[!!] Ratio InnoDB log file size / InnoDB Buffer pool size (16.6666666666667 %): 256.0M * 2/3.0G should be equal to 25%
[!!] InnoDB buffer pool instances: 4
[--] Number of InnoDB Buffer Pool Chunk : 24 for 4 Buffer Pool Instance(s)
[OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances
[OK] InnoDB Read buffer efficiency: 99.87% (495469607 hits/ 496112175 total)
[!!] InnoDB Write Log efficiency: 72.33% (61616573 hits/ 85189070 total)
[OK] InnoDB log waits: 0.00% (0 waits / 23572497 writes)
-------- Replication Metrics -----------------------------------------------------------------------
[--] Galera Synchronous replication: NO
[--] No replication slave(s) for this server.
[--] Binlog format: ROW
[--] XA support enabled: ON
[--] Semi synchronous replication Master: Not Activated
[--] Semi synchronous replication Slave: Not Activated
[--] This is a standalone server
-------- Recommendations ---------------------------------------------------------------------------
General recommendations:
Reduce or eliminate persistent connections to reduce connection usage
Reduce your SELECT DISTINCT queries which have no LIMIT clause
Increase table_open_cache gradually to avoid file descriptor limits
Read this before increasing table_open_cache over 64:
Beware that open_files_limit (65535) variable
should be greater than table_open_cache (4096)
Before changing innodb_log_file_size and/or innodb_log_files_in_group read this:
Variables to adjust:
max_connections (> 320)
wait_timeout (< 28800)
interactive_timeout (< 28800)
tmp_table_size (> 2M)
max_heap_table_size (> 128M)
table_open_cache (> 4096)
innodb_buffer_pool_size (>= 77.7G) if possible.
innodb_log_file_size should be (=384M) if possible, so InnoDB total log files size equals to 25% of buffer pool size.
innodb_buffer_pool_instances(=3)
show variables;
activate_all_roles_on_login OFF
autocommit ON
back_log 320
big_tables OFF
bind_address *
binlog_cache_size 32768
binlog_checksum NONE
binlog_direct_non_transactional_updates OFF
binlog_encryption OFF
binlog_error_action ABORT_SERVER
binlog_expire_logs_seconds 2592000
binlog_format ROW
binlog_group_commit_sync_delay 0
binlog_group_commit_sync_no_delay_count 0
binlog_gtid_simple_recovery ON
binlog_max_flush_queue_time 0
binlog_order_commits ON
binlog_rotate_encryption_master_key_at_startup OFF
binlog_row_event_max_size 8192
binlog_row_image FULL
binlog_row_metadata MINIMAL
binlog_row_value_options
binlog_rows_query_log_events OFF
binlog_stmt_cache_size 32768
binlog_transaction_compression OFF
binlog_transaction_compression_level_zstd 3
binlog_transaction_dependency_history_size 25000
binlog_transaction_dependency_tracking COMMIT_ORDER
bulk_insert_buffer_size 8388608
character_set_client utf8mb4
character_set_connection utf8mb4
character_set_database utf8mb4
character_set_filesystem binary
character_set_results
character_set_server utf8mb4
character_set_system utf8
check_proxy_users OFF
collation_connection utf8mb4_0900_ai_ci
collation_database utf8mb4_unicode_ci
collation_server utf8mb4_unicode_ci
completion_type NO_CHAIN
concurrent_insert AUTO
connect_timeout 10
core_file OFF
create_admin_listener_thread OFF
cte_max_recursion_depth 1000
default_collation_for_utf8mb4 utf8mb4_0900_ai_ci
default_storage_engine InnoDB
default_table_encryption OFF
default_tmp_storage_engine InnoDB
default_week_format 0
delay_key_write ON
delayed_insert_limit 100
delayed_insert_timeout 300
delayed_queue_size 1000
disabled_storage_engines
disconnect_on_expired_password ON
div_precision_increment 4
end_markers_in_json OFF
enforce_gtid_consistency OFF
eq_range_index_dive_limit 200
error_count 0
event_scheduler ON
expire_logs_days 0
explicit_defaults_for_timestamp ON
flush OFF
flush_time 0
foreign_key_checks ON
ft_boolean_syntax + -><()~*:""&|
ft_max_word_len 84
ft_min_word_len 4
ft_query_expansion_limit 20
ft_stopword_file (built-in)
generated_random_password_length 20
group_concat_max_len 1024
group_replication_consistency EVENTUAL
gtid_executed
gtid_executed_compression_period 1000
gtid_mode OFF_PERMISSIVE
gtid_next AUTOMATIC
gtid_owned
gtid_purged
have_compress YES
have_dynamic_loading YES
have_geometry YES
have_openssl YES
have_profiling YES
have_query_cache NO
have_rtree_keys YES
have_ssl YES
have_statement_timeout YES
histogram_generation_max_mem_size 20000000
host_cache_size 448
identity 0
immediate_server_version 999999
information_schema_stats_expiry 86400
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 4
innodb_buffer_pool_load_abort OFF
innodb_buffer_pool_load_at_startup ON
innodb_buffer_pool_load_now OFF
innodb_buffer_pool_size 3221225472
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_deadlock_detect ON
innodb_dedicated_server OFF
innodb_default_row_format dynamic
innodb_disable_sort_file_cache OFF
innodb_doublewrite ON
innodb_doublewrite_batch_size 16
innodb_doublewrite_files 2
innodb_doublewrite_pages 32
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 2
innodb_flush_method O_DIRECT
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 5
innodb_log_buffer_size 8388608
innodb_log_checksums ON
innodb_log_compressed_pages ON
innodb_log_file_size 268435456
innodb_log_files_in_group 2
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_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 4096
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 1
innodb_random_read_ahead OFF
innodb_read_ahead_threshold 56
innodb_read_io_threads 16
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_thread_concurrency 32
innodb_thread_sleep_delay 0
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 8.0.21
innodb_write_io_threads 16
insert_id 0
interactive_timeout 28800
internal_tmp_mem_storage_engine TempTable
join_buffer_size 262144
keep_files_on_create OFF
key_buffer_size 268435456
key_cache_age_threshold 300
key_cache_block_size 1024
key_cache_division_limit 100
keyring_operations ON
large_files_support ON
large_page_size 0
large_pages OFF
last_insert_id 0
lc_messages en_US
lc_time_names en_US
license GPL
local_infile ON
lock_wait_timeout 31536000
locked_in_memory OFF
log_bin ON
log_bin_basename /rdsdbdata/log/binlog/mysql-bin-changelog
log_bin_index /rdsdbdata/log/binlog/mysql-bin-changelog.index
log_bin_trust_function_creators OFF
log_bin_use_v1_row_events OFF
log_error /rdsdbdata/log/error/mysql-error.log
log_error_services log_filter_internal; log_sink_internal
log_error_suppression_list
log_error_verbosity 2
log_output TABLE
log_queries_not_using_indexes OFF
log_raw OFF
log_slave_updates ON
log_slow_admin_statements OFF
log_slow_extra OFF
log_slow_slave_statements OFF
log_statements_unsafe_for_binlog OFF
log_throttle_queries_not_using_indexes 0
log_timestamps UTC
long_query_time 5.000000
low_priority_updates OFF
lower_case_file_system OFF
lower_case_table_names 0
mandatory_roles
master_info_repository TABLE
master_verify_checksum OFF
max_allowed_packet 4194304
max_binlog_cache_size 18446744073709547520
max_binlog_size 134217728
max_binlog_stmt_cache_size 18446744073709547520
max_connect_errors 100
max_connections 320
max_delayed_threads 20
max_digest_length 1024
max_error_count 1024
max_execution_time 0
max_heap_table_size 134217728
max_insert_delayed_threads 20
max_join_size 18446744073709551615
max_length_for_sort_data 4096
max_points_in_geometry 65536
max_prepared_stmt_count 16382
max_relay_log_size 0
max_seeks_for_key 18446744073709551615
max_sort_length 1024
max_sp_recursion_depth 0
max_user_connections 0
max_write_lock_count 18446744073709551615
min_examined_row_limit 0
myisam_data_pointer_size 6
myisam_max_sort_file_size 9223372036853727232
myisam_mmap_size 18446744073709551615
myisam_recover_options OFF
myisam_repair_threads 1
myisam_sort_buffer_size 8388608
myisam_stats_method nulls_unequal
myisam_use_mmap OFF
mysql_native_password_proxy_users OFF
net_buffer_length 16384
net_read_timeout 30
net_retry_count 10
net_write_timeout 60
new OFF
ngram_token_size 2
offline_mode OFF
old OFF
old_alter_table OFF
open_files_limit 65535
optimizer_prune_level 1
optimizer_search_depth 62
optimizer_switch index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on,use_invisible_indexes=off,skip_scan=on,hash_join=on,subquery_to_derived=off,prefer_ordering_index=on
optimizer_trace enabled=off,one_line=off
optimizer_trace_features greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
optimizer_trace_limit 1
optimizer_trace_max_mem_size 1048576
optimizer_trace_offset -1
original_commit_timestamp 36028797018963968
original_server_version 999999
parser_max_mem_size 18446744073709551615
partial_revokes OFF
password_history 0
password_require_current OFF
password_reuse_interval 0
performance_schema ON
performance_schema_accounts_size -1
performance_schema_digests_size 10000
performance_schema_error_size 0
performance_schema_events_stages_history_long_size 10000
performance_schema_events_stages_history_size 10
performance_schema_events_statements_history_long_size 10000
performance_schema_events_statements_history_size 10
performance_schema_events_transactions_history_long_size 10000
performance_schema_events_transactions_history_size 10
performance_schema_events_waits_history_long_size 10000
performance_schema_events_waits_history_size 10
performance_schema_hosts_size -1
performance_schema_max_cond_classes 100
performance_schema_max_cond_instances -1
performance_schema_max_digest_length 1024
performance_schema_max_digest_sample_age 60
performance_schema_max_file_classes 80
performance_schema_max_file_handles 32768
performance_schema_max_file_instances -1
performance_schema_max_index_stat -1
performance_schema_max_memory_classes 450
performance_schema_max_metadata_locks -1
performance_schema_max_mutex_classes 300
performance_schema_max_mutex_instances -1
performance_schema_max_prepared_statements_instances -1
performance_schema_max_program_instances -1
performance_schema_max_rwlock_classes 60
performance_schema_max_rwlock_instances -1
performance_schema_max_socket_classes 10
performance_schema_max_socket_instances -1
performance_schema_max_sql_text_length 1024
performance_schema_max_stage_classes 175
performance_schema_max_statement_classes 218
performance_schema_max_statement_stack 10
performance_schema_max_table_handles -1
performance_schema_max_table_instances -1
performance_schema_max_table_lock_stat -1
performance_schema_max_thread_classes 100
performance_schema_max_thread_instances -1
performance_schema_session_connect_attrs_size 512
performance_schema_setup_actors_size -1
performance_schema_setup_objects_size -1
performance_schema_users_size -1
persist_only_admin_x509_subject
persisted_globals_load OFF
port 3306
preload_buffer_size 32768
print_identified_with_as_hex OFF
profiling OFF
profiling_history_size 15
protocol_compression_algorithms zlib,zstd,uncompressed
protocol_version 10
proxy_user
pseudo_slave_mode OFF
pseudo_thread_id 1164
query_alloc_block_size 8192
query_prealloc_size 8192
rand_seed1 0
rand_seed2 0
range_alloc_block_size 4096
range_optimizer_max_mem_size 8388608
rbr_exec_mode STRICT
read_buffer_size 1048576
read_only OFF
read_rnd_buffer_size 4194304
regexp_stack_limit 8000000
regexp_time_limit 32
relay_log /rdsdbdata/log/relaylog/relaylog
relay_log_basename /rdsdbdata/log/relaylog/relaylog
relay_log_index /rdsdbdata/log/relaylog/relaylog.index
relay_log_info_file relay-log.info
relay_log_info_repository TABLE
relay_log_purge ON
relay_log_recovery ON
relay_log_space_limit 0
report_host
report_password
report_port 3306
report_user
require_row_format OFF
require_secure_transport OFF
resultset_metadata FULL
rpl_read_size 8192
rpl_stop_slave_timeout 31536000
schema_definition_cache 256
secondary_engine_cost_threshold 100000.000000
secure_file_priv /tmp/
server_id 658899241
server_id_bits 32
server_uuid b2a6c6b9-d398-11e6-b6a4-12306f56ae16
session_track_gtids OFF
session_track_schema ON
session_track_state_change OFF
session_track_system_variables time_zone,autocommit,character_set_client,character_set_results,character_set_connection
session_track_transaction_info OFF
sha256_password_auto_generate_rsa_keys ON
sha256_password_private_key_path private_key.pem
sha256_password_proxy_users OFF
sha256_password_public_key_path public_key.pem
show_create_table_skip_secondary_engine OFF
show_create_table_verbosity OFF
show_old_temporals OFF
skip_external_locking ON
skip_name_resolve OFF
skip_networking OFF
skip_show_database OFF
slave_allow_batching OFF
slave_checkpoint_group 512
slave_checkpoint_period 300
slave_compressed_protocol OFF
slave_exec_mode IDEMPOTENT
slave_max_allowed_packet 1073741824
slave_net_timeout 60
slave_parallel_type DATABASE
slave_parallel_workers 0
slave_pending_jobs_size_max 134217728
slave_preserve_commit_order OFF
slave_rows_search_algorithms INDEX_SCAN,HASH_SCAN
slave_skip_errors OFF
slave_sql_verify_checksum ON
slave_transaction_retries 10
slave_type_conversions
slow_launch_time 2
slow_query_log ON
slow_query_log_file /rdsdbdata/log/slowquery/mysql-slowquery.log
socket /tmp/mysql.sock
sort_buffer_size 1048576
sql_auto_is_null OFF
sql_big_selects ON
sql_buffer_result OFF
sql_log_bin ON
sql_log_off OFF
sql_mode STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION
sql_notes ON
sql_quote_show_create ON
sql_require_primary_key OFF
sql_safe_updates OFF
sql_select_limit 20000
sql_slave_skip_counter 0
sql_warnings OFF
ssl_ca /rdsdbdata/rds-metadata/ca-cert.pem
ssl_capath
ssl_cert /rdsdbdata/rds-metadata/server-cert.pem
ssl_cipher ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA:AES128-SHA:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA:DHE-DSS-AES128-SHA:DHE-DSS-AES256-SHA
ssl_crl
ssl_crlpath
ssl_fips_mode OFF
ssl_key /rdsdbdata/rds-metadata/server-key.pem
stored_program_cache 256
stored_program_definition_cache 256
super_read_only OFF
sync_binlog 1
sync_master_info 10000
sync_relay_log 10000
sync_relay_log_info 10000
system_time_zone UTC
table_definition_cache 2000
table_encryption_privilege_check OFF
table_open_cache 4096
table_open_cache_instances 16
tablespace_definition_cache 256
temptable_max_ram 1073741824
temptable_use_mmap ON
thread_cache_size 11
thread_handling one-thread-per-connection
thread_stack 262144
time_zone UTC
timestamp 1610991021.519301
tls_ciphersuites
tls_version TLSv1,TLSv1.1,TLSv1.2,TLSv1.3
tmp_table_size 2097152
transaction_alloc_block_size 8192
transaction_allow_batching OFF
transaction_isolation REPEATABLE-READ
transaction_prealloc_size 4096
transaction_read_only OFF
transaction_write_set_extraction XXHASH64
unique_checks ON
updatable_views_with_limit YES
use_secondary_engine ON
version 8.0.21
version_comment Source distribution
version_compile_machine aarch64
version_compile_os Linux
version_compile_zlib 1.2.11
wait_timeout 28800
warning_count 0
windowing_use_high_precision ON
在此处显示状态等。
https://gist.github.com/DaveB93/138f6bac254fee5bbbbb7ce2af7c2fef
您计算的每线程内存使用量有误。这些变量（以及您未包含的 tmp_table_size ）并非同时使用。不要把它们加起来。即使你将它们加起来，至少有两个可能会被分配多次用于单个查询，所以你不能只是将它们相加。
基本上，MySQLTuner 计算的内存使用量完全是误导，您不应该相信它。我之前写过：What does "MySQL's maximum memory usage is dangerously high" mean by mysqltuner?
如果您想了解 实际 内存使用情况，请使用 PERFORMANCE_SCHEMA，或者在 SYS 架构中更容易阅读的视图。
PS 或 SYS 的文档非常密集，因此我会在像这样的博客中寻找更好的示例：
https://www.percona.com/blog/2020/11/02/understanding-mysql-memory-usage-with-performance-schema/
我们最近在几台服务器上从 mysql 5.6 升级到 mysql 8.0，其中一台服务器很好，没有问题，但它 负载明显低于我们的其他服务器 运行 内存不足的服务器之一。
我们的服务器启动，然后获取 300 个连接，并使用 C3P0 池将它们保持打开到 mysql 服务器。
我们在 MySQL 5.6 上的 AWS 上 运行 这些服务器在 8GB RAM 上具有相同的覆盖参数，当我们升级到 MySQL 8.0.21 时，我们开始 运行 大约 1 天内存不足。我们将服务器增加到 32Gb 但没有更改参数。它已使用超过 15 GB，并且还在增加。
我们很确定它与每个连接线程内存有关，但不确定原因。从 MySQL 调谐器来看，控制每个线程内存的变量似乎是：
read_buffer_size 1048576
read_rnd_buffer_size 4194304
sort_buffer_size 1048576
thread_stack 262144
max_allowed_packet 4194304
join_buffer_size 262144
总共有 10.5 Mb。我在这里缺少变量吗？
查看 memory_by_thread_by_current_bytes 我们有超过 200Mb 的连接
服务器是 运行AWS RDS 上的 8.0.21
还有其他问题我应该 运行 弄清楚是什么占用了线程上的所有这些 ram？
通常 innodb 缓冲池是 4GB，但是当我们在 8GB 的机器上为了多一点空间时，我们把它降到了 3GB。
select * from sys.memory_by_thread_by_current_bytes;
thread_id `user` current_count_used current_allocated current_avg_alloc current_max_alloc total_allocated
315 cluster@10.0.13.68 1880 209.77 MiB 114.26 KiB 204.10 MiB 21.51 GiB
336 cluster@10.0.13.68 2288 207.75 MiB 92.98 KiB 204.10 MiB 23.38 GiB
358 cluster@10.0.13.68 1847 207.35 MiB 114.96 KiB 204.01 MiB 19.66 GiB
272 cluster@10.0.13.68 1347 205.59 MiB 156.29 KiB 204.77 MiB 24.91 GiB
328 cluster@10.0.13.68 1825 204.55 MiB 114.77 KiB 204.14 MiB 23.84 GiB
276 cluster@10.0.13.68 1486 204.08 MiB 140.63 KiB 201.70 MiB 21.31 GiB
313 cluster@10.0.13.68 975 203.05 MiB 213.26 KiB 203.56 MiB 19.70 GiB
258 cluster@10.0.13.68 1244 202.76 MiB 166.91 KiB 201.56 MiB 19.58 GiB
288 cluster@10.0.13.68 1431 201.49 MiB 144.19 KiB 201.48 MiB 19.39 GiB
248 cluster@10.0.13.68 1265 175.83 MiB 142.33 KiB 175.15 MiB 17.04 GiB
284 cluster@10.0.13.68 978 174.08 MiB 182.27 KiB 175.34 MiB 18.25 GiB
343 cluster@10.0.13.68 2038 143.98 MiB 72.34 KiB 139.14 MiB 16.84 GiB
329 cluster@10.0.13.68 1971 142.77 MiB 74.17 KiB 138.54 MiB 17.93 GiB
355 cluster@10.0.13.68 1646 141.74 MiB 88.18 KiB 136.37 MiB 15.04 GiB
327 cluster@10.0.13.68 1805 139.95 MiB 79.39 KiB 136.15 MiB 15.95 GiB
330 cluster@10.0.13.68 2001 139.72 MiB 71.50 KiB 136.08 MiB 14.69 GiB
351 cluster@10.0.13.68 2129 139.45 MiB 67.07 KiB 136.57 MiB 16.34 GiB
316 cluster@10.0.13.68 1598 139.01 MiB 89.08 KiB 136.46 MiB 17.56 GiB
293 cluster@10.0.13.68 1238 138.29 MiB 114.39 KiB 136.24 MiB 15.53 GiB
345 cluster@10.0.13.68 1196 137.95 MiB 118.11 KiB 137.40 MiB 15.27 GiB
347 cluster@10.0.13.68 1650 137.85 MiB 85.55 KiB 136.63 MiB 14.20 GiB
360 cluster@10.0.13.68 1163 137.65 MiB 121.20 KiB 136.24 MiB 13.23 GiB
323 cluster@10.0.13.68 1267 137.60 MiB 111.21 KiB 136.91 MiB 14.59 GiB
270 cluster@10.0.13.68 1198 136.89 MiB 117.01 KiB 134.72 MiB 13.55 GiB
278 cluster@10.0.13.68 1003 136.76 MiB 139.62 KiB 136.33 MiB 16.33 GiB
259 cluster@10.0.13.68 991 136.74 MiB 141.29 KiB 136.31 MiB 16.77 GiB
266 cluster@10.0.13.68 984 136.69 MiB 142.25 KiB 136.33 MiB 15.35 GiB
348 cluster@10.0.13.68 1031 136.69 MiB 135.76 KiB 136.15 MiB 14.13 GiB
346 cluster@10.0.13.68 1588 136.21 MiB 87.83 KiB 136.69 MiB 17.14 GiB
314 cluster@10.0.13.68 1012 136.05 MiB 137.66 KiB 136.37 MiB 15.07 GiB
279 cluster@10.0.13.68 904 135.81 MiB 153.83 KiB 134.27 MiB 12.29 GiB
312 cluster@10.0.13.68 992 135.76 MiB 140.14 KiB 136.15 MiB 15.62 GiB
290 cluster@10.0.13.68 970 135.70 MiB 143.25 KiB 134.70 MiB 13.54 GiB
305 cluster@10.0.13.68 1123 135.44 MiB 123.50 KiB 136.21 MiB 14.96 GiB
311 cluster@10.0.13.68 1108 134.94 MiB 124.71 KiB 136.33 MiB 16.61 GiB
302 cluster@10.0.13.68 1006 134.80 MiB 137.21 KiB 134.81 MiB 12.75 GiB
243 cluster@10.0.13.68 848 132.64 MiB 160.16 KiB 134.30 MiB 12.67 GiB
334 cluster@10.0.13.68 1779 121.58 MiB 69.98 KiB 118.86 MiB 12.28 GiB
-- trimmed, but current allocated adds up to 10GB which matches memory/sql/Prepared_statement::main_mem_root --
select * from sys.memory_global_by_current_bytes mgbcb ;
event_name current_count current_alloc current_avg_alloc high_count high_alloc high_avg_alloc
memory/sql/Prepared_statement::main_mem_root 13648 10.53 GiB 808.94 KiB 13654 10.53 GiB 808.59 KiB
memory/innodb/buf_buf_pool 24 3.07 GiB 131.00 MiB 24 3.07 GiB 131.00 MiB
memory/mysys/KEY_CACHE 3 256.00 MiB 85.33 MiB 3 256.00 MiB 85.33 MiB
memory/sql/TABLE 24753 136.76 MiB 5.66 KiB 24882 141.67 MiB 5.83 KiB
memory/innodb/hash0hash 32 83.70 MiB 2.62 MiB 32 83.70 MiB 2.62 MiB
memory/innodb/memory 26670 64.23 MiB 2.47 KiB 36774 129.14 MiB 3.60 KiB
memory/performance_schema/table_handles 5 45.31 MiB 9.06 MiB 5 45.31 MiB 9.06 MiB
memory/performance_schema/events_statements_summary_by_digest 1 39.67 MiB 39.67 MiB 1 39.67 MiB 39.67 MiB
memory/innodb/row0sel 1197 33.61 MiB 28.75 KiB 2744 140.74 MiB 52.52 KiB
memory/innodb/buf0dblwr 840 30.15 MiB 36.76 KiB 840 36.54 MiB 44.55 KiB
memory/innodb/ut0link_buf 2 24.00 MiB 12.00 MiB 2 24.00 MiB 12.00 MiB
memory/innodb/lock0lock 9799 21.24 MiB 2.22 KiB 9799 21.24 MiB 2.22 KiB
memory/performance_schema/events_statements_summary_by_thread_by_event_name 2 19.59 MiB 9.79 MiB 2 19.59 MiB 9.79 MiB
memory/performance_schema/memory_summary_by_thread_by_event_name 2 15.82 MiB 7.91 MiB 2 15.82 MiB 7.91 MiB
memory/sql/NET::buff 299 14.04 MiB 48.10 KiB 419 16.57 MiB 40.49 KiB
memory/mysqld_openssl/openssl_malloc 18492 13.92 MiB 789 bytes 56162 26.89 MiB 502 bytes
memory/performance_schema/events_statements_history_long 1 13.89 MiB 13.89 MiB 1 13.89 MiB 13.89 MiB
memory/sql/TABLE_SHARE::mem_root 3532 13.59 MiB 3.94 KiB 3532 13.59 MiB 3.94 KiB
memory/mysys/IO_CACHE 1011 10.53 MiB 10.66 KiB 1013 10.54 MiB 10.66 KiB
memory/performance_schema/events_statements_summary_by_digest.digest_text 1 9.77 MiB 9.77 MiB 1 9.77 MiB 9.77 MiB
memory/performance_schema/events_statements_history_long.digest_text 1 9.77 MiB 9.77 MiB 1 9.77 MiB 9.77 MiB
memory/performance_schema/events_statements_history_long.sql_text 1 9.77 MiB 9.77 MiB 1 9.77 MiB 9.77 MiB
memory/performance_schema/events_waits_summary_by_thread_by_event_name 2 8.66 MiB 4.33 MiB 2 8.66 MiB 4.33 MiB
memory/innodb/ut0new 6 8.08 MiB 1.35 MiB 6 8.08 MiB 1.35 MiB
memory/innodb/ha_innodb 4390 7.27 MiB 1.70 KiB 5749 13.49 MiB 2.40 KiB
.. trimmed ..
memory/sql/errmsgs 1 331.87 KiB 331.87 KiB 1 331.87 KiB 331.87 KiB
memory/vio/vio 298 311.97 KiB 1.05 KiB 306 320.34 KiB 1.05 KiB
memory/innodb/ut0rbt 3067 307.37 KiB 102 bytes 12010 1.08 MiB 94 bytes
memory/innodb/mem0mem 4262 295.59 KiB 71 bytes 4415 302.14 KiB 70 bytes
memory/innodb/read0read 1025 288.28 KiB 288 bytes 1025 288.28 KiB 288 bytes
memory/performance_schema/file_handle 1 256.00 KiB 256.00 KiB 1 256.00 KiB 256.00 KiB
memory/performance_schema/session_connect_attrs 2 256.00 KiB 128.00 KiB 2 256.00 KiB 128.00 KiB
memory/mysys/lf_dynarray 62 250.92 KiB 4.05 KiB 62 250.92 KiB 4.05 KiB
memory/mysys/lf_slist 6992 218.50 KiB 32 bytes 6992 218.50 KiB 32 bytes
memory/sql/plugin_mem_root 66 201.02 KiB 3.05 KiB 66 201.02 KiB 3.05 KiB
memory/innodb/trx0i_s 2 200.19 KiB 100.09 KiB 2 200.19 KiB 100.09 KiB
memory/sql/THD::Session_tracker 3978 198.72 KiB 51 bytes 4083 204.00 KiB 51 bytes
memory/innodb/trx0undo 509 178.95 KiB 360 bytes 46613 16.00 MiB 360 bytes
memory/sql/Prepared_statement_map 3742 160.14 KiB 43 bytes 3745 175.16 KiB 47 bytes
trimmed.
MySQL tuner run (on the 32Gb database, but told it to assume 8Gb ram)
>> MySQLTuner 1.7.20 - Major Hayden <major@mhtx.net>
>> Bug reports, feature requests, and downloads at http://mysqltuner.pl/
[--] Assuming 8000 MB of physical memory
[--] Assuming 100 MB of swap space
[OK] Currently running supported MySQL version 8.0.21
-------- Storage Engine Statistics -----------------------------------------------------------------
[--] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MEMORY +MRG_MYISAM +MyISAM +PERFORMANCE_SCHEMA
[--] Data in InnoDB tables: 77.7G (Tables: 1646)
[OK] Total fragmented tables: 0
-------- Analysis Performance Metrics --------------------------------------------------------------
[--] innodb_stats_on_metadata: OFF
[OK] No stat updates during querying INFORMATION_SCHEMA.
-------- Performance Metrics -----------------------------------------------------------------------
[--] Up for: 2d 19h 22m 24s (27M q [113.270 qps], 1K conn, TX: 28G, RX: 7G)
[--] Reads / Writes: 73% / 27%
[--] Binary logging is enabled (GTID MODE: OFF_PERMISSIVE)
[--] Physical Memory : 7.8G
[--] Max MySQL memory : 6.5G
[--] Other process memory: 0B
[--] Total buffers: 3.3G global + 10.5M per thread (320 max threads)
[--] P_S Max memory usage: 72B
[--] Galera GCache Max memory usage: 0B
[OK] Maximum reached memory usage: 6.4G (81.89% of installed RAM)
[OK] Maximum possible memory usage: 6.5G (83.73% of installed RAM)
[OK] Overall possible memory usage with other process is compatible with memory available
[OK] Slow queries: 0% (0/27M)
[!!] Highest connection usage: 95% (306/320)
[OK] Aborted connections: 0.00% (0/1176)
[!!] name resolution is active : a reverse name resolution is made for each new connection and can reduce performance
[--] Query cache have been removed in MySQL 8
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 687K sorts)
[OK] No joins without indexes
[!!] Temporary tables created on disk: 85% (249K on disk / 290K total)
[OK] Thread cache hit rate: 73% (306 created / 1K connections)
[!!] Table cache hit rate: 4% (4K open / 98K opened)
[OK] table_definition_cache(2000) is upper than number of tables(1977)
[OK] Open file limit used: 0% (107/65K)
[OK] Table locks acquired immediately: 100% (18K immediate / 18K locks)
[OK] Binlog cache memory access: 99.99% (7214683 Memory / 7215088 Total)
-------- Performance schema ------------------------------------------------------------------------
[--] Memory used by P_S: 72B
[--] Sys schema is installed.
-------- ThreadPool Metrics ------------------------------------------------------------------------
[--] ThreadPool stat is disabled.
-------- InnoDB Metrics ----------------------------------------------------------------------------
[--] InnoDB is enabled.
[--] InnoDB Thread Concurrency: 32
[OK] InnoDB File per table is activated
[!!] InnoDB buffer pool / data size: 3.0G/77.7G
[!!] Ratio InnoDB log file size / InnoDB Buffer pool size (16.6666666666667 %): 256.0M * 2/3.0G should be equal to 25%
[!!] InnoDB buffer pool instances: 4
[--] Number of InnoDB Buffer Pool Chunk : 24 for 4 Buffer Pool Instance(s)
[OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances
[OK] InnoDB Read buffer efficiency: 99.87% (495469607 hits/ 496112175 total)
[!!] InnoDB Write Log efficiency: 72.33% (61616573 hits/ 85189070 total)
[OK] InnoDB log waits: 0.00% (0 waits / 23572497 writes)
-------- Replication Metrics -----------------------------------------------------------------------
[--] Galera Synchronous replication: NO
[--] No replication slave(s) for this server.
[--] Binlog format: ROW
[--] XA support enabled: ON
[--] Semi synchronous replication Master: Not Activated
[--] Semi synchronous replication Slave: Not Activated
[--] This is a standalone server
-------- Recommendations ---------------------------------------------------------------------------
General recommendations:
Reduce or eliminate persistent connections to reduce connection usage
Reduce your SELECT DISTINCT queries which have no LIMIT clause
Increase table_open_cache gradually to avoid file descriptor limits
Read this before increasing table_open_cache over 64:
Beware that open_files_limit (65535) variable
should be greater than table_open_cache (4096)
Before changing innodb_log_file_size and/or innodb_log_files_in_group read this:
Variables to adjust:
max_connections (> 320)
wait_timeout (< 28800)
interactive_timeout (< 28800)
tmp_table_size (> 2M)
max_heap_table_size (> 128M)
table_open_cache (> 4096)
innodb_buffer_pool_size (>= 77.7G) if possible.
innodb_log_file_size should be (=384M) if possible, so InnoDB total log files size equals to 25% of buffer pool size.
innodb_buffer_pool_instances(=3)
show variables;
activate_all_roles_on_login OFF
autocommit ON
back_log 320
big_tables OFF
bind_address *
binlog_cache_size 32768
binlog_checksum NONE
binlog_direct_non_transactional_updates OFF
binlog_encryption OFF
binlog_error_action ABORT_SERVER
binlog_expire_logs_seconds 2592000
binlog_format ROW
binlog_group_commit_sync_delay 0
binlog_group_commit_sync_no_delay_count 0
binlog_gtid_simple_recovery ON
binlog_max_flush_queue_time 0
binlog_order_commits ON
binlog_rotate_encryption_master_key_at_startup OFF
binlog_row_event_max_size 8192
binlog_row_image FULL
binlog_row_metadata MINIMAL
binlog_row_value_options
binlog_rows_query_log_events OFF
binlog_stmt_cache_size 32768
binlog_transaction_compression OFF
binlog_transaction_compression_level_zstd 3
binlog_transaction_dependency_history_size 25000
binlog_transaction_dependency_tracking COMMIT_ORDER
bulk_insert_buffer_size 8388608
character_set_client utf8mb4
character_set_connection utf8mb4
character_set_database utf8mb4
character_set_filesystem binary
character_set_results
character_set_server utf8mb4
character_set_system utf8
check_proxy_users OFF
collation_connection utf8mb4_0900_ai_ci
collation_database utf8mb4_unicode_ci
collation_server utf8mb4_unicode_ci
completion_type NO_CHAIN
concurrent_insert AUTO
connect_timeout 10
core_file OFF
create_admin_listener_thread OFF
cte_max_recursion_depth 1000
default_collation_for_utf8mb4 utf8mb4_0900_ai_ci
default_storage_engine InnoDB
default_table_encryption OFF
default_tmp_storage_engine InnoDB
default_week_format 0
delay_key_write ON
delayed_insert_limit 100
delayed_insert_timeout 300
delayed_queue_size 1000
disabled_storage_engines
disconnect_on_expired_password ON
div_precision_increment 4
end_markers_in_json OFF
enforce_gtid_consistency OFF
eq_range_index_dive_limit 200
error_count 0
event_scheduler ON
expire_logs_days 0
explicit_defaults_for_timestamp ON
flush OFF
flush_time 0
foreign_key_checks ON
ft_boolean_syntax + -><()~*:""&|
ft_max_word_len 84
ft_min_word_len 4
ft_query_expansion_limit 20
ft_stopword_file (built-in)
generated_random_password_length 20
group_concat_max_len 1024
group_replication_consistency EVENTUAL
gtid_executed
gtid_executed_compression_period 1000
gtid_mode OFF_PERMISSIVE
gtid_next AUTOMATIC
gtid_owned
gtid_purged
have_compress YES
have_dynamic_loading YES
have_geometry YES
have_openssl YES
have_profiling YES
have_query_cache NO
have_rtree_keys YES
have_ssl YES
have_statement_timeout YES
histogram_generation_max_mem_size 20000000
host_cache_size 448
identity 0
immediate_server_version 999999
information_schema_stats_expiry 86400
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 4
innodb_buffer_pool_load_abort OFF
innodb_buffer_pool_load_at_startup ON
innodb_buffer_pool_load_now OFF
innodb_buffer_pool_size 3221225472
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_deadlock_detect ON
innodb_dedicated_server OFF
innodb_default_row_format dynamic
innodb_disable_sort_file_cache OFF
innodb_doublewrite ON
innodb_doublewrite_batch_size 16
innodb_doublewrite_files 2
innodb_doublewrite_pages 32
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 2
innodb_flush_method O_DIRECT
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 5
innodb_log_buffer_size 8388608
innodb_log_checksums ON
innodb_log_compressed_pages ON
innodb_log_file_size 268435456
innodb_log_files_in_group 2
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_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 4096
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 1
innodb_random_read_ahead OFF
innodb_read_ahead_threshold 56
innodb_read_io_threads 16
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_thread_concurrency 32
innodb_thread_sleep_delay 0
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 8.0.21
innodb_write_io_threads 16
insert_id 0
interactive_timeout 28800
internal_tmp_mem_storage_engine TempTable
join_buffer_size 262144
keep_files_on_create OFF
key_buffer_size 268435456
key_cache_age_threshold 300
key_cache_block_size 1024
key_cache_division_limit 100
keyring_operations ON
large_files_support ON
large_page_size 0
large_pages OFF
last_insert_id 0
lc_messages en_US
lc_time_names en_US
license GPL
local_infile ON
lock_wait_timeout 31536000
locked_in_memory OFF
log_bin ON
log_bin_basename /rdsdbdata/log/binlog/mysql-bin-changelog
log_bin_index /rdsdbdata/log/binlog/mysql-bin-changelog.index
log_bin_trust_function_creators OFF
log_bin_use_v1_row_events OFF
log_error /rdsdbdata/log/error/mysql-error.log
log_error_services log_filter_internal; log_sink_internal
log_error_suppression_list
log_error_verbosity 2
log_output TABLE
log_queries_not_using_indexes OFF
log_raw OFF
log_slave_updates ON
log_slow_admin_statements OFF
log_slow_extra OFF
log_slow_slave_statements OFF
log_statements_unsafe_for_binlog OFF
log_throttle_queries_not_using_indexes 0
log_timestamps UTC
long_query_time 5.000000
low_priority_updates OFF
lower_case_file_system OFF
lower_case_table_names 0
mandatory_roles
master_info_repository TABLE
master_verify_checksum OFF
max_allowed_packet 4194304
max_binlog_cache_size 18446744073709547520
max_binlog_size 134217728
max_binlog_stmt_cache_size 18446744073709547520
max_connect_errors 100
max_connections 320
max_delayed_threads 20
max_digest_length 1024
max_error_count 1024
max_execution_time 0
max_heap_table_size 134217728
max_insert_delayed_threads 20
max_join_size 18446744073709551615
max_length_for_sort_data 4096
max_points_in_geometry 65536
max_prepared_stmt_count 16382
max_relay_log_size 0
max_seeks_for_key 18446744073709551615
max_sort_length 1024
max_sp_recursion_depth 0
max_user_connections 0
max_write_lock_count 18446744073709551615
min_examined_row_limit 0
myisam_data_pointer_size 6
myisam_max_sort_file_size 9223372036853727232
myisam_mmap_size 18446744073709551615
myisam_recover_options OFF
myisam_repair_threads 1
myisam_sort_buffer_size 8388608
myisam_stats_method nulls_unequal
myisam_use_mmap OFF
mysql_native_password_proxy_users OFF
net_buffer_length 16384
net_read_timeout 30
net_retry_count 10
net_write_timeout 60
new OFF
ngram_token_size 2
offline_mode OFF
old OFF
old_alter_table OFF
open_files_limit 65535
optimizer_prune_level 1
optimizer_search_depth 62
optimizer_switch index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on,use_invisible_indexes=off,skip_scan=on,hash_join=on,subquery_to_derived=off,prefer_ordering_index=on
optimizer_trace enabled=off,one_line=off
optimizer_trace_features greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
optimizer_trace_limit 1
optimizer_trace_max_mem_size 1048576
optimizer_trace_offset -1
original_commit_timestamp 36028797018963968
original_server_version 999999
parser_max_mem_size 18446744073709551615
partial_revokes OFF
password_history 0
password_require_current OFF
password_reuse_interval 0
performance_schema ON
performance_schema_accounts_size -1
performance_schema_digests_size 10000
performance_schema_error_size 0
performance_schema_events_stages_history_long_size 10000
performance_schema_events_stages_history_size 10
performance_schema_events_statements_history_long_size 10000
performance_schema_events_statements_history_size 10
performance_schema_events_transactions_history_long_size 10000
performance_schema_events_transactions_history_size 10
performance_schema_events_waits_history_long_size 10000
performance_schema_events_waits_history_size 10
performance_schema_hosts_size -1
performance_schema_max_cond_classes 100
performance_schema_max_cond_instances -1
performance_schema_max_digest_length 1024
performance_schema_max_digest_sample_age 60
performance_schema_max_file_classes 80
performance_schema_max_file_handles 32768
performance_schema_max_file_instances -1
performance_schema_max_index_stat -1
performance_schema_max_memory_classes 450
performance_schema_max_metadata_locks -1
performance_schema_max_mutex_classes 300
performance_schema_max_mutex_instances -1
performance_schema_max_prepared_statements_instances -1
performance_schema_max_program_instances -1
performance_schema_max_rwlock_classes 60
performance_schema_max_rwlock_instances -1
performance_schema_max_socket_classes 10
performance_schema_max_socket_instances -1
performance_schema_max_sql_text_length 1024
performance_schema_max_stage_classes 175
performance_schema_max_statement_classes 218
performance_schema_max_statement_stack 10
performance_schema_max_table_handles -1
performance_schema_max_table_instances -1
performance_schema_max_table_lock_stat -1
performance_schema_max_thread_classes 100
performance_schema_max_thread_instances -1
performance_schema_session_connect_attrs_size 512
performance_schema_setup_actors_size -1
performance_schema_setup_objects_size -1
performance_schema_users_size -1
persist_only_admin_x509_subject
persisted_globals_load OFF
port 3306
preload_buffer_size 32768
print_identified_with_as_hex OFF
profiling OFF
profiling_history_size 15
protocol_compression_algorithms zlib,zstd,uncompressed
protocol_version 10
proxy_user
pseudo_slave_mode OFF
pseudo_thread_id 1164
query_alloc_block_size 8192
query_prealloc_size 8192
rand_seed1 0
rand_seed2 0
range_alloc_block_size 4096
range_optimizer_max_mem_size 8388608
rbr_exec_mode STRICT
read_buffer_size 1048576
read_only OFF
read_rnd_buffer_size 4194304
regexp_stack_limit 8000000
regexp_time_limit 32
relay_log /rdsdbdata/log/relaylog/relaylog
relay_log_basename /rdsdbdata/log/relaylog/relaylog
relay_log_index /rdsdbdata/log/relaylog/relaylog.index
relay_log_info_file relay-log.info
relay_log_info_repository TABLE
relay_log_purge ON
relay_log_recovery ON
relay_log_space_limit 0
report_host
report_password
report_port 3306
report_user
require_row_format OFF
require_secure_transport OFF
resultset_metadata FULL
rpl_read_size 8192
rpl_stop_slave_timeout 31536000
schema_definition_cache 256
secondary_engine_cost_threshold 100000.000000
secure_file_priv /tmp/
server_id 658899241
server_id_bits 32
server_uuid b2a6c6b9-d398-11e6-b6a4-12306f56ae16
session_track_gtids OFF
session_track_schema ON
session_track_state_change OFF
session_track_system_variables time_zone,autocommit,character_set_client,character_set_results,character_set_connection
session_track_transaction_info OFF
sha256_password_auto_generate_rsa_keys ON
sha256_password_private_key_path private_key.pem
sha256_password_proxy_users OFF
sha256_password_public_key_path public_key.pem
show_create_table_skip_secondary_engine OFF
show_create_table_verbosity OFF
show_old_temporals OFF
skip_external_locking ON
skip_name_resolve OFF
skip_networking OFF
skip_show_database OFF
slave_allow_batching OFF
slave_checkpoint_group 512
slave_checkpoint_period 300
slave_compressed_protocol OFF
slave_exec_mode IDEMPOTENT
slave_max_allowed_packet 1073741824
slave_net_timeout 60
slave_parallel_type DATABASE
slave_parallel_workers 0
slave_pending_jobs_size_max 134217728
slave_preserve_commit_order OFF
slave_rows_search_algorithms INDEX_SCAN,HASH_SCAN
slave_skip_errors OFF
slave_sql_verify_checksum ON
slave_transaction_retries 10
slave_type_conversions
slow_launch_time 2
slow_query_log ON
slow_query_log_file /rdsdbdata/log/slowquery/mysql-slowquery.log
socket /tmp/mysql.sock
sort_buffer_size 1048576
sql_auto_is_null OFF
sql_big_selects ON
sql_buffer_result OFF
sql_log_bin ON
sql_log_off OFF
sql_mode STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION
sql_notes ON
sql_quote_show_create ON
sql_require_primary_key OFF
sql_safe_updates OFF
sql_select_limit 20000
sql_slave_skip_counter 0
sql_warnings OFF
ssl_ca /rdsdbdata/rds-metadata/ca-cert.pem
ssl_capath
ssl_cert /rdsdbdata/rds-metadata/server-cert.pem
ssl_cipher ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA:AES128-SHA:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA:DHE-DSS-AES128-SHA:DHE-DSS-AES256-SHA
ssl_crl
ssl_crlpath
ssl_fips_mode OFF
ssl_key /rdsdbdata/rds-metadata/server-key.pem
stored_program_cache 256
stored_program_definition_cache 256
super_read_only OFF
sync_binlog 1
sync_master_info 10000
sync_relay_log 10000
sync_relay_log_info 10000
system_time_zone UTC
table_definition_cache 2000
table_encryption_privilege_check OFF
table_open_cache 4096
table_open_cache_instances 16
tablespace_definition_cache 256
temptable_max_ram 1073741824
temptable_use_mmap ON
thread_cache_size 11
thread_handling one-thread-per-connection
thread_stack 262144
time_zone UTC
timestamp 1610991021.519301
tls_ciphersuites
tls_version TLSv1,TLSv1.1,TLSv1.2,TLSv1.3
tmp_table_size 2097152
transaction_alloc_block_size 8192
transaction_allow_batching OFF
transaction_isolation REPEATABLE-READ
transaction_prealloc_size 4096
transaction_read_only OFF
transaction_write_set_extraction XXHASH64
unique_checks ON
updatable_views_with_limit YES
use_secondary_engine ON
version 8.0.21
version_comment Source distribution
version_compile_machine aarch64
version_compile_os Linux
version_compile_zlib 1.2.11
wait_timeout 28800
warning_count 0
windowing_use_high_precision ON
在此处显示状态等。 https://gist.github.com/DaveB93/138f6bac254fee5bbbbb7ce2af7c2fef
您计算的每线程内存使用量有误。这些变量（以及您未包含的 tmp_table_size ）并非同时使用。不要把它们加起来。即使你将它们加起来，至少有两个可能会被分配多次用于单个查询，所以你不能只是将它们相加。
基本上，MySQLTuner 计算的内存使用量完全是误导，您不应该相信它。我之前写过：What does "MySQL's maximum memory usage is dangerously high" mean by mysqltuner?
如果您想了解 实际 内存使用情况，请使用 PERFORMANCE_SCHEMA，或者在 SYS 架构中更容易阅读的视图。
PS 或 SYS 的文档非常密集，因此我会在像这样的博客中寻找更好的示例：
https://www.percona.com/blog/2020/11/02/understanding-mysql-memory-usage-with-performance-schema/