我的 MySQL 伺服器正在消耗大量記憶體。

記憶體佔用1.記憶體消耗降序排列（前4位）

特別是 MySQL 的記憶體消耗 -

為什麼會有這麼多mysqld程序？他們是程序/執行緒嗎？它們正在消耗大量記憶體。我在某個地方設置了那個數字嗎？

此外，我的查詢需要很長時間才能執行，因此我的網站變慢了。

我的 my.cnf 的一個片段 -

[mysqld]
key_buffer      = 16M
max_allowed_packet  = 16M
thread_stack        = 192K
thread_cache_size       = 8
myisam-recover         = BACKUP
query_cache_limit   = 1M
query_cache_size        = 16M

innodb_lock_wait_timeout = 120
innodb_buffer_pool_size = 500M

[mysqldump]
max_allowed_packet  = 16M

[mysql]
#no-auto-rehash # faster start of mysql but no tab completition

[isamchk]
key_buffer      = 16M
wait_timeout        = 60

我跑去tuning-primer.sh檢查我做錯了什麼。結果的相關部分tuning-primer.sh-

MySQL Version 5.1.63-0ubuntu0.10.04.1 i486

Uptime = 176 days 0 hrs 24 min 31 sec
Avg. qps = 8
Total Questions = 128972512
Threads Connected = 6

SLOW QUERIES
The slow query log is NOT enabled.
Current long_query_time = 10.000000 sec.
You have 55628 out of 128972533 that take longer than 10.000000 sec. to complete
Your long_query_time seems to be fine

BINARY UPDATE LOG
The binary update log is NOT enabled.
You will not be able to do point in time recovery
See http://dev.mysql.com/doc/refman/5.1/en/point-in-time-recovery.html

WORKER THREADS
Current thread_cache_size = 8
Current threads_cached = 7
Current threads_per_sec = 0
Historic threads_per_sec = 0
Your thread_cache_size is fine

MAX CONNECTIONS
Current max_connections = 151
Current threads_connected = 5
Historic max_used_connections = 147
The number of used connections is 97% of the configured maximum.
You should raise max_connections

INNODB STATUS
Current InnoDB index space = 109 M
Current InnoDB data space = 10.32 G
Current InnoDB buffer pool free = 0 %
Current innodb_buffer_pool_size = 500 M
Depending on how much space your innodb indexes take up it may be safe
to increase this value to up to 2 / 3 of total system memory

MEMORY USAGE
Max Memory Ever Allocated : 929 M
Configured Max Per-thread Buffers : 405 M
Configured Max Global Buffers : 534 M
Configured Max Memory Limit : 939 M
Physical Memory : 3.94 G
Max memory limit seem to be within acceptable norms

KEY BUFFER
Current MyISAM index space = 1 M
Current key_buffer_size = 16 M
Key cache miss rate is 1 : 204
Key buffer free ratio = 88 %
Your key_buffer_size seems to be fine

QUERY CACHE
Query cache is enabled
Current query_cache_size = 16 M
Current query_cache_used = 8 M
Current query_cache_limit = 1 M
Current Query cache Memory fill ratio = 50.29 %
Current query_cache_min_res_unit = 4 K
MySQL won't cache query results that are larger than query_cache_limit in size

SORT OPERATIONS
Current sort_buffer_size = 2 M
Current read_rnd_buffer_size = 256 K
Sort buffer seems to be fine

JOINS
Current join_buffer_size = 132.00 K
You have had 10728 queries where a join could not use an index properly
You should enable "log-queries-not-using-indexes"
Then look for non indexed joins in the slow query log.
If you are unable to optimize your queries you may want to increase your
join_buffer_size to accommodate larger joins in one pass.

Note! This script will still suggest raising the join_buffer_size when
ANY joins not using indexes are found.

OPEN FILES LIMIT
Current open_files_limit = 1024 files
The open_files_limit should typically be set to at least 2x-3x
that of table_cache if you have heavy MyISAM usage.
Your open_files_limit value seems to be fine

TABLE CACHE
Current table_open_cache = 64 tables
Current table_definition_cache = 256 tables
You have a total of 130 tables
You have 64 open tables.
Current table_cache hit rate is 0%
, while 100% of your table cache is in use
You should probably increase your table_cache

TEMP TABLES
Current max_heap_table_size = 16 M
Current tmp_table_size = 16 M
Of 6404640 temp tables, 48% were created on disk
Perhaps you should increase your tmp_table_size and/or max_heap_table_size
to reduce the number of disk-based temporary tables
Note! BLOB and TEXT columns are not allow in memory tables.
If you are using these columns raising these values might not impact your 
ratio of on disk temp tables.

TABLE SCANS
Current read_buffer_size = 128 K
Current table scan ratio = 206 : 1
read_buffer_size seems to be fine

TABLE LOCKING
Current Lock Wait ratio = 1 : 84225
Your table locking seems to be fine

我的伺服器規格 -

Disk Size   80GB ( Used = 50GB )
RAM         4GB
Swap    4GB
Number of CPUs  8
OS type 32 bit
OS  Ubuntu 10.04

為什麼有這麼多執行緒

我以前見過很多次。這不是問題。它只是表示如何安裝 mysqld 二進製文件。我之前討論過這個：見我的 2012 年 3 月 29 日的文章：相同的 mysql 程序

舊的原始碼編譯版本的 mysqld 將產生多個執行緒。我不知道什麼設置可以避免這種情況。我通常喜歡安裝 RPM 版本而不是 yum 安裝或進行原始碼編譯。

或者，您可以升級到最新版本。您還可以查找 MySQL 5.1.63 的 RPM 版本並安裝它。否則，您無需擔心任何事情。

由於數據庫連接是執行緒，因此您可以根據需要將max_connections設置為高或低來更改連接數。例如，您可以使用以下方法即時設置它：

SET GLOBAL max_connections = 500;

當然，您必須將該設置添加到每次重新啟動 mysqld 時保持 500 /etc/my.cnf。max_connections

您的原始問題

要查找哪些查詢需要很長時間，您可以使用pt-query-digest動態執行此操作。以下是我關於如何設置的 DBA StackExchange 文章：

• Jun 26, 2012:現在正在執行什麼？
• Apr 24, 2012:調查 MySQL 吞吐量的峰值
• Nov 24, 2011: MySQL 一般查詢日誌性能影響

試試看 ！！！

引用自：https://serverfault.com/questions/555693