MySql最大内存危险高仍然要求增加

Question

我有一个非常轻的流量Wordpress站点在一个虚拟机上有4个内核/ 8GB内存。我注意到，通过运行mysqltuner.pl脚本，有时通过查询网站的查询速度非常缓慢。下面是结果：

[OK] Currently running supported MySQL version 10.1.22-MariaDB 
[OK] Operating on 64-bit architecture 

-------- Log file Recommendations ------------------------------------------------------------------ 
[--] Log file: ./master_error.log(1M) 
[OK] Log file ./master_error.log exists 
[OK] Log file ./master_error.log is readable. 
[OK] Log file ./master_error.log is not empty 
[OK] Log file ./master_error.log is smaller than 32 Mb 
[!!] ./master_error.log contains 89 warning(s). 
[!!] ./master_error.log contains 24 error(s). 
[--] 4 start(s) detected in ./master_error.log 
[--] 1) 2017-03-24 3:43:22 140281079671040 [Note] /usr/sbin/mysqld: ready for connections. 
[--] 2) 2017-03-24 3:41:30 140390495832320 [Note] /usr/sbin/mysqld: ready for connections. 
[--] 3) 2017-03-24 3:37:36 139677438822656 [Note] /usr/sbin/mysqld: ready for connections. 
[--] 4) 2017-03-03 11:45:32 139685722654976 [Note] /usr/sbin/mysqld: ready for connections. 
[--] 3 shutdown(s) detected in ./master_error.log 
[--] 1) 2017-03-24 3:42:18 140390132259584 [Note] /usr/sbin/mysqld: Shutdown complete 
[--] 2) 2017-03-24 3:40:01 139677360564992 [Note] /usr/sbin/mysqld: Shutdown complete 
[--] 3) 2017-03-24 3:37:32 139685358557952 [Note] /usr/sbin/mysqld: Shutdown complete 

-------- Storage Engine Statistics ----------------------------------------------------------------- 
[--] Status: +Aria +CSV +InnoDB +MEMORY +MRG_MyISAM +MyISAM +PERFORMANCE_SCHEMA +SEQUENCE 
[--] Data in InnoDB tables: 277M (Tables: 677) 
[OK] Total fragmented tables: 0 

-------- Security Recommendations ------------------------------------------------------------------ 
[OK] There are no anonymous accounts for any database users 
[OK] All database users have passwords assigned 
[!!] There is no basic password file list! 

-------- CVE Security Recommendations -------------------------------------------------------------- 
[--] Skipped due to --cvefile option undefined 

-------- Performance Metrics ----------------------------------------------------------------------- 
[--] Up for: 13d 11h 25m 55s (3M q [2.764 qps], 43K conn, TX: 20G, RX: 451M) 
[--] Reads/Writes: 97%/3% 
[--] Binary logging is disabled 
[--] Physical Memory  : 7.6G 
[--] Max MySQL memory : 24.3G 
[--] Other process memory: 2.3G 
[--] Total buffers: 22.5G global + 12.5M per thread (151 max threads) 
[--] P_S Max memory usage: 0B 
[--] Galera GCache Max memory usage: 0B 
[!!] Maximum reached memory usage: 22.7G (296.63% of installed RAM) 
[!!] Maximum possible memory usage: 24.3G (318.26% of installed RAM) 
[!!] Overall possible memory usage with other process exceeded memory 
[OK] Slow queries: 0% (11K/3M) 
[OK] Highest usage of available connections: 10% (16/151) 
[OK] Aborted connections: 0.00% (2/43596) 
[--] Skipped name resolution test due to skip_networking=ON in system variables. 
[!!] Query cache may be disabled by default due to mutex contention. 
[OK] Query cache efficiency: 40.2% (1M cached/4M selects) 
[OK] Query cache prunes per day: 0 
[OK] Sorts requiring temporary tables: 0% (7 temp sorts/71K sorts) 
[OK] No joins without indexes 
[!!] Temporary tables created on disk: 51% (44K on disk/86K total) 
[OK] Thread cache hit rate: 99% (23 created/43K connections) 
[OK] Table cache hit rate: 22% (854 open/3K opened) 
[OK] Open file limit used: 0% (60/16K) 
[OK] Table locks acquired immediately: 100% (1M immediate/1M locks) 

-------- Performance schema ------------------------------------------------------------------------ 
[--] Performance schema is disabled. 
[--] Memory used by P_S: 0B 
[--] Sys schema isn't installed. 

-------- ThreadPool Metrics ------------------------------------------------------------------------ 
[--] ThreadPool stat is enabled. 
[--] Thread Pool Size: 4 thread(s). 
[--] Using default value is good enough for your version (10.1.22-MariaDB) 

-------- MyISAM Metrics ---------------------------------------------------------------------------- 
[!!] Key buffer used: 18.9% (2B used/11B cache) 
[OK] Key buffer size/total MyISAM indexes: 11.0G/123.0K 
[OK] Read Key buffer hit rate: 99.3% (1K cached/9 reads) 
[OK] Write Key buffer hit rate: 100.0% (60 cached/60 writes) 

-------- InnoDB Metrics ---------------------------------------------------------------------------- 
[--] InnoDB is enabled. 
[--] InnoDB Thread Concurrency: 0 
[OK] InnoDB File per table is activated 
[OK] InnoDB buffer pool/data size: 11.0G/278.0M 
[!!] Ratio InnoDB log file size/InnoDB Buffer pool size (1.77556818181818 %): 100.0M * 2/11.0G should be equal 25% 
[!!] InnoDB buffer pool instances: 8 
[--] InnoDB Buffer Pool Chunk Size not used or defined in your version 
[OK] InnoDB Read buffer efficiency: 100.00% (111655571 hits/ 111658256 total) 
[OK] InnoDB Write log efficiency: 97.88% (1070445 hits/ 1093608 total) 
[OK] InnoDB log waits: 0.00% (0 waits/23163 writes) 

-------- AriaDB Metrics ---------------------------------------------------------------------------- 
[--] AriaDB is enabled. 
[OK] Aria pagecache size/total Aria indexes: 128.0M/1B 
[OK] Aria pagecache hit rate: 97.3% (1M cached/35K reads) 

-------- TokuDB Metrics ---------------------------------------------------------------------------- 
[--] TokuDB is disabled. 

-------- XtraDB Metrics ---------------------------------------------------------------------------- 
[--] XtraDB is disabled. 

-------- RocksDB Metrics --------------------------------------------------------------------------- 
[--] RocksDB is disabled. 

-------- Spider Metrics ---------------------------------------------------------------------------- 
[--] Spider is disabled. 

-------- Connect Metrics --------------------------------------------------------------------------- 
[--] Connect is disabled. 

-------- Galera Metrics ---------------------------------------------------------------------------- 
[--] Galera is disabled. 

-------- Replication Metrics ----------------------------------------------------------------------- 
[--] Galera Synchronous replication: NO 
[--] No replication slave(s) for this server. 
[--] This is a standalone server. 

-------- Recommendations --------------------------------------------------------------------------- 
General recommendations: 
Control warning line(s) into ./master_error.log file 
Control error line(s) into ./master_error.log file 
Reduce your overall MySQL memory footprint for system stability 
Dedicate this server to your database for highest performance. 
When making adjustments, make tmp_table_size/max_heap_table_size equal 
Reduce your SELECT DISTINCT queries which have no LIMIT clause 
Performance should be activated for better diagnostics 
Consider installing Sys schema from https://github.com/mysql/mysql-sys 
Variables to adjust: 
    *** MySQL's maximum memory usage is dangerously high *** 
    *** Add RAM before increasing MySQL buffer variables *** 
    query_cache_type (=0) 
    tmp_table_size (> 64M) 
    max_heap_table_size (> 64M) 
    performance_schema = ON enable PFS 
    innodb_log_file_size * innodb_log_files_in_group should be equals to 1/4 of buffer pool size (=5G) if possible. 
    innodb_buffer_pool_instances(=11) 

...这是我为server.conf：

[mysql] 
no-auto-rehash 

[myisamchk] 
key_buffer_size = 256M 
sort_buffer_size = 256M 
read_buffer = 2M 
write_buffer = 2M 

[mysqlhotcopy] 
interactive-timeout 

[mysqld] 
# Connection and Thread variables 
socket = /var/lib/mysql/mysql.sock 
pid-file=/var/lib/mysql/maria.pid 
tmpdir = /run/mariadb 
optimizer_search_depth=0 
bind-address = 127.0.0.1 

skip-external-locking 
key_buffer_size = 11G 
max_allowed_packet = 1M 
table_open_cache = 4000 
sort_buffer_size = 2M 
read_buffer_size = 2M 
read_rnd_buffer_size = 8M 
myisam_sort_buffer_size = 64M 
thread_cache_size = 8 
query_cache_size = 256M 
query_cache_limit = 4M 
tmp_table_size = 64M 
max_heap_table_size = 64M 

# Try number of CPU's*2 for thread_concurrency 
thread_concurrency = 2 

innodb_data_home_dir = /var/lib/mysql 
innodb_data_file_path = ibdata1:10M:autoextend 
innodb_log_group_home_dir = /var/lib/mysql 
innodb_buffer_pool_size = 11G 
innodb_additional_mem_pool_size = 20M 
innodb_log_file_size = 100M 
innodb_log_buffer_size = 8M 
innodb_flush_log_at_trx_commit = 0 
innodb_lock_wait_timeout = 50 

innodb_thread_concurrency = 0 
innodb_read_io_threads = 64 
innodb_write_io_threads = 64 


# Security variables 
local_infile     = 0 
secure_auth     = 1 
sql_mode      = TRADITIONAL,NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES 
skip_name_resolve    = 1 
symbolic-links=0 
skip-networking 

### LOGS ### 
# MySQL error log 
log_error      = master_error.log 
log_warnings     = 2 
# innodb_print_all_deadlocks  = 1 

# Slow Query Log 
slow_query_log_file   = master_slow.log 
slow_query_log     = 1 
log_queries_not_using_indexes = 1 
long_query_time    = 0.5 
min_examined_row_limit   = 100 

# General Query Log 
general_log_file    = master_general.log 
general_log     = 0 

[mysqldump] 
quick 
max_allowed_packet = 16M 

有些事情似乎显然是错误的，如为4000的table_open_cache，但我想看看一些专家在我开始摆弄设置之前有一些建议。同样困惑的是，如何有如此高的内存使用量，但仍然是进一步提高价值的建议。

Answer 1

mysqltuner不够完美。但你做有一些设置，对于8GB的RAM真的太高...

8GB的RAM，基本上没有MyISAM表？ key_buffer_size应该更像20M，不是11G！如果mysqltuner人们正在倾听，他们应该修复该测试。

另外，innodb_buffer_pool_size应该只有5G，避免吹出RAM！ （并且将innodb_buffer_pool_instances更改为5.）

query_cache_size在大约50M以上变得低效。

log_queries_not_using_indexes不必要地混淆缓慢日志;把它关掉。

咏叹调 - 是1B一个字节还是一个十亿字节？ （mysqltuner的另一个bug）。

由于您有超额分配给MySQL的内存，它可能会交换。因为它假定所有的缓冲区都是RAM驻留的，所以交换是对于MySQL来说效率低下的。