该服务器有 8 核 CPU 和 22 GB 内存。每天都会收到来自用户的大量请求，最近已激活复制机制，并实施了数据库主服务器和从服务器。现在服务器真的很慢（在 ssh top 上，mysqld 的 CPU 使用率达到 600% 甚至更高），有时会停止服务。请问您能帮我解决这个问题吗？
这是我的 mysql 配置文件：
#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
#
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
# Here is entries for some specific programs
# The following values assume you have at least 32M ram
[mysqld_safe]
socket = /var/run/mysqld/mysqld.sock
nice = 0
[mysqld]
#
# * Basic Settings
#
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
##
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
#bind-address = 127.0.0.1
#
# * Fine Tuning
#
innodb_buffer_pool_size = 12G
key_buffer_size = 1G
max_allowed_packet = 256M
thread_stack = 192K
thread_cache_size = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover-options = BACKUP
max_connections = 300
#innodb_buffer_pool_instances=8
#innodb_read_io_threads=8
#innodb_write_io_threads=8
#open_files_limit = 1024
#table_open_cache = 400
server_id = 2
bind-address = 0.0.0.0
log_bin = /var/log/mysql/mysql-bin.log
log_bin_index = /var/log/mysql/mysql-bin.log.index
relay_log = /var/log/mysql/mysql-relay-bin
relay_log_index = /var/log/mysql/mysql-relay-bin.index
expire_logs_days = 10
max_binlog_size = 100M
log_slave_updates = 1
auto-increment-increment = 2
auto-increment-offset = 2
replicate-ignore-db=phpmyadmin
replicate-ignore-db=mysql
skip-name-resolve
#table_cache = 64
#thread_concurrency = 10
#
# * Query Cache Configuration
#
query_cache_limit = 0
query_cache_size = 0
sort_buffer_size = 1M
join_buffer_size = 1M
read_buffer_size = 1M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file = /var/log/mysql/mysql.log
#general_log = 1
#
# Error log - should be very few entries.
#
log_error = /var/log/mysql/error.log
#
# Here you can see queries with especially long duration
#log_slow_queries = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
# other settings you may need to change.
#server-id = 1
#log_bin = /var/log/mysql/mysql-bin.log
expire_logs_days = 10
max_binlog_size = 100M
#binlog_do_db = include_database_name
#binlog_ignore_db = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem
答案1
对 my.cnf [mysqld] 部分更改的建议。
key_buffer_size=100M # from 1G for more reasonable RAM allocation
thread_cache_size=100 # from 8 to reduce threads_created
删除开头的 #
innodb_buffer_pool_instances for qty of 8 to minimize mutex contention
添加
innodb_lru_scan_depth=100 # from 1024 default to reduce CPU cycles used every SECOND
从 innodb_read_io_threads 中删除前 4 个 # 以及接下来的 3 个 # 以激活这些行
innodb_read_io_threads=64 # from 8 to encourage multi core processing
innodb_write_io_threads=64 # from 8 to encourage multi core processing
open_files_limit=4096 # from 1024 for now
table_open_cache=2048 # from 400 for now
join_buffer_size=128K # from 1M for more reasonable RAM per connection
read_buffer_size=128K # from 1M for more reasonable RAM per connection
最后一个将显著降低 handler_read_next 每秒的速率。