Mysql high cpu usage (over 600%) - mysql

Question

here is my mysql configuration file:
#
# 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
The server has 8core CPU and 22 GB of ram. Every day receives many requests from users, and recently a replication mechanism has been activated, with an implementation of a db master and a slave.
Now the server is really slow (on ssh top, mysqld reaches 600% and more of CPU Usage) and sometimes it go down of service. Please can you help me to fix this issue?

Answer 1

Rate Per Second=RPS
Suggestions to consider for your my.cnf [mysqld] section
thread_cache_size=100 # from 8 for multi-threading w 8 cores CAP at 100 per V 5.7
the following 4 are per CONNECTION RAM requests
sort_buffer_size=2M # from 1M to reduce sort_merge_passes
read_buffer_size=128K # from 1M to reduce handler_read_next RPS
read_rnd_buffer_size=256K # from ? may reduce handler_read_rnd_next RPS
join_buffer_size=128K # from 1M for join row pointers
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Answer 2

Rate Per Second=RPS Suggestions to consider for your my.cnf [mysqld] section
innodb_io_capacity=1500 # from 200 to enable higher RD & WD IOPS
read_rnd_buffer_size=192K # from 256K to reduce handler_read_rnd_next RPS
innodb_lru_scan_depth=100 # from 1024 for minimum to reduce CPU busy every SECOND
innodb_change_buffer_max_size=15 # from 25 percent since less than 1% used Del,Ins,Upd
innodb_flushing_avg_loops=5 # from 30 to reduce innodb_buffer_pool_pages_dirty
innodb_thread_concurrency=12 # from 6 to utilize more of your 8 core capacity
innodb_buffer_pool_dump_pct=90 # from 25 percent to warm more of BP on start of instance
Looking forward to Skype session with you in a few hours. Thanks, Wilson