我的服务器 mysql 出了大问题。一切运行正常，但从上周开始，它变得非常慢。每个查询都很慢（有时超过 20 秒）。我没有更改任何配置。
有人能帮我知道为什么我的服务器现在很慢吗？
谢谢。
这是我的my.cnf：
[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
language = /usr/share/mysql/english
#join_buffer_size = 128.0K
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
#
key_buffer = 16M
max_allowed_packet = 16M
max_heap_table_size = 64M
tmp_table_size = 64M
thread_stack = 128K
thread_cache_size = 8
#max_connections = 100
table_cache = 400
join_buffer_size = 2000K
#thread_concurrency = 10
#
# * Query Cache Configuration
#
query_cache_limit = 1M
query_cache_size = 16M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
#log = /var/log/mysql/mysql.log
#
# Error logging goes to syslog. This is a Debian improvement :)
#
# 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.
#server-id = 1
log_bin = /var/log/mysql/mysql-bin.log
# WARNING: Using expire_logs_days without bin_log crashes the server! See README.Debian!
expire_logs_days = 10
max_binlog_size = 100M
#binlog_do_db = include_database_name
#binlog_ignore_db = include_database_name
#
# * BerkeleyDB
#
# Using BerkeleyDB is now discouraged as its support will cease in 5.1.12.
skip-bdb
#
# * 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!
# You might want to disable InnoDB to shrink the mysqld process by circa 100MB.
#skip-innodb
innodb_buffer_pool_size = 42M
#
# * 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
[mysqldump]
quick
quote-names
max_allowed_packet = 16M
[mysql]
#no-auto-rehash # faster start of mysql but no tab completition
[isamchk]
key_buffer = 16M
答案1
你应该避免thread_stack选项在您的配置中。虽然此选项不会影响性能，但可能会导致问题。
这文章可能会有用。
答案2
如果不确切了解您的工作量，那就不行。
我建议您在非生产服务器上重现该问题，然后您可以安全地尝试修复它。
您的服务器针对少量内存进行了调整。如果您的数据库比玩具还大，这可能会导致性能不佳。
我假设您的服务器专用于作为数据库；您想要将相当多的 RAM 分配给 innodb_buffer_pool 或 key_buffer，这取决于您的应用程序使用的是 innodb 还是 myisam。
您应该了解开发人员正在使用什么，并让他们给您提供调整技巧。
由于数据越来越大，您的数据库性能可能会下降；大多数数据库都会发生这种情况，因此您需要联系您的开发团队并让他们阻止这种情况发生，或者进行容量规划，以便您能够处理未来的增长。
答案3
这是 VPS 吗？尝试启用 innodb 中的延迟提交，
innodb_flush_log_at_trx_commit = 2
这并不安全，但你可以在 io 负载较大的情况下尝试它。
在此处粘贴 vmstat 1 的输出
答案4
尝试关闭“log_slow_queries”，这会很快填满日志文件并消耗日志资源。
还可以尝试通过参数“log-queries-not-using-indexes”找出哪些查询可能因为没有使用索引而变得缓慢（请参阅mysql 手册）。
您可以使用“EXPLAIN选择...“以便您的查询找出哪些不使用索引或哪些索引可以改进。警告：不要使用太多索引，因为在 INSERT 和 UPDATE（当然还有 DELETE）上它们也必须更新。
CU，阿内普