mysql - 数据库性能下降，升级到 MySQL 8.0.20 后

Question

将MySQL从5.7版本升级到8.0后，发现数据库性能明显下降。
升级 MySQL 前 CPU 使用率稳定在 30%+- 左右，但升级后 CPU 使用率变得不稳定并经常出现大峰值。
最近我测试了一些非常有趣的东西，我一直运行相同的查询几次，发现所用的持续时间变得越来越长。如下图所示。

我已经阅读了很多文章和堆栈溢出帖子，但没有一个解决方案是真正得到帮助的。
所以希望有人能和我分享一些关于调优MySQL8.0的想法或经验。
会很感激。
如果需要任何信息以进行进一步调查，请告诉我。
配置 my.ini:-

key_buffer_size = 2G
max_allowed_packet = 1M

;Added to reduce memory used (minimum is 400)
table_definition_cache = 600

sort_buffer_size = 4M
net_buffer_length = 8K
read_buffer_size = 2M
read_rnd_buffer_size = 2M
myisam_sort_buffer_size = 2G
;Path to mysql install directory
basedir="c:/wamp64/bin/mysql/mysql8.0.20"
log-error="c:/wamp64/logs/mysql.log"
;Verbosity Value  1 Errors only, 2  Errors and warnings , 3 Errors, warnings, and notes
log_error_verbosity=2
;Path to data directory
datadir="c:/wamp64/bin/mysql/mysql8.0.20/data"


;slow_query_log = ON
;slow_query_log_file = "c:/wamp64/logs/slow_query.log"

;Path to the language
;See Documentation:
; http://dev.mysql.com/doc/refman/5.7/en/error-message-language.html
lc-messages-dir="c:/wamp64/bin/mysql/mysql8.0.20/share"
lc-messages=en_US

; The default storage engine that will be used when create new tables
default-storage-engine=InnoDB
; New for MySQL 5.6 default_tmp_storage_engine if skip-innodb enable
; default_tmp_storage_engine=MYISAM

;To avoid warning messages
secure_file_priv="c:/wamp64/tmp"
skip-ssl

explicit_defaults_for_timestamp=true

; Set the SQL mode to strict
sql-mode=""
;sql-mode="STRICT_ALL_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_ZERO_DATE,NO_ZERO_IN_DATE,NO_AUTO_CREATE_USER"

;skip-networking

; Disable Federated by default
skip-federated

; Replication Master Server (default)
; binary logging is required for replication
;log-bin=mysql-bin

; binary logging format - mixed recommended
;binlog_format=mixed

; required unique id between 1 and 2^32 - 1
; defaults to 1 if master-host is not set
; but will not function as a master if omitted
server-id = 1

; Replication Slave (comment out master section to use this)

; New for MySQL 5.6 if no slave
skip-slave-start


; The InnoDB tablespace encryption feature relies on the keyring_file
; plugin for encryption key management, and the keyring_file plugin
; must be loaded prior to storage engine initialization to facilitate
; InnoDB recovery for encrypted tables. If you do not want to load the
; keyring_file plugin at server startup, specify an empty string.
early-plugin-load=""

;innodb_data_home_dir = C:/mysql/data/
innodb_data_file_path = ibdata1:12M:autoextend
;innodb_log_group_home_dir = C:/mysql/data/
;innodb_log_arch_dir = C:/mysql/data/

; You can set .._buffer_pool_size up to 50 - 80 %
; of RAM but beware of setting memory usage too high
innodb_buffer_pool_size = 4G

; Set .._log_file_size to 25 % of buffer pool size
innodb_log_file_size = 16M
innodb_log_buffer_size = 8M
innodb_thread_concurrency = 64
innodb_flush_log_at_trx_commit = 2

log_bin_trust_function_creators = 1;

innodb_lock_wait_timeout = 120
innodb_flush_method=normal
innodb_use_native_aio = true

innodb_flush_neighbors = 2
innodb_autoinc_lock_mode = 1

[mysqldump]
quick
max_allowed_packet = 16M

[mysql]
no-auto-rehash
; Remove the next comment character if you are not familiar with SQL
;safe-updates

[isamchk]
key_buffer_size = 20M
sort_buffer_size = 20M
read_buffer_size = 2M
write_buffer_size = 2M

[myisamchk]
key_buffer_size = 256M ;20M hys
sort_buffer_size_size = 20M
read_buffer_size = 2M
write_buffer_size = 2M

[mysqlhotcopy]
interactive-timeout

[mysqld]
port = 3306
skip-log-bin
default_authentication_plugin= mysql_native_password

max_connections = 400
max_connect_errors = 100000

innodb_read_io_threads = 32
innodb_write_io_threads = 8
innodb_thread_concurrency = 64

硬件:-
内存:16GB
CPU:4 核 3.0 Ghz
显示全局状态:
https://pastebin.com/FVZrgnTw
显示引擎 INNODB 状态:
https://pastebin.com/Rewp84Gi
显示全局变量:
https://pastebin.com/3v6cM6KZ

Answer 1

每秒速率 = RPS
为 my.ini [mysqld] 部分考虑的建议
在 my.ini 配置中有超过 1 个 [mysqld] 部分是不寻常的
您在 my.ini 末尾附近的部分可以移到之前
[mysqldump] 避免混淆。

innodb_lru_scan_depth=100  # from 1024 to conserve 90% of CPU cycles used for function
key_buffer_size=16M  # from 1G to conserve RAM - you are not using MyISAM data tables
read_rnd_buffer_size=64K  # from 2M to reduce handler_read_rnd_next RPS of 1,872,921
innodb_io_capacity=900  # from 200 to more of your rotating drive IOPS capacity

您应该会发现查询完成时间和 CPU 繁忙度随着这些更改而减少。
select_scan 平均 41 RPS，是由于索引不可用导致延迟。
如需其他建议，请查看配置文件、联系信息的网络配置文件、常见问题解答、其他提示和可免费下载的实用程序脚本，以帮助进行性能调整。