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Re: MySQL 8 - terrible performance
Posted by: Hans Meiser
Date: February 13, 2019 03:36AM

Hello,

yes this is true. But its doesn't matter if i do an upgrade from 5.7 to 8.0 or reinitialise a fresh 8.0 installation. result in both cases is the same.

OS is Ubuntu 18.04
To compare i measured time of same operations on same server with different MySQL Versions.

First server is an average system: 4G/AMD Athlon(tm) 7750 Dual-Core Processor/HDD
mysql was stopped, deleted all data in /var/lib/mysql and run command "mysqld --initialize-insecure --console" after that command i run "mysql_upgrade -s --force" several times.

In both mysql-Versions binlogging is enabled.

tests with mysql 5.7.25

mysqld --initialize-insecure --console
real 0m27,929s
mysql_upgrade -s --force
real 0m48,751s
real 0m32,481s
real 0m33,115s

After that i removed all mysql, installed mysql 8.0.15 and did same procedure with deleting all data, reinitialise and run mysql_upgrade
this is result with mysql 8.0.15
mysqld --initialize-insecure --console
real 1m4,912
mysql_upgrade -s --force
real 10m16,397s
real 9m47,756s
real 9m56,170s

If i activate general-log, i can read inserts line by line ;) . System has only minimal cpu and io-usage during mysql_upgrade. Seems that MySQl is not using full system power.

To compare i used an better server with 48G/Intel(R) Xeon(R) CPU E5645 @ 2.40GHz/SSD

mysql 5.7.25
mysqld --initialize-insecure --console
real 0m2,385s
mysql_upgrade -s --force
real 0m0,956s
real 0m0,901s
real 0m0,855s


mysql 8.0
mysqld --initialize-insecure --console
real 0m5,028s

mysql_upgrade -s --force
real 0m9,673s
real 0m9,503s
real 0m9,381s

You see on better server times are in total better, but we see same time-factor between 5.7 and 8.0


Here is a output of "mysqladmin variables" with current values. we adjust only a few of variables, most of them are default. I cant believe that default variables have that negative influence.
https://pastebin.com/v37DMrQc

Thanks you for your help. I hope you see something odd in my config or can tell advice to better situation. Iam afraid of having bad performance on production servers.

Thanks,
Hans

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