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Re: MySQL 8 - terrible performance
Posted by: Hans Meiser
Date: February 14, 2019 03:33AM

Hello,

i tried changing innodb_flush_log_at_trx_commit, but there is no change.
with netdata i collected some charts during run of mysql_upgrade. there are only a few peaks in time, most of time there seems to be no activity.
https://ibb.co/YXLxwYw
last peak on right side marks end of mysql_upgrade process.

yes, initialization process happens only once, but if i notice this timeusage, iam afraid of having bad performance on production servers when running typical webapplications.
Can you confirm same behaviour and time difference when comparing this standardoperations with mysql 5.7 and 8.0 on same machine. can you confirm, that we see a regular behaviour at this point?

initialization process is one thing and i could live with it as a one time thing. But my benchmarks in first posting also dont look good. the benchmark shows bad performance with mysql8.0 just by running a lot selects. testdb is not optimized for mysql8, but i did not expect that timeusage and difference between 5.7 and 8.0

Another server - another test.
https://www.digitalocean.com/community/tutorials/how-to-measure-mysql-query-performance-with-mysqlslap
With mysql 5.7 i installed testdb and run mysqlslap.
result: 42.493 seconds

Now upgrade to mysql8.0 and rerun test with former installed db
result: 127.696 seconds

This reflects my fear: If we install/upgrade mysql8 on customer servers and typical webapps running slower then expected we will have much trouble with customers.

Thanks,
Hans

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