I encountered the same issue (and created a duplicate because I did not found this issue first )
Anyway, if it can help the troubleshooting I have flamegraph of Percona and MySQL running the same workload of SELECT ... FOR UPDATE queries available here:
Aaditya Dubey
October 9, 2023 at 11:56 AM
Hi ,
Thank you for the report and feedback. Verified as described:
Only Percona server is impacted by this, sending the concern to engineering for further review and updates.
Medium
Executing SELECT ... FOR UPDATE statement, causes high CPU spikes (it does not matter, whether table is empty or there are any rows.)
Sample table:
Query:
It causes ongoing 100% CPU usage, when query is executed in interval (e.g. every 1s).
Naive bash script for bug reproduction:
I have tested with following docker images (with default configuration):
Docker Image
High CPU
mysql:5.7
NO
mysql:8.0
NO
mariadb:10
NO
percona:5.7
NO
percona:8.0.12-2rc1
NO
percona:8.0.20-11
NO
percona:8.0.21-12
YES
percona:8.0.22-13
YES
percona:8.0.29-21
YES
percona:8.0.32-24
YES
percona:8.0.33-25
YES
It looks like, the performance degradation was introduced in percona 8.0.21-12.
Attachment
percona-high-cpu-select-for-update.tar.gzcontains docker-compose with mentioned database setup and bash script.Related Issues: