[MDEV-13019] scrub log cause high system load Created: 2017-06-07  Updated: 2020-03-04  Resolved: 2017-08-07

Status: Closed
Project: MariaDB Server
Component/s: Storage Engine - InnoDB
Affects Version/s: 10.2.6
Fix Version/s: N/A

Type: Bug Priority: Major
Reporter: Michael Xu Assignee: Unassigned
Resolution: Incomplete Votes: 0
Labels: need_feedback
Environment:

CentOS 7.x x86_64

Issue Links:
Relates
relates to MDEV-21870 Deprecate and ignore innodb_scrub_log... Closed

 Description   

The server is a brand new, dedicated mysql box, and here are the relevant variables in my.cnf

innodb_encryption_threads = 8
innodb_background_scrub_data_check_interval = 3600
innodb_background_scrub_data_compressed = 1
innodb_background_scrub_data_interval = 86400
innodb_background_scrub_data_uncompressed = 1
innodb_immediate_scrub_data_uncompressed = 1
innodb_scrub_log = 1
innodb_scrub_log_speed = 50000

After the service restarted, the total CPU usage is 0, and after a short while(several minutes, an hour, not quite sure), the total CPU usage grows to 15, and system load is up to 8. And after I comment the above variables, the system is back to normal.

Is there anything wrong with my configuration?

perf top -p ${pid}
Samples: 1M of event 'cycles:ppp', Event count (approx.): 278084696592
Overhead Shared Object Symbol
30.93% mysqld [.] fil_crypt_thread
29.82% mysqld [.] ut_delay
16.56% [kernel] [k] _raw_spin_lock
1.41% mysqld [.] PolicyMutex<TTASEventMutex<GenericPolicy> >::enter

 Comments   
Comment by Elena Stepanova [ 2017-06-10 ]

Could you please attach the whole config file(s)?

Comment by Elena Stepanova [ 2017-07-09 ]

Also, when the CPU usage grows, does it become permanent, or does it raise and after a whole goes back to normal, and then the cycle repeats?
And when you are saying it's a brand new server, does it mean that the database is empty, there are no InnoDB users' tables, and there is no significant activity on the server before the spikes start happening?

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