Bug #76894 print a warning if innodb-page-cleaners is set too high
Submitted: 30 Apr 2015 4:55
Reporter: Shane Bester (Platinum Quality Contributor) Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: InnoDB storage engine Severity:S4 (Feature request)
Version:5.7.7 OS:Any
Assigned to: CPU Architecture:Any
Tags: innodb_page_cleaners

[30 Apr 2015 4:55] Shane Bester
Description:
In srv0start.cc I'd like to see a warning in error log here:

if (srv_n_page_cleaners > srv_buf_pool_instances) {
/* limit of page_cleaner parallelizability
is number of buffer pool instances. */
srv_n_page_cleaners = srv_buf_pool_instances;
}

How to repeat:
start server with too high page cleaners:

--innodb-buffer-pool-size=10G --innodb-buffer-pool-instances=10 --innodb-page-cleaners=16 --log-error-verbosity=3

Then check error log for any indication the page cleaners value was changed.

select @@global.innodb_page_cleaners,
@@global.innodb_buffer_pool_instances,
@@global.innodb_buffer_pool_size,version()\G

*************************** 1. row ***************************
        @@global.innodb_page_cleaners: 10
@@global.innodb_buffer_pool_instances: 10
     @@global.innodb_buffer_pool_size: 10737418240