Bug #81611 Add P_S metrics to collect compressed page bytes vs other types written to relog
Submitted: 26 May 2016 11:13 Modified: 25 Aug 2016 10:51
Reporter: Simon Mudd (OCA) Email Updates:
Status: Verified Impact on me:
Category:MySQL Server: Performance Schema Severity:S4 (Feature request)
Version:5.7 OS:Any
Assigned to: Marc ALFF CPU Architecture:Any
Tags: performance_schema

[26 May 2016 11:13] Simon Mudd
See bug#81610.

It looks like it's not possible at the moment to see the number of bytes written to the redo logs which come from compressed pages compared to the total.  If the percentage is high and I/O levels are high then it would be useful potentially to turn off this setting as it should be safe.  Currently I believe that there are no innodb or P_S metrics which provide that information.

How to repeat:
see above.

Suggested fix:
Provide some InnoDB or P_S metrics to track this, so that we can measure the impact in reduced i/o should the ratio of compressed writes to the total be high. That would make it easier for us to see the effect of turning off the the writes by setting innodb_log_compressed_pages=off.

I guess we can just do this and look at the i/o profile and see how it changes but it would be handy to see if the change is actually going to make a difference prior to doing that and the extra metrics would provide that information.