MySQL Bugs: #76309: Log a warning if timer

Bug #76309	Log a warning if timer_overhead is huge
Submitted:	13 Mar 2015 7:51	Modified:	20 Nov 2015 10:06
Reporter:	Daniël van Eeden (OCA)	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: Performance Schema	Severity:	S4 (Feature request)
Version:	5.6	OS:	Any
Assigned to:		CPU Architecture:	Any

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Description:
I've seen some situations where the TIMER_OVERHEAD column from the performance_schema.performance_timers table for the CYCLE timer had a unexpectedly high number.

This can cause a high performance_schema overhead.

How to repeat:
See description

Suggested fix:
Log a warning to the error log if the overhead for the CYCLE timer is more than 200.

This was observed with RHEL on VMWare ESXi. If I recall it correctly the processor was an Intel Xeon in a HP blade.