20150110 my sql-performanceschema
TRANSCRIPT
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Troubleshooting with MySQL Performance Schema Ivan Ma 2015-01-10
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MySQL : Agenda
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Why and What – Performance Schema
Performance Schema Tables
Using MySQL Workbench
Try and See !
Questions
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Why Performance Schema?
System Low throughput?
?
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DBA
Hot table?
Network
High traffic on link?
Storage
Too much disk spin? App Developer
Slow application?
MySQL Developer
Code contention?
End User
Stuck session?
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What is Performance Schema
• The MySQL Performance Schema is a feature for monitoring MySQL Server execution at a low level.
– to inspect internal execution of the server at runtime. (Data Collection by Instrumentation at code level. No separate threads.)
– implemented using the PERFORMANCE_SCHEMA storage engine
– to monitor server events. An “event” is anything the server does that takes time and has been instrumented so that timing information can be collected.
• Tables in the performance_schema database are views or temporary tables that use no persistent on-disk storage.
• No memory allocation is done beyond that which occurs during server startup
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The Journey : Then and now..
• MySQL 5.5 (1st Release P_S)
• Only waits events
– Mutex waits
– Conditions waits
– R/W locks waits
– File I/O waits
• Setup_(timers/consumers/instruments) tables
• Few summary tables
• 17 Tables and 218 Instruments
• MySQL 5.6
• Statements and stages
• Table, Index and network I/O. Table locks
• Host Cache
• User, account, host
• Setup_(actor/objects)
• Multiple summary tables
• Events’ hierarchy
• 52 Tables and 550 Instruments
• MySQL 5.7 (DMRs)
• Instrumentation:
– Transactions
– Metadata locks
– Prepared statements
– Stored programs
– Memory usage
• User variables
• Replication summary tables
• 76 Tables and 885 Instruments
• … 6
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MySQL performance_schema Database
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MySQL 5.6 Performance Schema Tables
• setup_% tables
• event_% tables
– Category • stage
• statement
• wait
– Type • current
• history
• Summary Tables
• Instances tables
• Connection tables
• Misc Tables
– host cache table
– performance timers
– threads
– users
– session*attrs
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Some notes with Using MySQL Workbench
• Default SQL Editor with MySQL Workbench is using ‘Safe update mode’
– Edit Perference
• Why care –
– With Performance Schema, No KEY
– Update setup_% tables may not have ‘key’ on where clause
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Performance Schema Options …(1)
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Performance Schema Options …(2)
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Performance Schema Options …(3)
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Default P_S setup_consumer
• Only a few instrumentation is ON
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setup_actor
• (HOST, USER, ROLE) default with (‘%’, ‘%’, ’%’)
• All foreground threads are monitored.
• Update to this table has no change to existing started threads.
• Demo
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Summary Tables
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Getting statements summary by account (e.g. ‘tpcc’)
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Why the SQL takes so long to run …
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At this moments
• We see
– How we can enable Performance Schema
– What to see (enable what you want to see to reduce the overhead) • e.g. Only the session with the user login
– Statement taking too long to run
• What about “Wait Time”, “IO Time”, “Thread”, “Internal Stages”
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A Better way to look at this by using sys schema
• Using MySQL Workbench
– The first time clicking the Performance Schema Setup Install SYS schema
• SYS Schema
– A set of VIEWs on the Performance Schema
– A set of SPs to make things easier • to clean up performance schema tables
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Summary
• Using Performance Schema
– Data Collection
– As a tools
– Overhead! Enable what you want to see.
• Using SYS Schema
– Friendly VIEWs to explore performance data set
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