MySQL configuration - The most important Variables

MySQL Konfiguration - die wichtigsten
Parameter

DOAG SIG MySQL – Performance
13. März 2012, Wiesbaden

Oli Sennhauser
Senior MySQL Consultant, FromDual GmbH

oli.sennhauser@fromdual.com

www.fromdual.com 1

FromDual GmbH
● FromDual bietet neutral und unabhängig:
● Beratung für MySQL
● Support für MySQL und Galera Cluster
● Remote-DBA / MySQL Betrieb
● Schulung für MySQL
● Oracle Silber Partner (OPN)

www.fromdual.com

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Kunden

www.fromdual.com 3

Inhalt

MySQL Konfiguration
➢
FromDual Perfromance Waage
➢
The Big 9!
➢
InnoDB
➢
MyISAM
➢
MySQL
➢
Weitere Parameter

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MySQL Tuning
● Welche Storage Engine verwendet Ihr zur
Zeit?
● Welchen MySQL Release? (→ 5.1 und neuer)
● Zur Zeit: ca. 330 MySQL Parameter
→ aber nur ca. 8 (9) davon sind signifikant!
→ Grob-Tuning
● Alle anderen nur nach ausführlichem
Benchmarken
→ Fine-Tuning
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MySQL Architektur
Applikation / Client

Thread Connection mysqld
Cache Manager Parser
Optimizer
User Au-
thentication
Access Control
Command Table Open
Logging
Dispatcher Cache (.frm, fh)
Table Manager
Query Query Cache Table Definition
Cache Module Cache (tbl def.)

Handler Interface

MyISAM InnoDB Memory NDB PBMS Aria XtraDB Federated-X ...

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Bevor wir anfangen!
● Kunde fragt mich: Kann mein System 30% mehr
Last vertragen?
● Chemische Verfahrenstechnik:

● Gibt es Unterschiede zu eine DB basierten
System?
● Was brauche ich um diese Frage zu beantworten?

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Messen, messen, messen...
● Messen!
● Idealfall: Nur ein Parameter aufs mal
ändern!

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The big 9!
● InnoDB: 5
● InnoDB Buffer Pool: 2
● InnoDB Log File: 3
● MyISAM: 1
● Key Buffer: 1
● MySQL: 3
● Query Cache: 1
● Table_*_cache: 2

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InnoDB Buffer Pool
● InnoDB cached: Daten UND Indizes
● Grösse: innodb_buffer_pool_size
● in Byte (M, G)
● Pages à 16k (5.6: 4k, 8k, 16k)
● Repräsentation der Platte im FS Cache

Speicher:
● Ca. 80% vom RAM auf dedizier-
ter InnoDB Maschine

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InnoDB Buffer Pool Informationen
● Messen:
SHOW GLOBAL STATUS LIKE 'innodb_buffer_pool_pages%';

+++
| Variable_name                    | Value    |
+++
| Innodb_buffer_pool_pages_data    | 9175     |
| Innodb_buffer_pool_pages_misc    | 40       | +
| Innodb_buffer_pool_pages_free    | 1024     | +
| Innodb_buffer_pool_pages_total   | 10239    | =

| Innodb_buffer_pool_pages_dirty   | 289      | 3.1%
| Innodb_buffer_pool_pages_data    | 9175     |
+++

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InnoDB Buffer Pool von InnoDB
Status
SHOW ENGINE INNODB STATUSG

BUFFER POOL AND MEMORY

Total memory allocated 171704320
Dictionary memory allocated 2473598
Buffer pool size   10239
Free buffers       1024
Database pages     9185
Old database pages 3370
Modified db pages  812
Pending reads 0
Pending writes: LRU 0, flush list 0 single page 0
Pages made young 1768431, not young 0
1.00 youngs/s, 0.00 nonyoungs/s
Pages read 1197328, created 215334, written 22307309
1.00 reads/s, 1.00 creates/s, 0.00 writes/s
Buffer pool hit rate 1000 / 1000, youngmaking rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s,
Random read ahead 0.00/s
LRU len: 9185, unzip_LRU len: 0
I/O sum[3125]:cur[2], unzip sum[0]:cur[0]

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InnoDB Buffer Pool Monitoring
● Es ist wünschenswert, aber meist
illusorisch, alle Daten im RAM zu halten!

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InnoDB Buffer Pool Monitoring
● Einfluss von Partitionierung auf den InnoDB
Buffer Pool:

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InnoDB Buffer Pool Instanzen
● InnoDB Buffer Pool Instanzen!
● Neu mit MySQL 5.5
● Bei sehr viel RAM
● Bei hoher Concurrency
→ Locks auf Buffer Pool Verwaltungsstruktur
→ Eigene Free List, Flust List, LRU List, Buffer Pool
Mutex, etc.
● Hash-Verteilung (random?)
● innodb_buffer_pool_instances
● Sinnvoll ab 2 Gb
● min. 1 Gb pro Instanz
● max. #cores
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InnoDB Log File
● innodb_flush_log_at_trx_commit
● 0, 2 für Performance, 1 für Sicherheit
– 0: 1/s + fsync
– 1: COMMIT + fsync FS Cache

– 2: COMMIT + 1/s fsync
● innodb_log_file_size
● Grösser = schneller, aber längere
Recovery Zeiten → 2 x 256 M
● sync_binlog
● != 0 → langsam(er)
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InnoDB Log File Information
SHOW ENGINE INNODB STATUSG

LOG

Log sequence number 404010398185
Log flushed up to   404010198753 = 199432 byte log buffer

Log flushed up to   404010198753
Last checkpoint at  404010110312 =  88441 byte log file

0 pending log writes, 0 pending chkp writes
152844 log i/o's done, 0.50 log i/o's/second

SHOW GLOBAL STATUS LIKE 'innodb_os_log_%';
+++
+++
| Innodb_os_log_fsyncs         | 153643      |
| Innodb_os_log_pending_fsyncs | 0           |
| Innodb_os_log_pending_writes | 0           |
+++

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InnoDB Log File Monitoring

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MyISAM Key Buffer
● MyISAM cached nur Indizes!
→ Key Buffer
→ Daten: File System Cache
● key_buffer_size
● ca. 25 – 33% vom RAM auf dedizierter Maschine
● ca. 67 – 75% vom RAM für File System Cache
● Üblicherweise 1k pages

www.fromdual.com 21

MyISAM Key Buffer Information
● Key Buffer Hit Ratio:
read_requests / (read_requests + reads) x 100
● Key_blocks_used: High Water Mark!
SHOW GLOBAL STATUS LIKE 'key%';
+++
+++
| Key_blocks_not_flushed | 0      |
| Key_blocks_unused      | 1674   |
| Key_blocks_used        | 9      |
| Key_read_requests      | 130434 |
| Key_reads              | 0      |
+++

shell> free
             total       used       free     shared    buffers     cached
Mem:      16431960    6190408   10241552          0     408832    1719944

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MyISAM Monitoring
● Key Buffer mehr als genügend gross!

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Query Cache
● Cached SELECT Queries
● Hash, Tabellen, Resultat
● Performance Booster bei:
● Lesen >> Schreiben
● Geringer Concurrency
● query_cache_size / query_cache_type
● Nicht zu gross machen (<= 128 M)
● Bei sehr hoher Concurrency schädlich!
● Global Query Cache Mutex
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Query Cache Informationen
● Schlechtes Hits / Inserts Verhältnis:
● Ist: 0.26, Soll: >= 1.2
● Insert: 10 – 20 % Overhead
● Query Cache Hit Ratio: 16.9%
● Qcache_hits / (Com_select + Qcache_hits) x 100
SHOW GLOBAL STATUS LIKE 'qcache%';
+++
+++
| Com_select              | 5049720 |
| Qcache_free_memory      | 1995376 |
| Qcache_hits             | 1026597 |
| Qcache_inserts          | 3911380 |
| Qcache_lowmem_prunes    | 2529208 |
| Qcache_not_cached       | 1138305 |
| Qcache_queries_in_cache | 1357    |
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+++

Query Cache Monitoring
● Um xx:25 macht „jemand“ den Query Cache
„kaputt“:

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MySQL Parameter
● table_open_cache
● Cached File Handles
● Laufende Connections x be-
nutze Tabellen
→ 2 – 4k ist nicht ungewöhn-
lich!
● Wenn zu klein → massive Performance-Probleme!
● Hat Einfluss auf open-files-limit!
● table_definition_cache
● Cached .frm File (Tabellenstruktur)
● 512 – 4096 ist nicht ungewöhnlich!
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MySQL Parameter Informationen
SHOW GLOBAL STATUS LIKE 'open%table%s';
+++
+++
| Open_table_definitions   | 100   |
| Open_tables              | 102   |
| Opened_table_definitions | 100   |
| Opened_tables            | 109   |
+++

SHOW GLOBAL STATUS LIKE 'open%table%s';
+++
+++
| Open_table_definitions   | 67321    |
| Open_tables              | 131023   |
| Opened_table_definitions | 6177337  |
| Opened_tables            | 12489056 |
+++

SHOW OPEN TABLES;
+++++
| Database           | Table                     | In_use | Name_locked |
+++++
| crm                | saved_search              |      0 |           0 |
| zabbix             | users                     |      0 |           0 |
...

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MySQL Parameter Monitoring

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Weitere InnoDB Parameter
● Viele Neuerungen mit MySQL 5.5 und 5.6!
● InnoDB Log File / Buffer:
● innodb_log_group_home_dir = ./
● Default datadir
● Trennen von sequentiellem I/O und random I/O
● innodb_log_buffer_size = 8M
● Für grosse Transaktionen
● Innodb_log_waits > 0

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● innodb_file_per_table = 1
● 1 grosses Sytem TS File vs.
● 1 kleines System TS File + 1 File pro Tabelle
● Vorteil: Diskplatz wird wieder freigegeben
● innodb_data_home_dir
● Default datadir
● Splitten von random I/O auf Daten und sequential I/O auf Log Files
● innodb_data_file_path = ibdata1:10M:autoextend
● innodb_autoextend_increment = 8
● Achtung: 8 Mbyte!!!
● Gilt nur für System TS File
● innodb_file_format = Antelope
● Default (= alt)
● Barracuda ermöglicht File compression
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● innodb_flush_method = data files log files
● Ausprobieren! open flush open flush
default normal fsync normal fsync
●
O_DSYNC O_SYNC fsync O_SYNC O_SYNC
O_DIRECT O_DIRECT fsync normal fsync
● innodb_io_capacity = 200
● Raid-1/10 #Disks / 2 x 200
● innodb_read_io_threads = 4
● innodb_write_io_threads = 4
● Pending reads > innodb_read_io_threads x 64
● Pending writes
● innodb_use_native_aio = 1
● Linux und Windows
● Pending reads / writes
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Weitere MySQL Parameter
● thread_cache_size    =    8
● tmp_table_size       =   16M
● max_heap_table_size  =   16M
● max_connections      =  151
● max_user_connections =    0
● open_files_limit     = 1024

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● join_buffer_size       = 128k >  8M
● read_buffer_size       = 128k >  2M
● read_rnd_buffer_size   = 256k > 16M
● sort_buffer_size       = 256k >  8M

● binlog_format          = ROW
● binlog_cache_size      = 32k > 1M
● binlog_stmt_cache_size = 32k > 1M
● binlog_row_image       = FULL
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● datadir                    = /var/lib/mysql/
● default_storage_engine     = InnoDB
● default_tmp_storage_engine = InnoDB

● innodb_old_blocks_pct      = 37
● innodb_old_blocks_time     = 0  > 500?

● key_cache_age_threshold    = 300
● key_cache_division_limit   = 100 > 63?

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● long_query_time          = 10.000000 > 0.5?
● slow_query_log           = OFF > 1
● slow_query_log_file      = /var/lib/mysql/slow.log

● optimizer_switch         = index_merge=on,
index_merge_union=on,index_merge_sort_union=on
● optimizer_trace          = enabled=off,end_marker=off,
one_line=off
● optimizer_trace_features = greedy_search=on,
range_optimizer=on,dynamic_range=on,repeated

● performance_schema       = ON

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Weitere Hilfe
● Wie messen?
● SHOW GLOBAL STATUS;
● SHOW ENGINE INNODB STATUSG
● ca. 330 Variablen
● ca. 310 Status Informationen
● MySQL Database Health Check:
● http://www.fromdual.com/mysql-database-health-check
● MySQL Doku, Server Status Variablen:
http://dev.mysql.com/doc/refman/5.5/en/server-status-variables.html
● MySQL Performance Monitor:
● http://www.fromdual.ch/mysql-performance-monitor
● Auch als Monitoring as a Service (MaaS) Angebot!
www.fromdual.com 37

Q&A

Fragen ?

Diskussion?

Wir haben noch Zeit für persönliche und
indviduelle Beratung

und bieten

Support, Schulung und Betrieb für MySQL

www.fromdual.com 38

MySQL configuration - The most important Variables

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