xtradb opensource storage engine for mysql

XtraDB OpenSource Storage Engine for MySQL

OSCON 2009

Vadim Tkachenko,

Ryan Lowe

Percona Inc

MySQLPerformanceBlog.com

Who are we ?

• http://MysqlPerformanceBlog.com• Vadim Tkachenko

– Co-Founder of Percona Inc• Lead of R&D department

– Co-Author “High Performance MySQL” 2nd edition book

• Ryan Lowe– Senior Consultant, Percona Inc

• Coordinator, USA Consulting Group

• Special Thanks Yasufumi Kinoshita– Not here, but author of most work

XTraDB OpenSource Storage Engine for MySQL

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What is this talk about?

• XtraDB storage engine for MySQL – Enhanced version of InnoDB

• Two main focuses– Performance improvements– “Usability” improvements

• Make InnoDB a bit more friendly • World changed since time of Pentium 100MHz and 8MB of RAM

– But many such assumptions still in InnoDB code


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MySQL Architecture in short


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XtraDB – drop in replacement for InnoDB

Why we do it

• Gather all patches we have into single engine• Most requirements and changes come from

practical work with customers• We need InnoDB fully utilizing modern hardware

today– 16 cores– RAIDs– SSD / FusionIO / other storage technologies– InnoDB is not able to do that today, developed ~10 year

ago


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History

• Started with patches for MySQL 5.0– Still support

• https://launchpad.net/percona-patches• Percona builds for MySQL 5.0• http://www.percona.com/mysql/


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XtraDB, what is it

• Enhanced InnoDB• Better hardware utilization• Better usability• Open for third-party patches• http://www.percona.com/docs/wiki/percona-

xtradb:start• https://launchpad.net/percona-xtradb• Found in twitter: “We moved a database-set of 40 servers to mysql-5.1.34 +

xtradb and are running our former workload with 6 servers. ramonvanalteren“


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XtraDB base

• MySQL 5.1– “easy” to remove and plug new engine

• InnoDB plugin– New features– Focus of development of InnoDB team– Designed to plug into 5.1


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Performance Improvements


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Scalability

• Split buffer_pool mutex – Replace global lock on innodb_buffer_pool on several

small parts– Decrease contention on single lock on multi-cores systems

• Extra rollback segments– InnoDB uses just 1, again contention on multi-concurrency

load

• Extra undo slots– By default max 1024 concurrent transactions, we increase

to 4076


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IO improvements

• InnoDB IO– Set of patches to improve InnoDB IO performance – Several parts – some of them now in MySQL 5.4


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IO – multiple threads

• Read_io_threads– Number of threads for reads requests (by default 1)– Not really useful as used only for read-ahead requests

• Write_io_threads– Number of threads for write requests (by default 1)– This is one you may want to use on system with multiple

disks

• IO_capacity– Amount of IO operations per second InnoDB assumes

server can do (by default 100, which is not right assumptions for modern systems)


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IO – Adaptive checkpoint

• InnoDB flushing of dirty buffer_pool pages may be intensive

• Lack of free pages may be controlled by innodb_max_dirty_pages_pct

• Flushing at the moment of checkpoint is not controllable, intensive and may hurt


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Adaptive checkpointing


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InnoDB default behavior, hiccups during buffer_pool flushing

Adaptive checkpoint

• What we do:• Flush pages more intensive

– the closer checkpoint the more intensive


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Adaptive_checkpoint

• Adaptive_checkpoint=1


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IO Control of Insert buffer

• Ibuf_max_size – maximal size of insert buffer (by default can be half of buffer_pool)

• Ibuf_accel_rate – IO rate for background thread, works in pair with io_capacity


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IO – multiple pages

• Read_ahead = (both | linear | random)– Control to use or not internal InnoDB read-ahead logic


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IO – multiple pages

• Flush_neighbor_pages = (yes|no)– By default InnoDB also writes neighborhoods of flushing

pages

• All these operations were made for disks with expensive (in time sense) random reads – may be not needed for SSD / FusionIO / other devices with cheap random reads


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Extra rollback segments

• By default InnoDB uses single segment protected by mutex

• Sensitive in intensive parallel insert load


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Fix group commit

• “Broken” in 5.0– Problem appears on slow disks with enabled binary-logs


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Benchmark

• Tpcc-like workload• 100 Warehouses (about 10GB of data)• Buffer_pool=16GB (in memory) | 3GB (io-bound)• System: Dell PowerEdge R900, RAID 10 on 8

disks, RAM 32GB– O_DIRECT for InnoDB, ext filesystem

• 5.1-XtraDB vs 5.1-standard


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Benchmark


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Usability patches


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Limit data dictionary

• Problem:– Data dictionary entry of once opened table kept in

memory forever (or while DELETE table)– Is not problem for regular usage (100-1000 tables)– Is problem for instances with 10K+ tables

• 10GB+ of memory just allocated for data dictionary entries

• Our solution:– LRU based data dictionary entries– Remove from memory oldest entries if limit reached


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Show buffer pool content

• What is in buffer_pool


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select space,offset, RECORDS, DATASIZE, INDEX_NAME,TABLE_SCHEMA,TABLE_NAME from information_schema.INNODB_BUFFER_POOL_CONTENT limit 10;+-------+---------+---------+----------+------------+--------------+-------------+| space | offset | RECORDS | DATASIZE | INDEX_NAME | TABLE_SCHEMA | TABLE_NAME |+-------+---------+---------+----------+------------+--------------+-------------+| 1584 | 640643 | 9 | 10312 | PRIMARY | art104 | article104 | | 1648 | 2100 | 135 | 15226 | PRIMARY | art114 | author114 | | 1492 | 4507 | 158 | 15130 | PRIMARY | art87 | author87 | | 1406 | 17498 | 141 | 16056 | img_status | art52 | img_out52 | | 1466 | 47632 | 49 | 15140 | PRIMARY | art62 | img_out62 | | 1470 | 1395457 | 24 | 14769 | PRIMARY | art84 | article84 | | 1460 | 16025 | 62 | 15174 | PRIMARY | art61 | img_out61 | | 1458 | 560956 | 20 | 14977 | PRIMARY | art61 | article61 | | 1466 | 67953 | 56 | 15182 | PRIMARY | art62 | img_out62 | | 1621 | 162962 | 46 | 15134 | PRIMARY | art110 | link_out110 | +-------+---------+---------+----------+------------+--------------+-------------+

Show memory usage

• Extended information about memory consuming


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---------------------- BUFFER POOL AND MEMORY ---------------------- Total memory allocated 328830416; in additional pool allocated 2117120 + Internal hash tables (constant factor + variable factor) + Adaptive hash index 4839388 (4425628 + 413760) + Page hash 138716 + Dictionary cache 3383508 (3320220 + 63288) + File system 41848 (41336 + 512) + Lock system 332788 (332468 + 320) + Recovery system 0 (0 + 0) + Threads 41900 (41348 + 552) Buffer pool size 16384 + Buffer pool size, bytes 268435456 Free buffers 12396

Show locks held• ---TRANSACTION 0 163390, ACTIVE 0 sec, process no 15571, OS thread id 1159485776 inserting • mysql tables in use 1, locked 1 • 7 lock struct(s), heap size 1216, undo log entries 4 • MySQL thread id 15, query id 15455 127.0.0.1 root update • INSERT INTO history(h_c_d_id, h_c_w_id, h_c_id, h_d_id, h_w_id, h_date, h_amount, h_data) VALUES(?, ?, ?, ?, ?, ?, • ?, ?) • Trx read view will not see trx with id >= 0 163391, sees < 0 163086 • TABLE LOCK table `test/warehouse` trx id 0 163390 lock mode IX • RECORD LOCKS space id 10 page no 3 n bits 168 index `PRIMARY` of table `test/warehouse` trx id 0 163390 lock_mode X• locks rec but not gap • TABLE LOCK table `test/district` trx id 0 163390 lock mode IX

• RECORD LOCKS space id 18 page no 7 n bits 216 index `PRIMARY` of table `test/district` trx id 0 163390 lock_mode X locks rec but not gap

• TABLE LOCK table `test/customer` trx id 0 163390 lock mode IX • RECORD LOCKS space id 19 page no 57918 n bits 96 index `PRIMARY` of table `test/customer` trx id 0 163390 lock_mode

X locks rec but not gap • TABLE LOCK table `test/history` trx id 0 163390 lock mode IX


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TransactionalReplication

• Similar to Google’s patch• Information in relay-log.info is not consistent with

InnoDB state.– When server crash MySQL will repeat several transaction

• You are lucky if replication fails on “Duplicate key error”• In worst case you will have several transactions executed twice

• Our solution: store information of binary log name and position and relay-log name and position in InnoDB transactional log file


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Move tables between servers


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• Before was available only for MyISAM– For InnoDB only full copy of database– Very painful if you have 100GB+ of data

• Useful for:– Restore only table (from backup or master)– Copy only single table to QA– Re-sharding data

Fast Recovery

• Start InnoDB after crash takes ages– The same from snapshot backup

• We changed internal InnoDB algorithm of handling list of pages


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And last but not least

• XtraBackup– OpenSource hot backup of XtraDB / InnoDB tables– Incremental / Differential backups– Stream backup (tar) directly to remote server / tape– https://launchpad.net/percona-xtrabackup– http://www.percona.com/docs/wiki/percona-

xtrabackup:start


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Plans

• Still hunt performance improvements• Operations tasks:

– Preload table / index into buffer_pool.– Several buffer_pools– Open InnoDB tables in parallel

• Currently serialized

– Different improvements on statistics– Full list of ideas

• http://www.percona.com/docs/wiki/devplan:start:ideas


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Questions ?

• Thank you for coming!


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xtradb opensource storage engine for mysql

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