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Another MySQL PerformanceMorgan Tocker

mailto:morgan@mysql.commailto:morgan@mysql.com

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Topics Ill cover

How *not* to benchmark

Disk CPU RAM or Network? MySQL Topologies

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How *not* to benchmark

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My favorite quote...

I tested both MyISAM and InnoDB and accessing the sam1000 times it was always faster in MyISAM....

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Why?

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Why?

By using the same URL you almost guaranteed that it win:

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Why?

By using the same URL you almost guaranteed that it win:

The query_cache (if enabled)

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Why?

By using the same URL you almost guaranteed that it win:

The query_cache (if enabled)

The MySQL key_cache (if MyISAM) for the index blocks

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Why?

By using the same URL you almost guaranteed that it win:

The query_cache (if enabled)

The MySQL key_cache (if MyISAM) for the index blocks

The InnoDB buffer pool (both indexes and data) and the Iadaptive hash

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Why?

By using the same URL you almost guaranteed that it win:

The query_cache (if enabled)

The MySQL key_cache (if MyISAM) for the index blocks

The InnoDB buffer pool (both indexes and data) and the Iadaptive hash

A filesystem cache. Maybe even a disk cache, or the drive might be at the right location to minimize seek.

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What else is wrong?

Youve also omitted other key problems from your test.

Cant catch potential deadlocks, Table locking

Any issues where disk Starvation etc occurs.

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My second favorite quote.

My systems average load is 0.10 with 100 connections, so able to support somewhere up to 1000 connections.

Rarely true.

Bottlenecks shift.

Multi-cores and multi CPUs are exposing new problems.BUG #15815, BUG #30738, BUG #26442

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Tools to use

Apache benchmark (ab)

http_load

Similar to ab, can accept an input file of URLs (apache accemakes a good victim)

Custom shell scripts

curl $url

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Disk RAM CPU or Networ

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Potential Bottlenecks

DISK RAM

CPU Network

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Potential Bottlenecks

DISKThe number one bottleneck.

Seriously.RAM

CPU Network

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Potential Bottlenecks

DISKThe number one bottleneck.

Seriously.

RAMUse it to cheat - get o

your DISK whereve

CPU Network

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Potential Bottlenecks

DISKThe number one bottleneck.

Seriously.

RAMUse it to cheat - get o

your DISK whereve

CPUMay report as high if

heavy wait I/O.Network

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Potential Bottlenecks

DISKThe number one bottleneck.

Seriously.

RAMUse it to cheat - get o

your DISK whereve

CPUMay report as high if

heavy wait I/O.

NetworkMaximum throughp

normally an issue, butadd latency

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My Advice:

Better value in fixing the bigger problems first.

Sometimes this means not buying expensive CPUs and GigaEthernet cards.

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Warning! Your bottleneckmay change

Whats percentage of your data fits nicely into RAM?

Almost any sloppy design will work with a dataset of 1G

Can you afford the same when your dataset is 90G?

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My favorite unixy command

iostat -d 60 5 > /tmp/iostat.txt &

df -h

vmstat 60 5 > /tmp/vmstat.txt &

free

lsof

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My favorite unixy command(cont.)

ps aux

uptime

top

netstat

ping -f

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My advice: Hard Drives

RAID 10 is the best (slightly better write speed than RAID5

Be careful that cheaper cards apparently do RAID5 in some reduced performance way

Drive speed also counts (10K, 15K RPM)

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My advice: Hard Drives (con

Slower drives cant fsync() fast enough, so youll still be writ

Battery backed write caches on RAID controllers kick ars

You can distribute InnoDB log files or binary log files for beIO distribution

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Some things to try...

mount drives with noatime

experiment with different IO schedulers

Temporary tables that need to be created on disk in MySQLredirected to a tmpfs

Youll want to reduce the size of max_heap_table_size andtmp_table_size

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Topologies that scale

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In the beginning...

www

+ mysql

Internet

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The next logical step...

www

Internet

mysql

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The next logical step (cont

www

Internet

mysql

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Continued Growth...

www

Internet

master

reads

x N

slaves

writes

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Where this hits the wall..

Writes

Reads

Writes

Reads

Writes

Reads

Writes

Reads

Writes

Unused

Writes

Reads

Write

Read

* Single replication thread makes this even worse than it loo

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You need to (partition) shar

Use groups of Master, Slave, Slave for different tasks:

Do logging tables ever join on the other tables?

Maybe have a global user table and store user_details on dgroups of servers.

Different servers for searching

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The End(Heres where I givetime for other Q&A)