Thursday 8 March 2012

Another MySQL Tuning Tool

MySQL Configuration and Tuning

One thing I really don't like about MySQL compared to MS SQL is the number of configurable options and the lack of data management  views to help you diagnose performance issues. Yes there are tools available but I haven not come across anything as good as the Activity Monitor for an overview of your servers performance in MySQL.

Being able to quickly see the primary cause of performance issues in graph form, high CPU, memory, I/O, blocking, the processes causing the blocking and those effected by the blocks, performance intensive queries and so on in a visual format is very useful.

Another great thing about MS SQL is the amount of Data Management Views and the reports you can create to find the most expensive queries, those with missing indexes, those that require tuning or index rebuilding, query plan re-use or under-user etc are all very useful tools.

Therefore when I come across anything that is semi useful for performance tuning MySQL I will make a note of it and list it on this blog so that other Microsoft developers using LAMP, WAMP etc can benefit from them as well.

One tool I came across tonight which has gone into my rackspace server alongside other MySQL configuration analysers is the MySQL Performance Tuning Primer Script which along with others of a similar ilk will analyse your database settings from a SHOW /*!50000 GLOBAL */ STATUS command and then make recommendations that you can use in your MySQL.cnf file.

To install this script you will need to do the following.

  1. Open a SSH console window up.
  2. Move to the right folder e.g cd /usr/local/src/
  3. Use WGet to load the file to your server e.g wget
  4. Grant execute permission to the script e.g chmod u+x
  5. Try running the script e.g ./

You might get an error like I did on the first attempt which said:

Error: Command line calculator 'bc' not found!

If you don't know bc is (which I didn't) it is the command line arbitrary precision calculator from GNU and it is obviously used within the shell script we are trying to run.

Therefore you will need to install this as well by using apt-get. So run this:

apt-get install bc

Which will install the bc app.

Now try again e.g

/usr/local/src# ./

And you should get something like this:

Using login values from ~/.my.cnf
Testing for stored webmin passwords:
Could not auto detect login info!
Found potential sockets: /var/run/mysqld/mysqld.sock
Using: /var/run/mysqld/mysqld.sock
Would you like to provide a different socket?: [y/N] n
Do you have your login handy ? [y/N] : y
User: [enter your username e.g root or the password for the DB in question]
Password: [enter your password]

You will then get a report like the following and the option to create a new MySQL configuration file if you require it.

Would you like me to create a ~/.my.cnf file for you? [y/N] : n

- By: Matthew Montgomery -

MySQL Version 5.0.51a-24+lenny5-log x86_64

Uptime = 7 days 23 hrs 32 min 26 sec
Avg. qps = 10
Total Questions = 7286512
Threads Connected = 1

Server has been running for over 48hrs.
It should be safe to follow these recommendations

To find out more information on how each of these
runtime variables effects performance visit:
for info about MySQL's Enterprise Monitoring and Advisory Service

The slow query log is enabled.
Current long_query_time = 2 sec.
You have 178496 out of 7286569 that take longer than 2 sec. to complete
Your long_query_time seems to be fine

The binary update log is NOT enabled.
You will not be able to do point in time recovery

Current thread_cache_size = 8
Current threads_cached = 7
Current threads_per_sec = 0
Historic threads_per_sec = 0
Your thread_cache_size is fine

Current max_connections = 100
Current threads_connected = 1
Historic max_used_connections = 15
The number of used connections is 15% of the configured maximum.
Your max_connections variable seems to be fine.

No InnoDB Support Enabled!

Max Memory Ever Allocated : 153 M
Configured Max Per-thread Buffers : 262 M
Configured Max Global Buffers : 114 M
Configured Max Memory Limit : 376 M
Physical Memory : 1.01 G
Max memory limit seem to be within acceptable norms

Current MyISAM index space = 221 M
Current key_buffer_size = 64 M
Key cache miss rate is 1 : 3110
Key buffer free ratio = 14 %
You could increase key_buffer_size
It is safe to raise this up to 1/4 of total system memory;
assuming this is a dedicated database server.

Query cache is enabled
Current query_cache_size = 40 M
Current query_cache_used = 20 M
Current query_cache_limit = 2 M
Current Query cache Memory fill ratio = 50.83 %
Current query_cache_min_res_unit = 4 K
MySQL won't cache query results that are larger than query_cache_limit in size

Current sort_buffer_size = 2 M
Current read_rnd_buffer_size = 256 K
Sort buffer seems to be fine

Current join_buffer_size = 132.00 K
You have had 89958 queries where a join could not use an index properly
You should enable "log-queries-not-using-indexes"
Then look for non indexed joins in the slow query log.
If you are unable to optimize your queries you may want to increase your join_buffer_size to accommodate larger joins in one pass.

Note! This script will still suggest raising the join_buffer_size when
ANY joins not using indexes are found.

Current open_files_limit = 1024 files
The open_files_limit should typically be set to at least 2x-3x
that of table_cache if you have heavy MyISAM usage.
Your open_files_limit value seems to be fine

Current table_cache value = 200 tables
You have a total of 146 tables
You have 200 open tables.
Current table_cache hit rate is 6%, while 100% of your table cache is in use
You should probably increase your table_cache

Current max_heap_table_size = 200 M
Current tmp_table_size = 200 M
Of 985542 temp tables, 44% were created on disk
Perhaps you should increase your tmp_table_size and/or max_heap_table_size
to reduce the number of disk-based temporary tables
Note! BLOB and TEXT columns are not allow in memory tables.
If you are using these columns raising these values might not impact your ratio of on disk temp tables.

Current read_buffer_size = 128 K
Current table scan ratio = 998 : 1
read_buffer_size seems to be fine

Current Lock Wait ratio = 1 : 1205
You may benefit from selective use of InnoDB.
If you have long running SELECT's against MyISAM tables and perform frequent updates consider setting 'low_priority_updates=1'
If you have a high concurrency of inserts on Dynamic row-length tables consider setting 'concurrent_insert=2'.

Then you can take the recommendations and change the MySQL configuration file yourself in /etc/mysql/my.cnf before restarting the MySQL server so that the changes take effect e.g.

/usr/local/src# /etc/init.d/mysql restart
Stopping MySQL database server: mysqld.
Starting MySQL database server: mysqld.
Checking for corrupt, not cleanly closed and upgrade needing tables..

Just another MySQL report in the same ilk as and mysqlreport but still not as good as anything I have seen on MS SQL 2005-2008.

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