Sunday, 30 September 2007 20:48

Digging into mySQL settings can be time consuming, like with any other component. Most of the time, and just by changing a few settings, you can expect a performance increase. The problem is to change what, and to which value. This is where tuning-primer.sh help you:

Get this script, http://forge.mysql.com/projects/view.php?id=44 upload it, unzip it, and install it in your /etc folder. Then run it from the command line by entering ./path-to-file/tuning-primer.sh

MySQL Server must run a few days or weeks, or it wont be be safe to follow these recommendations.

To find out more information on how each of these runtime variables effects performance visit:
http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html

Here is an example of tuning-primer.sh output

SLOW QUERIES
Current long_query_time = 5 sec.
You have 2856 out of 4725688 that take longer than 5 sec. to complete
The slow query log is enabled.
Your long_query_time seems to be fine

WORKER THREADS
Current thread_cache_size = 128
Current threads_cached = 55
Current threads_per_sec = 0
Historic threads_per_sec = 0
Your thread_cache_size is fine

MAX CONNECTIONS
Current max_connections = 100
Current threads_connected = 15
Historic max_used_connections = 55
The number of used connections is 55% of the configured maximum.
Your max_connections variable seems to be fine.

MEMORY USAGE
Max Memory Ever Allocated : 305 M
Configured Max Per-thread Buffers : 1017 M
Configured Max Global Buffers : 143 M
Configured Max Memory Limit : 1 G
Total System Memory : 2.99 G
Max memory limit seem to be within acceptable norms

KEY BUFFER
Current MyISAM index space = 4 M
Current key_buffer_size = 5 M
Key cache miss rate is 1 : 3740
Key buffer fill ratio = 35.00 %
Your key_buffer_size seems to be too high.
Perhaps you can use these resources elsewhere

QUERY CACHE
Query cache is enabled
Current query_cache_size = 128 M
Current query_cache_used = 27 M
Current query_cach_limit = 2 M
Current Query cache fill ratio = 21.13 %
Your query_cache_size seems to be too high.
Perhaps you can use these resources elsewhere
MySQL won't cache query results that are larger than query_cache_limit in size

SORT OPERATIONS
Current sort_buffer_size = 4 M
Current record/read_rnd_buffer_size = 1020 K
Sort buffer seems to be fine

JOINS
Current join_buffer_size = 1.00 M
You have had 7065 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.