When I ran the first performance tests on our website using siege and its associated tool bombardment the I found that a page server from midgard was much slower than the equivalent page served as a plain html files and the greater the load the slower it got until when I got to about 40-50 concurrent users I got socket connection errors. Looking at top I could see that the system resources were being consumed by MySQL.

Use the command

$mysqld --help

to see what the default settings are for your mysql server. A lot of these parameters are not actually listed in your my.cnf file but are set when mysql is compiled. To override the defaults you have to add entries to your my.cnf file.

My output was this

back_log current value: 50
bdb_cache_size current value: 8388600
bdb_log_buffer_size current value: 0
bdb_max_lock current value: 10000
bdb_lock_max current value: 10000
binlog_cache_size current value: 32768
connect_timeout current value: 5
delayed_insert_timeout current value: 300
delayed_insert_limit current value: 100
delayed_queue_size current value: 1000
flush_time current value: 0
innodb_mirrored_log_groups current value: 1
innodb_log_files_in_group current value: 2
innodb_log_file_size current value: 5242880
innodb_log_buffer_size current value: 1048576
innodb_buffer_pool_size current value: 8388608
innodb_additional_mem_pool_size current value: 1048576
innodb_file_io_threads current value: 4
innodb_lock_wait_timeout current value: 50
innodb_thread_concurrency current value: 8
innodb_force_recovery current value: 0
interactive_timeout current value: 28800
join_buffer_size current value: 131072
key_buffer_size current value: 16773120
long_query_time current value: 10
lower_case_table_names current value: 0
max_allowed_packet current value: 1047552
max_binlog_cache_size current value: 4294967295
max_binlog_size current value: 1073741824
max_connections current value: 100
max_connect_errors current value: 10
max_delayed_threads current value: 20
max_heap_table_size current value: 16777216
max_join_size current value: 4294967295
max_sort_length current value: 1024
max_tmp_tables current value: 32
max_user_connections current value: 0
max_write_lock_count current value: 4294967295
myisam_max_extra_sort_file_size current value: 256
myisam_max_sort_file_size current value: 2047
myisam_sort_buffer_size current value: 8388608
net_buffer_length current value: 7168
net_retry_count current value: 10
net_read_timeout current value: 30
net_write_timeout current value: 60
open_files_limit current value: 0
query_buffer_size current value: 0
record_buffer current value: 131072
record_rnd_buffer current value: 0
slave_net_timeout current value: 3600
slow_launch_time current value: 2
sort_buffer current value: 524280
table_cache current value: 64
thread_concurrency current value: 10
thread_cache_size current value: 0
tmp_table_size current value: 33554432
thread_stack current value: 65536
wait_timeout current value: 28800

Now looking at this I saw a number of things that I would like to tweak.