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I have a Web server running on RHEL that is running Apache and MySQL. It has a Quad core 3.2Ghz Xeon CPU and 8 Gigs of RAM Most of the time, we don't have any issues at all.

Our web application is very database intensive. When our usage gets pretty heavy MySQL will peg out at using 24.9% of the cpu. Most of the time, it hangs around below 5%. I have speculated that it is only using one core of the CPU and it is pegging out that core but TOP shows me in the cpu column that mysqld changes cores even while the usage stays at 24.9%. When it does this MySQL gets painfully slow as it is queuing up queries Is there some magic configuration that will tell mysql to use more cpu when it needs to? Also, any other advice on my configuration would be helpful.

We run two applications on this server. One that runs Innodb but doesn't get much usage (it has been replaced by the other app), and one that runs MyIsam and gets lots of use. Overall, our whole mysql data directory is something like 13Gigs if that matters at all.

Here is my config:

[root@ProductionLinux root]# cat /etc/my.cnf
[mysqld]
server-id       = 71
log-bin         = /var/log/mysql/mysql-bin.log
binlog-do-db    = oldapplication
binlog-do-db    = newapplication
binlog-do-db    = support
thread_cache_size = 30
key_buffer_size = 256M
table_cache = 256
sort_buffer_size = 4M
read_buffer_size = 1M
skip-name-resolve

innodb_data_home_dir            = /usr/local/mysql/data/
innodb_data_file_path           = InnoDB:100M:autoextend
set-variable                    = innodb_buffer_pool_size=70M
set-variable                    = innodb_additional_mem_pool_size=10M
set-variable                    = max_connections=500
innodb_log_group_home_dir       = /usr/local/mysql/data
innodb_log_arch_dir             = /usr/local/mysql/data
set-variable                    = innodb_log_file_size=20M
set-variable                    = innodb_log_buffer_size=8M
innodb_flush_log_at_trx_commit  = 1
log-queries-not-using-indexes
log-error = /var/log/mysql/mysql-error.log
mysql> show variables;
+---------------------------------+-----------------------------------------------------------------------------+
| Variable_name                   | Value                                                                       |
+---------------------------------+-----------------------------------------------------------------------------+
| auto_increment_increment        | 1                                                                           |
| auto_increment_offset           | 1                                                                           |
| automatic_sp_privileges         | ON                                                                          |
| back_log                        | 50                                                                          |
| basedir                         | /usr/local/mysql-standard-5.0.18-linux-x86_64-glibc23/                      |
| binlog_cache_size               | 32768                                                                       |
| bulk_insert_buffer_size         | 8388608                                                                     |
| character_set_client            | latin1                                                                      |
| character_set_connection        | latin1                                                                      |
| character_set_database          | latin1                                                                      |
| character_set_results           | latin1                                                                      |
| character_set_server            | latin1                                                                      |
| character_set_system            | utf8                                                                        |
| character_sets_dir              | /usr/local/mysql-standard-5.0.18-linux-x86_64-glibc23/share/mysql/charsets/ |
| collation_connection            | latin1_swedish_ci                                                           |
| collation_database              | latin1_swedish_ci                                                           |
| collation_server                | latin1_swedish_ci                                                           |
| completion_type                 | 0                                                                           |
| concurrent_insert               | 1                                                                           |
| connect_timeout                 | 5                                                                           |
| datadir                         | /usr/local/mysql/data/                                                      |
| date_format                     | %Y-%m-%d                                                                    |
| datetime_format                 | %Y-%m-%d %H:%i:%s                                                           |
| default_week_format             | 0                                                                           |
| delay_key_write                 | ON                                                                          |
| delayed_insert_limit            | 100                                                                         |
| delayed_insert_timeout          | 300                                                                         |
| delayed_queue_size              | 1000                                                                        |
| div_precision_increment         | 4                                                                           |
| engine_condition_pushdown       | OFF                                                                         |
| expire_logs_days                | 0                                                                           |
| flush                           | OFF                                                                         |
| flush_time                      | 0                                                                           |                                                             |
| ft_max_word_len                 | 84                                                                          |
| ft_min_word_len                 | 4                                                                           |
| ft_query_expansion_limit        | 20                                                                          |
| ft_stopword_file                | (built-in)                                                                  |
| group_concat_max_len            | 1024                                                                        |
| have_archive                    | YES                                                                         |
| have_bdb                        | NO                                                                          |
| have_blackhole_engine           | NO                                                                          |
| have_compress                   | YES                                                                         |
| have_crypt                      | YES                                                                         |
| have_csv                        | NO                                                                          |
| have_example_engine             | NO                                                                          |
| have_federated_engine           | NO                                                                          |
| have_geometry                   | YES                                                                         |
| have_innodb                     | YES                                                                         |
| have_isam                       | NO                                                                          |
| have_ndbcluster                 | NO                                                                          |
| have_openssl                    | NO                                                                          |
| have_query_cache                | YES                                                                         |
| have_raid                       | NO                                                                          |
| have_rtree_keys                 | YES                                                                         |
| have_symlink                    | YES                                                                         |
| init_connect                    |                                                                             |
| init_file                       |                                                                             |
| init_slave                      |                                                                             |
| innodb_additional_mem_pool_size | 10485760                                                                    |
| innodb_autoextend_increment     | 8                                                                           |
| innodb_buffer_pool_awe_mem_mb   | 0                                                                           |
| innodb_buffer_pool_size         | 73400320                                                                    |
| innodb_checksums                | ON                                                                          |
| innodb_commit_concurrency       | 0                                                                           |
| innodb_concurrency_tickets      | 500                                                                         |
| innodb_data_file_path           | InnoDB:100M:autoextend                                                      |
| innodb_data_home_dir            | /usr/local/mysql/data/                                                      |
| innodb_doublewrite              | ON                                                                          |
| innodb_fast_shutdown            | 1                                                                           |
| innodb_file_io_threads          | 4                                                                           |
| innodb_file_per_table           | OFF                                                                         |
| innodb_flush_log_at_trx_commit  | 1                                                                           |
| innodb_flush_method             |                                                                             |
| innodb_force_recovery           | 0                                                                           |
| innodb_lock_wait_timeout        | 50                                                                          |
| innodb_locks_unsafe_for_binlog  | OFF                                                                         |
| innodb_log_arch_dir             | /usr/local/mysql/data                                                       |
| innodb_log_archive              | OFF                                                                         |
| innodb_log_buffer_size          | 8388608                                                                     |
| innodb_log_file_size            | 20971520                                                                    |
| innodb_log_files_in_group       | 2                                                                           |
| innodb_log_group_home_dir       | /usr/local/mysql/data                                                       |
| innodb_max_dirty_pages_pct      | 90                                                                          |
| innodb_max_purge_lag            | 0                                                                           |
| innodb_mirrored_log_groups      | 1                                                                           |
| innodb_open_files               | 300                                                                         |
| innodb_support_xa               | ON                                                                          |
| innodb_sync_spin_loops          | 20                                                                          |
| innodb_table_locks              | ON                                                                          |
| innodb_thread_concurrency       | 20                                                                          |
| innodb_thread_sleep_delay       | 10000                                                                       |
| interactive_timeout             | 28800                                                                       |
| join_buffer_size                | 131072                                                                      |
| key_buffer_size                 | 268435456                                                                   |
| key_cache_age_threshold         | 300                                                                         |
| key_cache_block_size            | 1024                                                                        |
| key_cache_division_limit        | 100                                                                         |
| language                        | /usr/local/mysql-standard-5.0.18-linux-x86_64-glibc23/share/mysql/english/  |
| large_files_support             | ON                                                                          |
| large_page_size                 | 0                                                                           |
| large_pages                     | OFF                                                                         |
| license                         | GPL                                                                         |
| local_infile                    | ON                                                                          |
| locked_in_memory                | OFF                                                                         |
| log                             | OFF                                                                         |
| log_bin                         | ON                                                                          |
| log_bin_trust_function_creators | OFF                                                                         |
| log_error                       | /var/log/mysql/mysql-error.log                                              |
| log_slave_updates               | OFF                                                                         |
| log_slow_queries                | OFF                                                                         |
| log_warnings                    | 1                                                                           |
| long_query_time                 | 10                                                                          |
| low_priority_updates            | OFF                                                                         |
| lower_case_file_system          | OFF                                                                         |
| lower_case_table_names          | 0                                                                           |
| max_allowed_packet              | 1048576                                                                     |
| max_binlog_cache_size           | 18446744073709551615                                                        |
| max_binlog_size                 | 1073741824                                                                  |
| max_connect_errors              | 10                                                                          |
| max_connections                 | 500                                                                         |
| max_delayed_threads             | 20                                                                          |
| max_error_count                 | 64                                                                          |
| max_heap_table_size             | 16777216                                                                    |
| max_insert_delayed_threads      | 20                                                                          |
| max_join_size                   | 18446744073709551615                                                        |
| max_length_for_sort_data        | 1024                                                                        |
| max_relay_log_size              | 0                                                                           |
| max_seeks_for_key               | 18446744073709551615                                                        |
| max_sort_length                 | 1024                                                                        |
| max_sp_recursion_depth          | 0                                                                           |
| max_tmp_tables                  | 32                                                                          |
| max_user_connections            | 0                                                                           |
| max_write_lock_count            | 18446744073709551615                                                        |
| multi_range_count               | 256                                                                         |
| myisam_data_pointer_size        | 6                                                                           |
| myisam_max_sort_file_size       | 9223372036854775807                                                         |
| myisam_recover_options          | OFF                                                                         |
| myisam_repair_threads           | 1                                                                           |
| myisam_sort_buffer_size         | 8388608                                                                     |
| myisam_stats_method             | nulls_unequal                                                               |
| net_buffer_length               | 16384                                                                       |
| net_read_timeout                | 30                                                                          |
| net_retry_count                 | 10                                                                          |
| net_write_timeout               | 60                                                                          |
| new                             | OFF                                                                         |
| old_passwords                   | OFF                                                                         |
| open_files_limit                | 2510                                                                        |
| optimizer_prune_level           | 1                                                                           |
| optimizer_search_depth          | 62                                                                          |
| pid_file                        | /usr/local/mysql/data/ProductionLinux.pid                                   |
| port                            | 3306                                                                        |
| preload_buffer_size             | 32768                                                                       |
| protocol_version                | 10                                                                          |
| query_alloc_block_size          | 8192                                                                        |
| query_cache_limit               | 1048576                                                                     |
| query_cache_min_res_unit        | 4096                                                                        |
| query_cache_size                | 0                                                                           |
| query_cache_type                | ON                                                                          |
| query_cache_wlock_invalidate    | OFF                                                                         |
| query_prealloc_size             | 8192                                                                        |
| range_alloc_block_size          | 2048                                                                        |
| read_buffer_size                | 1044480                                                                     |
| read_only                       | OFF                                                                         |
| read_rnd_buffer_size            | 262144                                                                      |
| relay_log_purge                 | ON                                                                          |
| relay_log_space_limit           | 0                                                                           |
| rpl_recovery_rank               | 0                                                                           |
| secure_auth                     | OFF                                                                         |
| server_id                       | 71                                                                          |
| skip_external_locking           | ON                                                                          |
| skip_networking                 | OFF                                                                         |
| skip_show_database              | OFF                                                                         |
| slave_compressed_protocol       | OFF                                                                         |
| slave_load_tmpdir               | /tmp/                                                                       |
| slave_net_timeout               | 3600                                                                        |
| slave_skip_errors               | OFF                                                                         |
| slave_transaction_retries       | 10                                                                          |
| slow_launch_time                | 2                                                                           |
| socket                          | /tmp/mysql.sock                                                             |
| sort_buffer_size                | 4194296                                                                     |
| sql_mode                        |                                                                             |
| sql_notes                       | ON                                                                          |
| sql_warnings                    | ON                                                                          |
| storage_engine                  | MyISAM                                                                      |
| sync_binlog                     | 0                                                                           |
| sync_frm                        | ON                                                                          |
| sync_replication                | 0                                                                           |
| sync_replication_slave_id       | 0                                                                           |
| sync_replication_timeout        | 10                                                                          |
| system_time_zone                | CST                                                                         |
| table_cache                     | 256                                                                         |
| table_lock_wait_timeout         | 50                                                                          |
| table_type                      | MyISAM                                                                      |
| thread_cache_size               | 30                                                                          |
| thread_stack                    | 262144                                                                      |
| time_format                     | %H:%i:%s                                                                    |
| time_zone                       | SYSTEM                                                                      |
| timed_mutexes                   | OFF                                                                         |
| tmp_table_size                  | 33554432                                                                    |
| tmpdir                          |                                                                             |
| transaction_alloc_block_size    | 8192                                                                        |
| transaction_prealloc_size       | 4096                                                                        |
| tx_isolation                    | REPEATABLE-READ                                                             |
| updatable_views_with_limit      | YES                                                                         |
| version                         | 5.0.18-standard-log                                                         |
| version_comment                 | MySQL Community Edition - Standard (GPL)                                    |
| version_compile_machine         | x86_64                                                                      |
| version_compile_os              | unknown-linux-gnu                                                           |
| wait_timeout                    | 28800                                                                       |
+---------------------------------+-----------------------------------------------------------------------------+
210 rows in set (0.00 sec)
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2 Answers

up vote 1 down vote accepted

Because you use a OLD version of MySQL that don't scale well with multiple cores.

Try to upgrade :)

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1  
5.0 definitely uses several threads. the problem here is table lockup –  Javier Jan 8 '11 at 12:31
1  
5.0 has lot of performances issues in comparison with the last versions, it's from Dec 2005... –  Kedare Jan 8 '11 at 17:52
    
We are working on migrating our production machines to the cloud (similar to Amazon's cloud servers). The version of mysql that we have installed on the machine that we use there is 5.1.48-log. Do you think we will have similar issues once we complete our migration? –  Joseph Yancey Jan 9 '11 at 1:36
    
It will be better, but if you can, try to take a look at the 5.5, it will provide a huge performance boost –  Kedare Jan 9 '11 at 12:16
1  
we did migrate the server and it has been a null issue since then. It looks like the newer version of MySQL did solve this issue (and create more...) –  Joseph Yancey Feb 4 '11 at 20:43
show 5 more comments

This seems an obvious effect of updating a single MyISAM table. The whole table is locked during writes.

Either use more tables, or switch those with heavy writes to InnoDB. Since the table engine choice is per table, not per database, you can choose what is best for each one.

Remember, MyISAM is fast for mostly-read tables, InnoDB is best for almost everything else.

Also, if you have a single table with so many writes, consider changing your architecture. check queue managers (to send those updates to a non-interactive task), or append-only engines (fast for logs or archives, if that's what you're doing), or a different kind of server for tight jobs (like an in-memory DB if you're doing a lot of temporary processing before writing final results to more persistent storage)

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