High table_cache being ignored?

[Ben Sebborn]

Hi

I have recently increased our table_cache from 512 to 1024 as the number of opened_tables was growing quickly. I have checked and the table_cache variable is showing as 1024 on the running server.

However, since the change a strange result is occuring:

open_tables is at 53
opened_tables is at 28,000+

It seems as though it will not leave the tables in cache - any reason why this might be happening?

mysql> SHOW STATUS;
+--------------------------+------------+
| Variable_name | Value |
+--------------------------+------------+
| Aborted_clients | 136 |
| Aborted_connects | 2236 |
| Bytes_received | 212156771 |
| Bytes_sent | 4092141932 |
| Com_admin_commands | 52 |
| Com_alter_table | 8 |
| Com_analyze | 1 |
| Com_backup_table | 0 |
| Com_begin | 157 |
| Com_change_db | 49417 |
| Com_change_master | 0 |
| Com_check | 2 |
| Com_commit | 157 |
| Com_create_db | 0 |
| Com_create_function | 0 |
| Com_create_index | 0 |
| Com_create_table | 14 |
| Com_delete | 1105 |
| Com_delete_multi | 0 |
| Com_drop_db | 0 |
| Com_drop_function | 0 |
| Com_drop_index | 0 |
| Com_drop_table | 13 |
| Com_flush | 3 |
| Com_grant | 0 |
| Com_ha_close | 0 |
| Com_ha_open | 0 |
| Com_ha_read | 0 |
| Com_insert | 1384 |
| Com_insert_select | 11 |
| Com_kill | 0 |
| Com_load | 0 |
| Com_load_master_data | 0 |
| Com_load_master_table | 0 |
| Com_lock_tables | 0 |
| Com_optimize | 1 |
| Com_purge | 0 |
| Com_rename_table | 0 |
| Com_repair | 0 |
| Com_replace | 2976 |
| Com_replace_select | 0 |
| Com_reset | 0 |
| Com_restore_table | 0 |
| Com_revoke | 0 |
| Com_rollback | 0 |
| Com_savepoint | 0 |
| Com_select | 200405 |
| Com_set_option | 23343 |
| Com_show_binlog_events | 0 |
| Com_show_binlogs | 0 |
| Com_show_create | 23359 |
| Com_show_databases | 47 |
| Com_show_fields | 23900 |
| Com_show_grants | 0 |
| Com_show_keys | 28 |
| Com_show_logs | 0 |
| Com_show_master_status | 0 |
| Com_show_new_master | 0 |
| Com_show_open_tables | 0 |
| Com_show_processlist | 0 |
| Com_show_slave_hosts | 0 |
| Com_show_slave_status | 0 |
| Com_show_status | 90430 |
| Com_show_innodb_status | 90375 |
| Com_show_tables | 24888 |
| Com_show_variables | 23 |
| Com_slave_start | 0 |
| Com_slave_stop | 0 |
| Com_truncate | 0 |
| Com_unlock_tables | 0 |
| Com_update | 20409 |
| Com_update_multi | 0 |
| Connections | 48575 |
| Created_tmp_disk_tables | 8553 |
| Created_tmp_tables | 29965 |
| Created_tmp_files | 4 |
| Delayed_insert_threads | 0 |
| Delayed_writes | 0 |
| Delayed_errors | 0 |
| Flush_commands | 1 |
| Handler_commit | 0 |
| Handler_delete | 787 |
| Handler_read_first | 32987 |
| Handler_read_key | 192153862 |
| Handler_read_next | 598436805 |
| Handler_read_prev | 25 |
| Handler_read_rnd | 2533968 |
| Handler_read_rnd_next | 242537511 |
| Handler_rollback | 12 |
| Handler_update | 2431484 |
| Handler_write | 86859323 |
| Key_blocks_used | 124224 |
| Key_read_requests | 793838246 |
| Key_reads | 498713 |
| Key_write_requests | 19076102 |
| Key_writes | 7586 |
| Max_used_connections | 26 |
| Not_flushed_key_blocks | 0 |
| Not_flushed_delayed_rows | 0 |
| Open_tables | 103 |
| Open_files | 207 |
| Open_streams | 0 |
| Opened_tables | 28470 |
| Questions | 1499642 |
| Qcache_queries_in_cache | 29361 |
| Qcache_inserts | 87867 |
| Qcache_hits | 861188 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 112377 |
| Qcache_free_memory | 58494792 |
| Qcache_free_blocks | 1366 |
| Qcache_total_blocks | 60627 |
| Rpl_status | NULL |
| Select_full_join | 499 |
| Select_full_range_join | 0 |
| Select_range | 3390 |
| Select_range_check | 0 |
| Select_scan | 106457 |
| Slave_open_temp_tables | 0 |
| Slave_running | OFF |
| Slow_launch_threads | 0 |
| Slow_queries | 5 |
| Sort_merge_passes | 0 |
| Sort_range | 7226 |
| Sort_rows | 2882214 |
| Sort_scan | 32586 |
| Table_locks_immediate | 334615 |
| Table_locks_waited | 1 |
| Threads_cached | 20 |
| Threads_created | 27 |
| Threads_connected | 7 |
| Threads_running | 1 |
| Uptime | 168319 |
+--------------------------+------------+
133 rows in set (0.00 sec)


[mysqld]
skip-locking
skip-bdb
log_slow_queries
key_buffer=128M
join_buffer=2M
record_buffer=8M
read_buffer_size=2M

max_allowed_packet=1M
table_cache=1024
thread_stack=128K
sort_buffer=2M
net_buffer_length=8K
myisam_sort_buffer_size=4M
server-id= 1
thread_cache=50
thread_concurrency=2
max_connections=150
tmp_table_size=64M


query-cache-type = 1
query-cache-size = 98M
query_cache_limit = 1M
log-warnings