Experiencing periodic slow session creation

[Keith Pierno]

Can anyone explain the process session create from the initial client connect through creation of user's session. Currently, I am seeing intermittent slow downs where a new connections hang for about 5 to 20 seconds. If you have an existing connection you are not affected but all new connections hang. There is no information to be found in the logs related to the issue. This is true of both local users and remote connections. We are well below our session limit and have skip-resolve-name set. Server is RHEL5 64bit with MySQL Server version: 5.0.45. The server has ample resources.

[root@xxxxx log]# cat /proc/meminfo | grep MemTotal
MemTotal: 34979304 kB

[root@xxxxx log]# cat /proc/cpuinfo | grep processor
processor : 0
processor : 1
processor : 2
processor : 3
processor : 4
processor : 5
processor : 6
processor : 7

[root@xxxxx log]# uptime
11:29:15 up 351 days, 1:39, 2 users, load average: 1.84, 2.04, 2.15

[root@xxxxx log]# cat /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1
max_connections=1600
wait_timeout=5
thread_cache_size=40

log-bin=mysql-bin
server-id=10
#binlog-ignore-db=mysql

skip-slave-start
skip-name-resolve

# adding this so that we can create a slave of this guy
log-slave-updates
replicate-same-server-id = 0

expire_logs_days = 7

max_allowed_packet = 16M

transaction-isolation =READ-UNCOMMITTED

query_cache_size= 1024M
long_query_time = 1
log_slow_queries
innodb_buffer_pool_size = 20000M
innodb_additional_mem_pool_size = 200M
innodb_file_per_table
innodb_log_file_size = 2000M
innodb_log_buffer_size = 8M


innodb_flush_method=O_DIRECT
innodb_flush_log_at_trx_commit = 2
key_buffer = 256M
table_cache = 250
sort_buffer_size = 128M
read_buffer_size = 128M
read_rnd_buffer_size = 512M


[mysql.server]
user=mysql
basedir=/var/lib


[mysqldump]
quick
max_allowed_packet = 16M


[mysqld_safe]
log=/var/log/mysqld.log
log-error=/var/log/mysqld.err
pid-file=/var/run/mysqld/mysqld.pid