mysql使用高VIRT内存和RES比较

有没有办法减少 VIRT 内存的使用？我不确定使用率如此之高的原因是什么。它也达到了12g。

使用 top 命令

Tasks: 348 total,   1 running, 344 sleeping,   0 stopped,   3 zombie
Cpu(s):  1.4%us,  0.2%sy,  0.0%ni, 98.3%id,  0.1%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:  39131036k total,  4522864k used, 34608172k free,   228124k buffers
Swap: 16764924k total,        0k used, 16764924k free,  1316196k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
26760 www-data  20   0  312m  39m 4292 S   11  0.1   0:01.84 /usr/sbin/apache2 -
27149 www-data  20   0  312m  38m 3760 S   11  0.1   0:00.34 /usr/sbin/apache2 -
27193 www-data  20   0  312m  39m 4984 S   11  0.1   0:00.90 /usr/sbin/apache2 -
 1103 mysql     20   0  9.8g 195m 8244 S    1  0.5   5:40.69 /usr/sbin/mysqld
27180 www-data  20   0     0    0    0 Z    1  0.0   0:00.47 [apache2] <defunct>
   66 root      20   0     0    0    0 S    0  0.0   0:00.23 [kworker/15:0]
 8037 ntp       20   0 31496 1588 1244 S    0  0.0   0:01.13 /usr/sbin/ntpd -p /
26676 www-data  20   0  332m  58m 3960 S    0  0.2   0:01.73 /usr/sbin/apache2 -
26737 www-data  20   0  290m  16m 3476 S    0  0.0   0:00.23 /usr/sbin/apache2 -
26738 www-data  20   0  312m  39m 4292 S    0  0.1   0:00.68 /usr/sbin/apache2 -
26772 www-data  20   0  289m  15m 3928 S    0  0.0   0:00.41 /usr/sbin/apache2 -
26883 www-data  20   0  312m  39m 4300 S    0  0.1   0:00.48 /usr/sbin/apache2 -
27150 www-data  20   0  284m 8372 1516 S    0  0.0   0:00.02 /usr/sbin/apache2 -
27154 www-data  20   0  312m  39m 3876 S    0  0.1   0:00.44 /usr/sbin/apache2 -
27191 www-data  20   0  329m  55m 3644 S    0  0.1   0:00.44 /usr/sbin/apache2 -
27222 webaau    20   0 17568 1636 1072 R    0  0.0   0:00.06 top
    1 root      20   0 24428 2388 1352 S    0  0.0   0:03.60 /sbin/init

我的.cnf

#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
#
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html

# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
[client]
port            = 3306
socket          = /var/run/mysqld/mysqld.sock

# Here is entries for some specific programs
# The following values assume you have at least 32M ram

# This was formally known as [safe_mysqld]. Both versions are currently parsed.
[mysqld_safe]
socket          = /var/run/mysqld/mysqld.sock
nice            = 0

[mysqld]
#
# * Basic Settings
#
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql
tmpdir          = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address            = 127.0.0.1
#
# * Fine Tuning
#
key_buffer              = 16M
max_allowed_packet      = 16M
thread_stack            = 192K
thread_cache_size       = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover         = BACKUP
max_connections        = 300
#table_cache            = 64
#thread_concurrency     = 10
#
# * Query Cache Configuration
#
query_cache_limit       = 1M
query_cache_size        = 64M

#added by SRTPL
# changed qauery_cache_size from 16M to 32
tmp_table_size          = 64M
max_heap_table_size     = 64M
table_cache             = 500
wait_timeout            = 900
interactive_timeout     = 900
#2880

#End of adding
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file        = /var/log/mysql/mysql.log
#general_log             = 1
#
# Error logging goes to syslog due to /etc/mysql/conf.d/mysqld_safe_syslog.cnf.
#
# Here you can see queries with especially long duration
#log_slow_queries       = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
#       other settings you may need to change.
#server-id              = 1
#log_bin                        = /var/log/mysql/mysql-bin.log
expire_logs_days        = 10
max_binlog_size         = 100M
#binlog_do_db           = include_database_name
#binlog_ignore_db       = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem



[mysqldump]
quick
quote-names
max_allowed_packet      = 16M

[mysql]
#no-auto-rehash # faster start of mysql but no tab completition

[isamchk]
key_buffer              = 16M

#
# * IMPORTANT: Additional settings that can override those from this file!
#   The files must end with '.cnf', otherwise they'll be ignored.
#
!includedir /etc/mysql/conf.d/

我遇到的另一个问题是实际内存使用率很高，尽管没有进程在使用内存。在 my.cnf 中进行了几次 tweeking 并重新启动后，实际内存的高使用率不再发生。

使用 ubuntu 12.04
5.5.22-0ubuntu1
Apache2.2.22
PHP 版本 5.3.10-1ubuntu3.1