So getting a bit of systems administration housecleaning done. Have had a persistent memory issue on the server (LAMP, CentOS 6) likely due to poorly tuned Apache and mysql. The virtual server has 512MB RAM and I set a cron job to restart httpd twice daily to avoid dealing with the problem.
First, I looked at apache.
1. Check what MPM is in use (prefork vs worker)
– prefork MPM uses multiple child processes with one thread each.
– Each process handles one connection at a time and uses more memory.
– Good for non-thread-safe third party modules.
– worker MPM uses multiple child processes with many threads each.
– Each thread handles one connection at a time.
– Good for high-traffic, smaller memory footprint.
$ ./usr/sbin/apachectl -V | grep MPM Server MPM: Prefork -D APACHE_MPM_DIR="server/mpm/prefork"
2. Edit httpd.conf (/etc/httpd/conf/httpd.conf) so not configured to start too many servers, or have to many spare servers sitting around.
# prefork MPM # StartServers: number of server processes to start # MinSpareServers: minimum number of server processes which are kept spare # MaxSpareServers: maximum number of server processes which are kept spare # ServerLimit: maximum value for MaxClients for the lifetime of the server # MaxClients: maximum number of server processes allowed to start # MaxRequestsPerChild: maximum number of requests a server process serves
StartServers 1 MinSpareServers 1 MaxSpareServers 5 ServerLimit 25 MaxClients 25 MaxRequestsPerChild 3000
3. Edit my.cnf (/etc/my.cnf) for a low memory environment.
$ sudo vi /etc/my.cnf
[mysqld] key_buffer = 16K max_allowed_packet = 1M table_cache = 4 sort_buffer_size = 64K read_buffer_size = 256K read_rnd_buffer_size = 256K net_buffer_length = 2K thread_stack = 64K [mysqldump] quick max_allowed_packet = 16M [mysql] no-auto-rehash [isamchk] key_buffer = 8M sort_buffer_size = 8M [myisamchk] key_buffer = 8M sort_buffer_size = 8M [mysqlhotcopy] interactive-timeout
Now to see if it makes a difference.