[OSM-dev] Reducing size on mediawiki server

[Nick Hill]

Given we have trouble with services quitting on mediawiki, presumably through an 
out of memory condition on the virtual server instance, anything we can do to 
reduce the memory footprint of the services supporting the wiki should improve 
reliability.

MySQL appears by far the hungriest service, so should get first attention.

According to top:
   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
  1483 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.10 mysqld
  1489 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.00 mysqld
  1490 mysql     18   0 54032  24m 4992 S  0.0 10.7   0:00.00 mysqld
  1491 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.00 mysqld
  1492 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.01 mysqld
  1493 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.01 mysqld
  1502 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.00 mysqld
  1503 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.00 mysqld
  1506 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.01 mysqld
  1568 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.05 mysqld
  1573 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.87 mysqld
  1817 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.26 mysqld
  1898 mysql     15   0 54032  24m 4992 S  0.0 10.7   0:00.25 mysqld

I notice the mediawiki databases are set to innodb. I understand that by 
disabling innodb and instead using myisam, the mysql threads can be made much 
lighter.

I understand that innodb has perhaps finer grained locking than myisam which can 
often make innodb perform better tan MyISAM.

Has anyone comparative experience using MyISAM vs Innodb on memory restricted 
servers?