Reduce Linux VPS/VM guest memory usage

Published April 6th, 2009 by Paul De Audney

Reducing the memory usage in your VPS/VM can be a great way to free up some resources to handle more requests, users or some other metric of win.

By default at Anchor we provision our Red Hat & Cent OS VPS servers with a trim memory usage profile by disabling a lot of unneeded services at install time. We do this by using Trogdor (our hardware/software burninator) and Puppet.

So just what services do we disable, if they exist on the new VPS?

  • gpm
  • netfs
  • pcmcia
  • sgi_fam
  • yum-updatesd
  • pcscd
  • rhnsd
  • xfs
  • hald
  • hcid or sdpd
  • hpiod or hpssd.py
  • dbus-daemon
  • cupsd

You can also reap performance gains by changing how you serve content. For example you can use a cut down high performance web server (nginx or lighttpd) to serve all static content, such as images. Then use an Apache process to handle your dynamic requests.

Tuning Apache is deserving of an article all to itself, however some hard and fast rules are:

  • Disable all unnecessary modules.
  • Work out the per process memory usage, and set your max clients to a suitable number taking into account the available memory and other system daemons.
  • Disable htaccess if you do not need it.

PHP is much the same as Apache, disable what you do not need. This goes for any service or application with many optional components.

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Winning the war on PHP memory leakage

Published November 18th, 2008 by Barney Desmond

One of our dedicated server customers recently had a problem with the machine keeling over and dying for a few days in a row, for no apparent reason. This necessitated a remote reboot of the server to get it running again (we cut the power to both power supplies for a few seconds). The immediate suspicion was faulty hardware, but this should rarely be the case as we put our hardware through a thorough “burn in” period before it’s ever deployed. In addition to this, it was happening pretty regularly in the middle of the day.

After spotting this pattern, a quick look at our trending graphs showed us the problem very clearly. The machine was steadily using all available physical memory. Once this ran out, the system starts pushing data off to swapspace, which is on the disks. Once this runs out the OS simply has no more memory to give. It’ll start killing off processes in a desperate attempt to reclaim some memory, but this is rarely successful.

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