Mmmm blog.

There are many reports across the web of OS X’s poor memory management, and up until yesterday, I had been suffering a lot because of it. However, finally, I’ve found the the cure! Something which I thought I would never do: disable swap.

What is “poor memory management” exactly?

In Linux, when physical memory is used up, swap starts getting used. However in Mac OS X (and Windows too), memory will be paged to disk even when there is free or inactive memory — and this sucks.

The solution: turn off paging to disk.

If you have enough memory to run all your day-to-day applications (I have 4GB), you can turn off the paging daemon to prevent OS X from paging anything to disk. For me, this has meant less disk thrashing and more responsive applications.

Turning off paging is something I thought I’d never do. In the past, I was completely against it as I trusted memory managers to make good decisions. However, since using Mac OS X 10.6, I no longer feel this way.

Here’s how you do it:

Paging is handled by a daemon called dynamic_pager. Turn this off with launchctl:

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.dynamic_pager.plist

Then, reboot:

sudo shutdown -r now

When the system boots back up, you can free some disk space by removing paging files:

sudo rm -f /private/var/vm/swapfile*

After this you’ll notice a lot more memory becomes “wired”, and memory is still marked “inactive” but it is freed straight away when other applications need it.