So to enable it, do the following:
Install ROM Manager trough market.
Start ROM Manager and select the first option "Flash ClockworkMod Recovery".
Turn off your device.
Turn on device with volume down pressed.
Press volume down, selection will switch to RECOVERY then press power button.
At the black screen with red triangle press volume up and power button.
Press volume down, selection will switch to Apply sdcard:update.zip and then press power button.
Open a console, navigate to the android SDK tools folder.
Type "adb mount /system", without the quotes doh!
Type "adb shell".
At the shell copy paste the following commands one by one and press enter after pasting them.
echo "#!/system/bin/sh" > /system/etc/init.d/05userinit
echo "swapon -a" >> /system/etc/init.d/05userinit
echo "/dev/block/mmcblk0p3 swap swap" >> /system/etc/fstab
chmod +x /system/etc/init.d/05userinit
chmod g-w /system/etc/init.d/05userinit
chmod o-w /system/etc/init.d/05userinit
chmod g-w /system/etc/fstab
chmod o-w /system/etc/fstab
Now you are back at the normal command prompt, type "adb reboot".
Device will reboot, when its done open a terminal and type "free".
It should show swap space allocated.
And with some programs in memory you can see swap being used:
total used free shared buffers
Mem: 407860 399940 7920 0 872
Swap: 249596 16596 233000
Total: 657456 416536 240920
Altho it was just using a small bit of swap, this obviously helps.
I was running two benchmarks, had maps open and a radio stream playing.
Quadrant showed my Desire rating at 559 while I was trying to get the phone to actually USE the swap space ...
Btw this is my first Android phone, but I have a rich linux background since 1998. Let's try Android 2.2 as this would boost the benchmark quite notably I recon!