Are you saying you run the VMs in zram? When writing the article for the magazine, that was the only use I could think of. I realize that the data is compressed, once it goes into the zram block device, but it seems to me that for ordinary desktop use, it just takes away from available RAM. Especially if you have a large swap disk partition. And when my test PC only had 320MB to begin with, 25% of that was going to zram.
It's the same with my other older PC that has 512MB of RAM. I've been running the previous Bonsai on it for 2 or 3 months now, and it's super quick for the hardware specs. But, like I said, I disabled zram on that one, too.
djohnston, it does not take ram away. You ram is still there. But 25% (with the actual configuration) is compressed under the shape of a block device. But for the user this is transparent, you don't see it, you don't feel it.
I don't use the vbox machines in ZRAM. I use the vbox machines in my PCLinuxOS Openbox system where zram is enabled.
Look at this scheme:
___1 GB_|__1 GB__
So above it represents 2 GB memory installed.
Now with ZRAM:
___1 GB_|__1 GB__-zram-
the zram block device is compressed ram which is added to memory. *added*.
The 25% is a mathematical formula to calculate the size the block device will have. It is not retrieved from the total amount of RAM.
Let's say for an image, clothes that you just washed and which are full with water. You have them in a small bucket. But you have more washed clothes that you need to put in this bucket. Squeeze the clothes. Now they fit in. So you can have more clothes in the same bucket (more potential ram is available in the actual given memory space).
Next, I will try to add zram in a KDE4 machine in my system, to see if that works faster... In my Dell P4 with 1 GB ram, and cpu 2.8 Ghz, trying to use KDE4 is a real pain !
PS: you can have a large swap partition, which can be useful if you use hibernation. The datas stored in memory in ram, be it in zram will always be available faster than the datas stored in swap disk. This is a fact, when the swap partition starts to be used during a Xsession, all becomes slow in the screen, and you can wait for several seconds or more before a simple click to open a file, for example, brings the display of the given file.