How could I copy the RAM of a running application, save it, and reload it into RAM later on?

Question

I play modded Minecraft a fair bit. One downside to that is it takes a lot of time for all the mods to compile whenever I launch Minecraft. It can take around 15 minutes or so, which is too much time in my opinion. When a computer is running applications, everything it does is based off of inputs and data in RAM. I'm fairly certain that if one was to copy the RAM of their computer at a point in time and put that data back into RAM at another time, the computer would return to its former state. Though things may break down if the data in RAM doesn't actually agree with the data on the hard drive(like if windows explorer was open in the loaded RAM and showed files and folders which may not really be there on the hard drive).

I think it might be possible to copy the RAM data of an application(in my case a few GB of RAM after everything compiles and loads). I also think that if it were to be inserted back into the RAM at a later time, the application would appear already loaded without waiting for code to compile. How would I go about doing this? I think it's similar to save-state loading in emulators.

Answer 1

I'm fairly certain that if one was to copy the RAM of their computer at a point in time and put that data back into RAM at another time, the computer would return to its former state.

This is very perceptive of you; and this is precisely what happens when a computer "hibernates" [1]. You are also correct that unless the total state of RAM is saved and restored, or if the computer is allowed to operate in between the store and the restore, odd things are very likely to happen.

It is conceivable to store / restore the RAM state for a single application, but this would be a complex operation, and even with 25+ years of a career in IT, I have not heard of an application that can do this.

... Except for Phil Brubaker's comment, which mentions virtual machines. If you run Minecraft inside a virtual machine running on your physical machine, you can do just as Phil mentions : store and restore the running state of the VM at any point -- say, at the end of a Minecraft session. 'Snapshots' (again, as Phil mentions) are how this is done.

(VM applications might offer a 'suspend' feature, and while this might in some details be different from that VM application's 'snapshot' feature, the effect is the same, and it's just like hibernation for a physical machine : the running state (i.e., the contents of RAM and some details of what the CPU is doing at that exact moment) are saved to disk, and can be restored later to bring the VM back to exactly where it was at the point it was snapshot-ed / suspended.)

So I'd recommend a web search for "virtual machine applications for [fill in your operating system here]". VMWare and VirtualBox will be top hits; there will be others, depending on your operating system and such.

[1] Note that "sleeping" is different: in sleep, only some components are shut down, such as the hard drive, which is normally always spinning, whether or not it's actually reading/writing data. So sleep is a partial shutdown to save energy. Hibernation is a longer-term, very low power mode.