Where does the memory allocated by Hyper-V go to the virtual machine?

Question

linux

Installed on Hyper-V Debian 9, specified dynamically allocated RAM. I use only the console, the graphical shell is turned off. And, suddenly, this virtual machine began to consume under 12 GB of RAM. Ok, limited to 4GB and restarted. But again, the maximum is allocated to the RAM, but at the same time there is such a free output:

[email protected]:~$ free
              total        used        free      shared  buff/cache   available
Mem:         935616      331624      406928       24672      197064      442748
Swap:      19529724           0    19529724

Explain, pls, why is that?

Answer 1

3 years had intimacy in Linux under hyper-in - my conclusion is that graphical shells eat up to the stop, regardless of the need.
only a bare installation, without GUI components initially, the same debian, shows a modest expense for real needs,
I will especially note KDE (in any distribution), everything is not so catastrophic here, but it still doesn’t look like the realism of Windows guests. KDE eats less in reserve, and gives more easily when not needed .. (probably QT architecture features) however, all the poles evaporate when we install a lot of GTK-based applications and actively exploit them
well, subjective observation - it seems that with the installation of the latest kernels, the situation is slightly improving. I don’t know for sure, but maybe the MS is slowly contributing, improving guest modules for hyper-v (and there are those in the kernel for sure, I was looking for info at one time, starting from 3. something there, guest modules for hyper-v in the Linux kernel out of the box ))
ps in the end, I settled on virtualbox - yes, there is no dynamic memory allocation ( upd but there is a funny effect, from the win 10 free memory "compression" mechanism, the illusion of dynamic allocation returns, in VMWare the same effect), but I mastered the presentation physical disks, well, the main bun is an easy forwarding of all kinds of USB devices. in terms of graphics - VMWare will be cooler, but in firmware, and it is paid (and I avoid piracy)
my personal conclusion is that for mock-up servers it’s hyper-to-cool, but you can also master containers then, and for a variety of experimentation with Linux guests, under Windows, virtual box still comes out more convenient
pps, but of course, for Windows guests under a Windows host - hyper - out of competition