zlacker

What is your definition of free memory? If the system has read a lot of data, the page cache is probably occupying most of the RAM you consider free. Look at cache and standby counters.

I’ve noticed that windows can only evict data from the page cache at about 5 GB/s. I do not know if this zeros the memory or that would need to be done in the allocation path.

A couple years ago I tracked down a long pause while starting qemu on Linux to it zeroing the 100s of GB of RAM given to the VM as 1 GB huge pages.

These may or may not be big contributors to what you are seeing, depending on the VM’s RAM size.