Both Windows and Linux are receiving significant security updates that can, in the worst case, cause performance to drop by half, to defend against a problem that as yet hasn't been fully disclosed.
Patches to the Linux kernel have been trickling in over the past few weeks. Microsoft has been testing the Windows updates in the Insider program since November, and it is expected to put the alterations into mainstream Windows builds on Patch Tuesday next week. Microsoft's Azure has scheduled maintenance next week, and Amazon's AWS is scheduled for maintenance on Friday—presumably related.
Since the Linux patches first came to light, a clearer picture of what seems to be wrong has emerged. While Linux and Windows differ in many regards, the basic elements of how these two operating systems—and indeed, every other x86 operating system such as FreeBSD and macOS—handle system memory is the same, because these parts of the operating system are so tightly coupled to the capabilities of the processor.