Windows 10: Update channels - Torrent?

It is exactly the same. If a process has a lock on an object it will keep using it even if you replace that object for new processes.

 

It's more or less impossible to upgrade your OS (which would include a kernel upgrade) without rebooting. By definition, a new kernel has to be initialized, which is the definition of a reboot.

Microsoft has been working on less frequent reboots, but you will likely never see "reboot free" OS upgrades that replace the kernel and other core system files.

Here's how the "less frequent" reboots work. Microsoft detects which process has the file locked, and shuts that process down, then does the upgrade and optionally restarts it. Since the file is not locked, it can be replaced without restarting. This is something Microsoft has not traditionally done for personal OS's (they've worked pretty hard on Server OS's to make reboots less frequent, but still more often than most would like).

I say above "more or less impossible" because, there are very tricky techniques that can be used to replace a running kernel in-memory, but this is generally only used in very advanced situations that require 100% uptime for government purposes, and the tools that do this are very expensive.

 

Could be done with one reboot, no need for so many. Going from 9926 to 10041, it took 4 reboots.

 

I think this upgrade was a bit more involved, because of the new "smaller footprint" optimizations.

The reason for multiple reboots is typically because of "chicken or egg" scenarios. You need to get some piece of functionality into the OS for the setup program itself to use to finish the install...