On 09/05/2021 04:55, Daniel Nebdal wrote:
On Thu, 6 May 2021 at 19:05, David Chisnall <thera...@freebsd.org> wrote:
[ Disclaimer: I work for Microsoft, but not on WSL and this is my own
opinion ]
(...)
David
Just as a counterpoint to Rozhuk's take, that all sounds sensible
enough to me - FreeBSD would probably gain more from this than MS.
So the WSL2 TODO would be something like this:
* Ballooning driver. Seems like a proof of concept would be doable
enough - could you model it as an unkillable task (userland or kernel)
that wants to allocate a lot of memory, and anything it gets it hands
back to the host?
There's an in-tree Xen balloon driver that works in this way: it
allocates pages of memory from the kernel and then returns them to the
hypervisor.
It appears that Hyper-V actually supports two kinds of dynamic memory,
the balloon interface and a mechanism based on hotplug. The balloon
mechanism effectively defines a maximum amount of physical memory and
lets the guest return some of it. The hotplug mechanism boots with a
smaller amount of memory but can dynamically add and remove physical
memory. I don't know which is used in WSL2.
* Some sort of boot support. Maybe as a shim that chainloads an
unmodified kernel? Probably finicky, but also self-contained.
To start, you could kexec the FreeBSD kernel from a minimal Linux install.
* File systems. Is / also 9p-over-HyperV-channels? If so that's kind
of crucial and perhaps the hardest part.
I think WSL2 provides a block device for /, which is why Linux-native
filesystem performance is faster than WSL1. It would be great to have a
ZFS image instead of ext4 here!
Oh, and how does the terminal work? You support multiple ttys, so I
guess it's not straight emulated serial?
I believe that WSL2 uses SSH connections, rather than exposing the
serial terminal.
David
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