Re: [RFC PATCH 0/7] Forward merging entries and other VM shenanigans

[Sergey Bugaev]

Hello,

On Wed, Aug 30, 2023 at 2:16 AM Samuel Thibault <samuel.thibault@gnu.org> wrote:
> Just to make sure, may your work be affected by this?
>
> https://lists.gnu.org/archive/html/bug-hurd/2017-10/msg00011.html

Yes, I learned about that patch just after having sent mine.

> We had a patch in Debian that was disabling the coalescing because it
> could potentially coalesce areas not to be swappable (such as IDE write
> buffers) with swappable areas.

Not that I have any idea how IDE drivers work, but that patch sounds
rather pointless, since that very 'if' condition already checks for
the vm_entry being wired (= not swappable), and doesn't coalesce in
that case. Also, according to [0], that patch fixed nothing at the
time. So it should be safe to just drop it, which I see you have
already done.

[0]: https://mail.gnu.org/archive/html/bug-hurd/2017-10/msg00013.html

Related: I hacked up vm-object-create (the ramdisk replacement that
exposes the original pages instead of copying to kmalloc memory). I
haven't quite tested it because libstore doesn't support specifying
memobj port name on the command line, and I haven't gotten around to
implementing that. Would you still be interested in reviewing /
testing those patches, and eventually using it in Debian instead of
ramdisk? It would be great if Richard could review it too, since it
touches some of the vm_page things that I don't really understand.

Sergey