Hi.
Matthew Garrett wrote:
On Thu, Feb 21, 2008 at 09:45:02AM +1100, Nigel Cunningham wrote:
- people keep talking about hibernating to an ext3 fs mounted on fuse as
a limitation of the freezer. To do that with kexec, you're still going
to have to bmap the ext3 fs and pass the block list (in which case we
can also do it without kexec) or umount all the ext3/fuse part and
remount in the kexec'd kernel. Sort of defeats the purpose, doesn't it?
No, with a freezer-based model you can basically *never* suspend to
anything related to FUSE or a userspace USB device or anything involving
userspace iSCSI initiators or whatever. Sure, there are cases where
moving away from the current model doesn't buy you anything, but that
doesn't mean that the current model is a good thing. It's not. The
freezer is a fundamentally broken concept.
Putting drivers and filesystems in userspace is the fundamentally broken
concept. Not just when it comes to the freezer. The whole idea is
inherently racy. You can draw silly diagrams about how the freezer
supposedly works in LCA slides and spread FUD as much as you like. In
the end, though, it's not nearly as hit-and-miss as you say, and
replacing the freezer with a kexec based freezer is only going to create
as many problems as it removes.
I also wonder about how much of a pain it's going to be setting up
userspace for this kexec'd kernel. Will you need a separate partition
just for it? If not, will the userspace be loaded into memory all the
time (more memory wasted for normal use), or loaded from ordinary
partitions at kexec time (how to do safely? - more info to transfer
between kernels?).
You're looking at a tiny amount of memory when compared to current
systems. It's really not a problem.
Please, quantify 'tiny'. In embedded, 5MB can be too much. I've worked
on embedded solutions. I'm not pulling problems out of thin air.
Regards,
Nigel
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