Re: Back to the future.

Pavel Machek
2007-05-07T13:53:27Z

Hi!

> > The "let's stop all kernel threads" is superstition. It's the same kind of
> > superstition that made people write "sync" three times before turning off
> > the power in the olden times. It's the kind of superstition that comes
> > from "we don't do things right, so let's be vewy vewy quiet and _pray_
> > that it works when we are beign quiet".
>
> Side note: while I think things should probably *work* even with user
> processes going full bore while a snapshot it taken, I'll freely admit
> that I'll follow that superstition far enough that I think it's probably a
> good idea to try to quiesce the system to _some_ degree, and that stopping
> user programs is a good idea. Partly because the whole memory shrinking
> thing, and partly just because we should do the snapshot with hw IO queues
> empty.
>
> But I don't think it would necessarily be wrong (and in many ways it would
> probably be *right*) to do that IO queue stopping at the queue level
> rather than at a process level. Why stop processes just becasue you want
> to clean out IO queues? They are two totally different things!

Actually, I'd like to stop I/O queues; if there was easy way to do
that, I'll happily switch. Notice that we'll need to stop 'I/O queues'
of the char devices, too...
Pavel
--
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