Re: [2.4.17/18pre] VM and swap - it's really unusable

Robert Love
2002-01-08T21:44:16Z

On Tue, 2002-01-08 at 16:24, Rik van Riel wrote:

> So what exactly _is_ the difference between an explicit
> preemption point and a place where we need to explicitly
> drop a spinlock ?

In that case nothing, except that when we drop the lock and check it is
the earliest place where preemption is allowed. In the normal scenario,
however, we have a check for reschedule on return from interrupt (e.g.
the timer) and thus preempt in the same manner as with user space and
that is the key.

> > Future work would be to look into long-held locks and see what we can
> > do.
>
> One thing we could do is download Andrew Morton's patch ;)

That is certainly one option, and Andrew's patch is very good.
Nonetheless, I think we need a more general framework that tackles the
problem itself. Preemptible kernel does this, yields results now, and
allows for greater return later on.

Robert Love