Re: RFC: pageable kernel-segments

Albert D. Cahalan
2001-04-17T23:58:28Z

H. Peter Anvin writes:
> By author: "Heusden, Folkert van" <f.v.heusden@ftr.nl>

>> Would anyone be intrested (besides me) in a kernel which can page
...
>> Certain parts of drivers could get the __pageable prefix or so

> VMS does this. It at least used to have a great tendency to crash
> itself, because it swapped out something that was called from a driver
> that was called by the swapper -- resulting in deadlock. You need
> iron discipline for this to work right in all circumstances.
>
> Second, it makes it quite hard to know what operations can cause a
> task to sleep, since any reference to paged-out memory can require a
> page-in and the associated schedule. You almost need pointer
> annotation in order for this to be safe.

It wouldn't be nearly so dangerous to page from compressed
data in memory. The memory could be ROM.