Re: [RFC] 2.3/4 VM queues idea

Jamie Lokier
2000-05-26T17:02:08Z

Stephen C. Tweedie wrote:
> > That's ok. VA == vma->pgoff + page_offset. Move a vma and that's still
> > true. The ptes are found by looking at the list of all vmas referring
> > to all the address_spaces that refer to a page.
>
> And that is _exactly_ the problem --- especially with heavy mprotect()
> use, processes can have enormous numbers of vmas. Electric fence and
> distributed shared memory/persistent object stores are the two big,
> obvious cases here.

The stacked private address_spaces I described don't have to be shared
between address_spaces in a single mm. You can have one per vma --
that's simple but maybe wasteful. Or one per several vmas. When you
divide a single vma into zillions using mprotect(), you're free to split
off new spaces to limit the number of vmas per space.

-- Jamie

>
> --Stephen