Re: Getting big areas of memory, in 2.3.x?

Rik van Riel
1999-12-09T20:39:45Z

On Thu, 9 Dec 1999, Kanoj Sarcar wrote:
> > Ingo Molnar wrote:
> > > hm, does anyone have any conceptual problem with a new
> > > allocate_largemem(pages) interface in page_alloc.c? It's not terribly hard
> > > to scan all bitmaps for available RAM and mark the large memory area
> > > allocated and remove all pages from the freelists. Such areas can only be
> > > freed via free_largemem(pages). Both calls will be slow, so should be only
> > > used at driver initialization time and such.
> >
> > Would this interface swap out user pages if necessary? That sort of
> > interface would be great, and kill a number of hacks floating around out
> > there.
>
> Swapping out user pages is not a sure shot thing unless Linux implements
> reverse maps, so that we can track which page is being used by which pte.
>
> Without rmaps, any possible solution will be quite costly, if not an
> outright hack, IMO.

Not only that, we would also need to make
sure that no kernel data pages are in the way.

This means we'll need both reverse maps and
a "real" zoned allocator. Not a 2.4 thing,
I'm afraid :(

Rik
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