Messages in this thread | | | From | (Kanoj Sarcar) | Subject | Re: Getting big areas of memory, in 2.3.x? | Date | Thu, 9 Dec 1999 12:54:11 -0800 (PST) |
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> > 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 :( >
Well, at least in 2.3, kernel data (and page caches) are below 1G, which means there's a lot of memory possible out there with references only from user memory. Shm page references are revokable too. Of course, in 2.5, things will probably change.
Kanoj
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