Linus Torvalds wrote: >> IIRC, the present bit is ignored in the magic 4-entry PGD. All entries >> have to be present.
On Thu, Nov 15, 2007 at 02:42:46PM -0800, H. Peter Anvin wrote: > This is true, although you could point a PGD to an all-zero page if you > really wanted to. You have to re-load CR3 after modifying the top-level > entries. There may be bigger fish to fry in terms of per-process overhead, if you're trying to cut that down. The trouble with trying to address some of those is that there is mutual antagonism between compactness and expansibility in the process address space layout, so you'll end up instantiating a lot more than you want barring some sort of provision for a compact address space layout. Pagetable sharing is a far more powerful resource scalability method, though it also needs cooperation in user address space layout to reap its gains. There are other overheads, of course, though they're more typically per-something besides processes. -- wli - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
