Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: Note describing poor dcache utilization under high memory pressure | Date | Tue, 29 Jan 2002 23:53:04 +0100 |
| |
On January 29, 2002 10:50 pm, Linus Torvalds wrote: > On Tue, 29 Jan 2002, Oliver Xymoron wrote: > > > > I don't think read-only for the tables is sufficient if the pages > > themselves are writable. > > At least on x86, the WRITE bit in the page directory entries will override > any bits int he PTE. In other words, it doesn't make the page directory > entries thmselves unwritable - it makes the final pages unwritable.
Ah, didn't know that.
> Which are exactly the semantics we want.
Yes. This feature might be useful to grab back a few cycles at the expense of some extra complexity. It is not however, a fundamental change to my algorithm, just a decoration of it. It's also possible that the cost of the resulting extra fault will wipe out the (small) saving of setting pte entries RO in the average case.
It's likely there are architectures where this won't work, and just not doing this optimization is the correct approach.
-- Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |