On Mon, Dec 19, 2022 at 09:08:31PM +0100, Borislav Petkov wrote: > On Mon, Dec 19, 2022 at 09:00:26AM -0600, Michael Roth wrote: > > We implemented this approach for v7, but it causes a fairly significant > > performance regression, particularly for the case for npages > 1 which > > this change was meant to optimize. > > > > I still need to dig in a big but I'm guessing it's related to flushing > > behavior. > > Well, AFAICT, change_page_attr_set_clr() flushes once at the end. > > Don't you need to flush when you modify the direct map? > > > It would however be nice to have a set_direct_map_default_noflush() > > variant that accepted a 'npages' argument, since it would be more > > performant here and also would potentially allow for restoring the 2M > > direct mapping in some cases. Will look into this more for v8. > > set_pages_direct_map_default_noflush() > > I guess. > > Although the name is a mouthful so I wouldn't mind having those > shortened. I had a patch that just adds numpages parameter: https://lore.kernel.org/lkml/20201123095432.5860-4-rppt@xxxxxxxxxx/ The set_direct_map*() are not too widely used, so it's not a big deal to update all callers. > In any case, as long as that helper is properly defined and documented, > I don't mind. > > Thx. > > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette > -- Sincerely yours, Mike.
