On Fri, May 18, 2007 at 10:42:30AM +0100, David Howells wrote: > Nick Piggin <[EMAIL PROTECTED]> wrote: > > > I'd like to be the first to propose an increase to the size of struct page > > just for the sake of increasing it! > > Heh. I'm surprised you haven't got more adverse reactions. > > > If we add 8 bytes to struct page on 64-bit machines, it becomes 64 bytes, > > which is quite a nice number for cache purposes. > > Whilst that's true, if you have to deal with a run of contiguous page structs > (eg: the page allocator, perhaps) it's actually less efficient because it > takes more cache to do it. But, hey, it's a compromise whatever. > > In the scheme of things, if we're mostly dealing with individual page structs > (as I think we are), then yes, I think it's probably a good thing to do - > especially with larger page sizes.
Yeah, we would end up eating about 12.5% more cachelines for contiguous runs of pages... but that only kicks in after we've touched 8 of them I think, and by that point the accesses should be very prefetchable. I think the average of 75% more cachelines touched for random accesses is going to outweigh the contiguous batch savings, but that's just a guess at this point. - 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/