On Fri, May 18, 2007 at 04:42:10PM +0100, Hugh Dickins wrote: > On Fri, 18 May 2007, Nick Piggin wrote: > > > > 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. > > > > However we don't have to let those 8 bytes go to waste: we can use them > > to store the virtual address of the page, which kind of makes sense for > > 64-bit, because they can likely to use complicated memory models. > > Sooner rather than later, don't we need those 8 bytes to expand from > atomic_t to atomic64_t _count and _mapcount? Not that we really need > all 64 bits of both, but I don't know how to work atomically with less.
Yeah, that would be a very good use of it. > (Why do I have this sneaking feeling that you're actually wanting > to stick something into the lower bits of page->virtual?) No, I just thought I would get even more flamed if I was just adding padding that wasn't even doing _anything_ :) I remembered Ken had a benchmark where page_address was slow, and the rest is history... - 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/
