On Wed, 4 Apr 2007, Andrea Arcangeli wrote: > On Wed, Apr 04, 2007 at 08:35:30AM -0700, Linus Torvalds wrote: > > Anyway, I'm not against this, but I can see somebody actually *wanting* > > the ZERO page in some cases. I've used the fact for TLB testing, for > > example, by just doing a big malloc(), and knowing that the kernel will > > re-use the ZERO_PAGE so that I don't get any cache effects (well, at least > > not any *physical* cache effects. Virtually indexed cached will still show > > effects of it, of course, but I haven't cared). > > Ok, those cases wanting the same zero page, could be fairly easily > converted to an mmap over /dev/zero
No, MAP_SHARED mmap of /dev/zero uses shmem, which allocates distinct pages for this (because in general tmpfs doesn't know if a readonly file will be written to later on), and MAP_PRIVATE mmap of /dev/zero uses the zeromap stuff which we were hoping to eliminate too (though not in Nick's initial patch). Looks like a job for /dev/same_page_over_and_over_again. > (without having to run 4k large mmap syscalls or nonlinear). You scared me, I made no sense of that at first: ah yes, repeatedly mmap'ing the same page can be done those ways. Hugh - 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/
