On Wed, 4 Apr 2007, Dan Aloni wrote: > > To refine that example, you could replace the file with a large anonymous > memory pool and a lot of swap space committed to it. In that case - with > no ZERO_PAGE, would the kernel needlessly swap-out the zeroed pages? > Perhaps it's an example too far-fetched to worth considering...
Nice point, not far-fetched, though I don't know whether it's worth worrying about or not. Yes, as things stand, the kernel will needlessly write them out to swap: because we're in the habit of marking a writable pte as dirty, partly to save the processor (how i386-centric am I being?) from having to do that work just after, partly because of some race too ancient for me to know anything about - do_no_page (though not the function in question here) says: * This silly early PAGE_DIRTY setting removes a race * due to the bad i386 page protection. But it's valid * for other architectures too. Maybe Nick will decide to not to mark the readfaults as dirty. 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/