On Wed, 4 Apr 2007, Nick Piggin wrote: > On Fri, Mar 30, 2007 at 04:40:48AM +0200, Nick Piggin wrote: > > > > Well it would make life easier if we got rid of ZERO_PAGE completely, > > which I definitely wouldn't complain about ;)
Yes, I love this approach too. > > So, what bad things (apart from my bugs in untested code) happen > if we do this? We can actually go further, and probably remove the > ZERO_PAGE completely (just need an extra get_user_pages flag or > something for the core dumping issue). Some things will go faster (no longer needing a separate COW fault on the read-protected ZERO_PAGE), some things will go slower and use more memory. The open question is whether anyone will notice those regressions: I'm hoping they won't, I'm afraid they will. And though we'll see each as a program doing "something stupid", as in the Altix case Robin showed to drive us here, we cannot just ignore it. > > Shall I do a more complete patchset and ask Andrew to give it a > run in -mm? I'd like you to: I didn't study the fragment below, it's really all uses of the ZERO_PAGE that I'd like to see go, then we see who shouts. It's quite likely that the patch would have to be reverted: don't bother to remove the allocations of ZERO_PAGE in each architecture at this stage, too much nuisance going back and forth on those. Leave ZERO_PAGE as configurable, default off for testing, buried somewhere like under EMBEDDED? It's much more attractive just to remove the old code, and reintroduce it if there's a demand; but leaving it under config would make it easy to restore, and if there's trouble with removing ZERO_PAGE, we might later choose to disable it at the high end but enable it at the low. What would you prefer? 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/
