On Thu, Mar 08, 2007 at 01:11:43PM +0100, Peter Zijlstra wrote: > On Thu, 2007-03-08 at 12:48 +0100, Miklos Szeredi wrote: > > > However this still leaves the non-linear reclaim (Nick pointed it out as > > > a potential DoS and other people have corroborated this). I have no idea > > > on that to do about that. > > > > OK, but that is a completely different problem, not affecting > > page_mkclean() or msync(). > > > > And it doesn't sound too hard to solve: when current algorithm doesn't > > seem to be making progress, then it will have to be done the hard way, > > searching for for all nonlinear ptes of a page to unmap. > > Ah, you see, but that is when you've already lost. > > The DoS is about the computational complexity of the reclaim, not if it > will ever come out of it with free pages.
If we really want to, we could limit it to mlock for !root. This is a reasonable way to solve the problem, and UML could fall back on vma emulated version if they didn't want to use mlock memory... Or we could limit the size/number of nonlinear vmas that could be created. But just quietly, I think there are probably a lot of other ways to perform a local DoS anyway ;) - 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/
