On Wed, Nov 01, 2017 at 05:59:27PM +0900, Byungchul Park wrote: > On Tue, Oct 31, 2017 at 04:10:24PM +0100, Peter Zijlstra wrote: > > On Tue, Oct 31, 2017 at 03:58:04PM +0100, Michal Hocko wrote: > > > On Tue 31-10-17 15:52:47, Peter Zijlstra wrote: > > > [...] > > > > If we want to save those stacks; we have to save a stacktrace on _every_ > > > > lock acquire, simply because we never know ahead of time if there will > > > > be a new link. Doing this is _expensive_. > > > > > > > > Furthermore, the space into which we store stacktraces is limited; > > > > since memory allocators use locks we can't very well use dynamic memory > > > > for lockdep -- that would give recursive and robustness issues. > > I agree with all you said. > > But, I have a better idea, that is, to save only the caller's ip of each > acquisition as an additional information? Of course, it's not enough in > some cases, but it's cheep and better than doing nothing. > > For example, when building A->B, let's save not only full stack of B, > but also caller's ip of A together, then use them on warning like: Like said; I've never really had trouble finding where we take A. And for the most difficult cases, just the IP isn't too useful either. So that would solve a non problem while leaving the real problem. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
