On Mon 30-01-17 09:12:10, Michal Hocko wrote: > On Fri 27-01-17 11:40:42, Theodore Ts'o wrote: > > On Fri, Jan 27, 2017 at 10:37:35AM +0100, Michal Hocko wrote: > > > If this ever turn out to be a problem and with the vmapped stacks we > > > have good chances to get a proper stack traces on a potential overflow > > > we can add the scope API around the problematic code path with the > > > explanation why it is needed. > > > > Yeah, or maybe we can automate it? Can the reclaim code check how > > much stack space is left and do the right thing automatically? > > I am not sure how to do that. Checking for some magic value sounds quite > fragile to me. It also sounds a bit strange to focus only on the reclaim > while other code paths might suffer from the same problem. > > What is actually the deepest possible call chain from the slab reclaim > where I stopped? I have tried to follow that path but hit the callback > wall quite early. > > > The reason why I'm nervous is that nojournal mode is not a common > > configuration, and "wait until production systems start failing" is > > not a strategy that I or many SRE-types find.... comforting. > > I understand that but I would be much more happier if we did the > decision based on the actual data rather than a fear something would > break down. ping on this. I would really like to move forward here and target 4.11 merge window. Is your concern so serious to block this patch? -- Michal Hocko SUSE Labs
