2017-11-28 18:48 GMT+08:00 Michal Hocko <mhocko@xxxxxxxx>: > On Tue 28-11-17 11:37:23, Jan Kara wrote: >> On Mon 27-11-17 10:19:39, Michal Hocko wrote: >> > Andrew, >> > could you simply send this to Linus. If we _really_ need something to >> > prevent misconfiguration, which I doubt to be honest, then it should be >> > thought through much better. >> >> What's so bad about the warning? I think warning about such >> misconfiguration is not a bad thing per se. Maybe it should be ratelimited >> and certainly the condition is too loose as your example shows but in >> principle I'm not against it and e.g. making the inequality in the condition >> strict like: >> >> if (unlikely(bg_thresh > thresh)) >> >> or at least >> >> if (unlikely(bg_thresh >= thresh && thresh > 0)) >> >> would warn about cases where domain_dirty_limits() had to fixup bg_thresh >> manually to make writeback throttling work and avoid reclaim stalls which >> is IMHO a sane thing... > > If it generates false positives then it is more harmful than useful. And > even if it doesn't, what is the point? Do we check that other related > knobs are configured properly? I do not think so, we simply rely on > admins doing sane things. Not all admins are good at tuning this. I don't think every SE knows how to tune vm.dirty_background_bytes and vm.dirty_background_bytes. Only kernel experts could do that. At least this warning could help them to learn what happend instead of knowing nothing. > Otherwise we would have a lot of warnings like > that. They would be pain to maintain and I believe the additional value > is quite dubious. > -- -- 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>
