On 10/23/19 4:31 PM, Michal Hocko wrote: > On Wed 23-10-19 15:48:36, Vlastimil Babka wrote: >> On 10/23/19 3:37 PM, Michal Hocko wrote: >>> >>> But those wouldn't really help to prevent from the lockup, right? >> >> No, but it would perhaps help ensure that only people who know what they >> are doing (or been told so by a developer e.g. on linux-mm) will try to >> collect the data, and not some automatic monitoring tools taking >> periodic snapshots of stuff in /proc that looks interesting. > > Well, we do trust root doesn't do harm, right? Perhaps too much :) >>> Besides that who would enable that config and how much of a difference >>> would root only vs. debugfs make? >> >> I would hope those tools don't scrap debugfs as much as /proc, but I >> might be wrong of course :) >> >>> Is the incomplete value a real problem? >> >> Hmm perhaps not. If the overflow happens only for one migratetype, one >> can use also /proc/buddyinfo to get to the exact count, as was proposed >> in this thread for Movable migratetype. > > Let's say this won't be the case. What is the worst case that the > imprecision would cause? In other words. Does it really matter whether > we have 100k pages on the free list of the specific migrate type for > order or say 200k? Probably not, it rather matters for which order the count approaches zero.
