Hello Michal, Michal Koutný <mkoutny@xxxxxxxx> writes: > Hello. > > On Wed, Oct 14, 2020 at 08:07:49PM +0100, Richard Palethorpe <rpalethorpe@xxxxxxxx> wrote: >> SLAB objects which outlive their memcg are moved to their parent >> memcg where they may be uncharged. However if they are moved to the >> root memcg, uncharging will result in negative page counter values as >> root has no page counters. > Why do you think those are reparented objects? If those are originally > charged in a non-root cgroup, then the charge value should be propagated up the > hierarchy, including root memcg, so if they're later uncharged in root > after reparenting, it should still break even. (Or did I miss some stock > imbalance?) I traced it and can see they are reparented objects and that the root groups counters are zero (or negative if I run madvise06 multiple times) before a drain takes place. I'm guessing this is because the root group has 'use_hierachy' set to false so that the childs page_counter parents are set to NULL. However I will check, because I'm not sure about either. > > (But the patch seems justifiable to me as objects (not)charged directly to > root memcg may be incorrectly uncharged.) > > Thanks, > Michal -- Thank you, Richard.
