On Thu 07-05-20 09:33:01, Shakeel Butt wrote: > Currently the reclaim of excessive usage over memory.high is scheduled > to run on returning to the userland. The main reason behind this > approach was simplicity i.e. always reclaim with GFP_KERNEL context. > However the underlying assumptions behind this approach are: the current > task shares the memcg hierarchy with the given memcg and the memcg of > the current task most probably will not change on return to userland. > > With the remote charging, the first assumption breaks and it allows the > usage to grow way beyond the memory.high as the reclaim and the > throttling becomes ineffective. > > This patch forces the synchronous reclaim and potentially throttling for > the callers with context that allows blocking. For unblockable callers > or whose synch high reclaim is still not successful, a high reclaim is > scheduled either to return-to-userland if current task shares the > hierarchy with the given memcg or to system work queue. > > Signed-off-by: Shakeel Butt <[email protected]>
Acked-by: Michal Hocko <[email protected]> I would just make the early break a bit more clear. [...] > @@ -2600,8 +2596,23 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t > gfp_mask, > schedule_work(&memcg->high_work); > break; > } > - current->memcg_nr_pages_over_high += batch; > - set_notify_resume(current); > + > + if (gfpflags_allow_blocking(gfp_mask)) > + reclaim_over_high(memcg, gfp_mask, batch); > + /* * reclaim_over_high reclaims parents up the * hierarchy so we can break out early here. */ > + if (page_counter_read(&memcg->memory) <= > + READ_ONCE(memcg->high)) > + break; > + /* > + * The above reclaim might not be able to do much. Punt > + * the high reclaim to return to userland if the current > + * task shares the hierarchy. > + */ > + if (current->mm && mm_match_cgroup(current->mm, memcg)) > { > + current->memcg_nr_pages_over_high += batch; > + set_notify_resume(current); > + } else > + schedule_work(&memcg->high_work); > break; > } > } while ((memcg = parent_mem_cgroup(memcg))); > -- > 2.26.2.526.g744177e7f7-goog > -- Michal Hocko SUSE Labs
