On 2013/7/12 18:37, Michal Hocko wrote: > On Fri 12-07-13 17:54:27, Li Zefan wrote: >> On 2013/7/12 17:29, Michal Hocko wrote: >>> On Fri 12-07-13 17:20:09, Li Zefan wrote: >>> [...] >>>> But if I read the code correctly, even no one registers a vmpressure event, >>>> vmpressure() is always running and queue the work item. >>> >>> True but checking there is somebody is rather impractical. First we >>> would have to take a events_lock to check this and then drop it after >>> scheduling the work. Which doesn't guarantee that the registered event >>> wouldn't go away. >>> And even trickier, we would have to do the same for all parents up the >>> hierarchy. >>> >> >> The thing is, we can forget about eventfd. eventfd is checked in >> vmpressure_work_fn(), while vmpressure() is always called no matter what. > > But vmpressure is called only for an existing memcg. This means that > it cannot be called past css_offline so it must happen _before_ cgroup > eventfd cleanup code. > > Or am I missing something? > Yeah. The vmpressure work item is queued if we sense some memory pressure, no matter if there is any eventfd ever registered. This is the point. -- 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>