On Tue 26-11-19 11:52:19, Yafang Shao wrote: > On Mon, Nov 25, 2019 at 10:42 PM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > > On Mon, Nov 25, 2019 at 03:21:50PM +0100, Michal Hocko wrote: > > > On Mon 25-11-19 22:11:15, Yafang Shao wrote: > > > > When there're no processes, we don't need to protect the pages. You > > > > can consider it as 'fault tolerance' . > > > > > > I have already tried to explain why this is a bold statement that > > > doesn't really hold universally and that the kernel doesn't really have > > > enough information to make an educated guess. > > > > I agree, this is not obviously true. And the kernel shouldn't try to > > guess whether the explicit userspace configuration is still desirable > > to userspace or not. Should we also delete the cgroup when it becomes > > empty for example? > > > > It's better to implement these kinds of policy decisions from > > userspace. > > > > There is a cgroup.events file that can be polled, and its "populated" > > field shows conveniently whether there are tasks in a subtree or > > not. You can use that to clear protection settings. > > Why isn't force_empty supported in cgroup2 ? There wasn't any sound usecase AFAIR. > In this case we can free the protected file pages immdiately with force_empty. You can do the same thing by setting the hard limit to 0. -- Michal Hocko SUSE Labs
