On Wed, Nov 27, 2019 at 5:17 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
>
> On Wed, Nov 27, 2019 at 4:54 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> >
> > On Tue 26-11-19 20:28:37, Yafang Shao wrote:
> > > There's one case that the processes in a memcg are all exit (due to OOM
> > > group or some other reasons), but the file page caches are still exist.
> > > These file page caches may be protected by memory.min so can't be
> > > reclaimed. If we can't success to restart the processes in this memcg or
> > > don't want to make this memcg offline, then we want to drop the file page
> > > caches.
> > > The advantage of droping this file caches is it can avoid the reclaimer
> > > (either kswapd or direct) scanning and reclaiming pages from all memcgs
> > > exist in this system, because currently the reclaimer will fairly reclaim
> > > pages from all memcgs if the system is under memory pressure.
> > > The possible method to drop these file page caches is setting the
> > > hard limit of this memcg to 0. Unfortunately this may invoke the OOM killer
> > > and generates lots of outputs, that should not happen.
> > > The OOM output is not expected by the admin if he or she wants to drop
> > > the cahes and knows there're no processes in this memcg.
> > >
> > > If memcg is not populated, we should not invoke the OOM killer because
> > > there's nothing to kill. Next time when you start a new process and if the
> > > max is still bellow usage, the OOM killer will be invoked and your new
> > > process is killed, so we can cosider it as lazy OOM, that is we have been
> > > always doing in the kernel.
> > >
> > > Fixes: b6e6edcf ("mm: memcontrol: reclaim and OOM kill when shrinking memory.max below usage")
> > > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > > Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> > > Cc: Michal Hocko <mhocko@xxxxxxxx>
> >
> > due to reasons explained repeatedly
> > Nacked-by: Michal Hocko <mhocko@xxxxxxxx>
> >
> > And I really find it highly annoying that you keep ignoring the review
> > feedback.
>
> I didn't ignore your feedback, pls. read my reply and commit log seriously.
> The reason I didn't accept your freeback is that your freeback is
> based on your wrong knowladge.
>
While Johannes really give me some useful feedback, Thanks Johannes !
Thanks
Yafang
