On Sat, Apr 18, 2020 at 6:45 AM Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> wrote: > > > > 在 2020/4/18 上午12:54, Michal Hocko 写道: > > On Fri 17-04-20 09:41:04, Shakeel Butt wrote: > >> On Fri, Apr 17, 2020 at 9:03 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > >>> > >>> On Fri 17-04-20 22:43:43, Alex Shi wrote: > >>>> This patch fold MEMCG_SWAP feature into kernel as default function. That > >>>> required a short size memcg id for each of page. As Johannes mentioned > >>>> > >>>> "the overhead of tracking is tiny - 512k per G of swap (0.04%).' > >>>> > >>>> So all swapout page could be tracked for its memcg id. > >>> > >>> I am perfectly OK with dropping the CONFIG_MEMCG_SWAP. The code that is > >>> guarded by it is negligible and the resulting code is much easier to > >>> read so no objection on that front. I just do not really see any real > >>> reason to flip the default for cgroup v1. Why do we want/need that? > >>> > >> > >> Yes, the changelog is lacking the motivation of this change. This is > >> proposed by Johannes and I was actually expecting the patch from him. > >> The motivation is to make the things simpler for per-memcg LRU locking > >> and workingset for anon memory (Johannes has described these really > >> well, lemme find the email). If we keep the differentiation between > >> cgroup v1 and v2, then there is actually no point of this cleanup as > >> per-memcg LRU locking and anon workingset still has to handle the > >> !do_swap_account case. > > > > All those details really have to go into the changelog. I have to say > > that I still do not understand why the actual accounting swap or not > > makes any difference for per per-memcg LRU. Especially when your patch > > keeps the kernel command line parameter still in place. > > > > Anyway, it would be much more simpler to have a patch that drops the > > CONFIG_MEMCG_SWAP and a separate one which switches the default > > beahvior. I am not saying I am ok with the later but if the > > justification is convincing then I might change my mind. > > > > Hi Shakeel & Michal, > > Thanks for all comments! > > Yes, we still need to remove swapaccount from cmdline and keep swap_cgroup.id > permanently. Just I don't know if this patch could fit into the details of > Johannes new solution. > > Anyway, I will send out v2 for complete memcg id record patch, just in case > if they are useful. > I would recommend waiting for Johannes patch series. The cleanup this patch is doing makes more sense to be part of Johannes's lrucare cleanup series. thanks, Shakeel
