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. Thanks Alex
