On Mon 05-04-21 10:08:24, Tim Chen wrote: [...] > To make fine grain cgroup based management of the precious top tier > DRAM memory possible, this patchset adds a few new features: > 1. Provides memory monitors on the amount of top tier memory used per cgroup > and by the system as a whole. > 2. Applies soft limits on the top tier memory each cgroup uses > 3. Enables kswapd to demote top tier pages from cgroup with excess top > tier memory usages. Could you be more specific on how this interface is supposed to be used? > This allows us to provision different amount of top tier memory to each > cgroup according to the cgroup's latency need. > > The patchset is based on cgroup v1 interface. One shortcoming of the v1 > interface is the limit on the cgroup is a soft limit, so a cgroup can > exceed the limit quite a bit before reclaim before page demotion reins > it in. I have to say that I dislike abusing soft limit reclaim for this. In the past we have learned that the existing implementation is unfixable and changing the existing semantic impossible due to backward compatibility. So I would really prefer the soft limit just find its rest rather than see new potential usecases. I haven't really looked into details of this patchset but from a cursory look it seems like you are actually introducing a NUMA aware limits into memcg that would control consumption from some nodes differently than other nodes. This would be rather alien concept to the existing memcg infrastructure IMO. It looks like it is fusing borders between memcg and cputset controllers. You also seem to be basing the interface on the very specific usecase. Can we expect that there will be many different tiers requiring their own balancing? -- Michal Hocko SUSE Labs
