On Thu 30-05-19 14:57:46, Yang Shi wrote: > Hi folks, > > > As what we discussed about page demotion for PMEM at LSF/MM, the demotion > should respect to the mempolicy and allowed mems of the process which the > page (anonymous page only for now) belongs to. cpusets memory mask (aka mems_allowed) is indeed tricky and somehow awkward. It is inherently an address space property and I never understood why we have it per _thread_. This just doesn't make any sense to me. This just leads to weird corner cases. What should happen if different threads disagree about the allocation affinity while working on a shared address space? > The vma that the page is mapped to can be retrieved from rmap walk easily, > but we need know the task_struct that the vma belongs to. It looks there is > not such API, and container_of seems not work with pointer member. I do not think this is a good idea. As you point out in the reply we have that for memcgs but we really hope to get rid of mm->owner there as well. It is just more tricky there. Moreover such a reverse mapping would be incorrect. Just think of a disagreeing yet overlapping cpusets for different threads mapping the same page. Is it such a big deal to document that the node migrate is not compatible with cpusets? -- Michal Hocko SUSE Labs
