On Mon, Jan 27, 2020 at 09:34:35AM -0800, Roman Gushchin wrote: > To prepare for per-object accounting of slab objects, let's introduce > __mod_lruvec_memcg_state() and mod_lruvec_memcg_state() helpers, > which are similar to mod_lruvec_state(), but do not update global > node counters, only lruvec and per-cgroup. > > It's necessary because soon node slab counters will be used for > accounting of all memory used by slab pages, however on memcg level > only the actually used memory will be counted. The free space will be > shared between all cgroups, so it can't be accounted to any > specific cgroup. Makes perfect sense. However, I think the existing mod_lruvec_state() has a bad and misleading name, and adding to it in the same style makes things worse. Can we instead rename lruvec_state to node_memcg_state to capture that it changes all levels. And then do the following, clean API? - node_state for node only - memcg_state for memcg only - lruvec_state for lruvec only - node_memcg_state convenience wrapper to change node, memcg, lruvec counters You can then open-code the disjunct node and memcg+lruvec counters. [ Granted, lruvec counters are never modified on their own - always in conjunction with the memcg counters. And frankly, the only memcg counters that are modified *without* the lruvec counter-part are the special-case MEMCG_ counters. It would be nice to have 1) a completely separate API for the MEMCG_ counters; and then 2) the node API for node and 3) a cgroup API for memcg+lruvec VM stat counters that allow you to easily do the disjunct accounting for slab memory. But I can't think of poignant names for these. At least nothing that would be better than separate memcg_state and lruvec_state calls. ]
