Hello. I have some advise about patch desription and only nitpick about implementation. On Wed, Feb 14, 2024 at 05:56:20AM +0800, "Jan Kratochvil (Azul)" <jkratochvil@xxxxxxxx> wrote: > which are useful for userland to easily and performance-wise find out the > effective cgroup limits being applied. I think this is a weak reasoning for in-kernel implementation. It may be faster but how often do you need to read that limit? > Otherwise userland has to Userland is at loss when running inside cgroupns with limited ancestors out of the cgroupns. Thus I think this is the reason why kernel can provide such an effective value. (And be subject line of the commit, I think bringing up cgroup1 is misleading.) > For cgroup1 it was implemented by: > memcg: show real limit under hierarchy mode > https://github.com/torvalds/linux/commit/fee7b548e6f2bd4bfd03a1a45d3afd593de7d5e9 > Date: Wed Jan 7 18:08:26 2009 -0800 FTR, commits are usually referenced more concisely like fee7b548e6f2 ("memcg: show real limit under hierarchy mode") (the document Waiman linked previously has some tips how to get this from git). > +static int memory_max_effective_show(struct seq_file *m, void *v) > +{ > + unsigned long memory; > + struct mem_cgroup *mi; > + > + /* Hierarchical information */ > + memory = PAGE_COUNTER_MAX; > + for (mi = mem_cgroup_from_seq(m); mi; mi = parent_mem_cgroup(mi)) > + memory = min(memory, READ_ONCE(mi->memory.max)); root_mem_cgroup is never charged (thus limited), so you can terminate the iteration on !mem_cgroup_is_root(mi), one level earlier > +static int swap_max_effective_show(struct seq_file *m, void *v) > +{ > + unsigned long swap; > + struct mem_cgroup *mi; > + > + /* Hierarchical information */ > + swap = PAGE_COUNTER_MAX; > + for (mi = mem_cgroup_from_seq(m); mi; mi = parent_mem_cgroup(mi)) > + swap = min(swap, READ_ONCE(mi->swap.max)); ditto HTH, Michal
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