Hello, cgroup1 (by function memcg1_stat_format) already contains two lines hierarchical_memory_limit %llu hierarchical_memsw_limit %llu which are useful for userland to easily and performance-wise find out the effective cgroup limits being applied. Otherwise userland has to open+read+close the file "memory.max" and/or "memory.swap.max" in multiple parent directories of a nested cgroup. 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 But for cgroup2 it has been missing so far, this is just a copy-paste of the cgroup1 code while changing s/memsw/swap/ as that is what cgroup1 vs. cgroup2 tracks. I have added it to the end of "memory.stat" to prevent possible compatibility problems with existing code parsing that file. Jan Kratochvil Signed-off-by: Jan Kratochvil (Azul) <jkratochvil@xxxxxxxx> mm/memcontrol.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 46d8d0211..2631dd810 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1636,6 +1636,8 @@ static inline unsigned long memcg_page_state_local_output( static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) { int i; + unsigned long memory, swap; + struct mem_cgroup *mi; /* * Provide statistics on the state of the memory subsystem as @@ -1682,6 +1684,17 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) memcg_events(memcg, memcg_vm_event_stat[i])); } + /* Hierarchical information */ + memory = swap = PAGE_COUNTER_MAX; + for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) { + memory = min(memory, READ_ONCE(mi->memory.max)); + swap = min(swap, READ_ONCE(mi->swap.max)); + } + seq_buf_printf(s, "hierarchical_memory_limit %llu\n", + (u64)memory * PAGE_SIZE); + seq_buf_printf(s, "hierarchical_swap_limit %llu\n", + (u64)swap * PAGE_SIZE); + /* The above should easily fit into one page */ WARN_ON_ONCE(seq_buf_has_overflowed(s)); }
