On 2/9/24 09:48, Jan Kratochvil (Azul) wrote:
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. 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..39f2a4a06 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, memsw;
+ 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 = memsw = PAGE_COUNTER_MAX;
+ for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) {
+ memory = min(memory, READ_ONCE(mi->memory.max));
+ memsw = min(memsw, READ_ONCE(mi->memsw.max));
+ }
+ seq_buf_printf(s, "hierarchical_memory_limit %llu\n",
+ (u64)memory * PAGE_SIZE);
+ seq_buf_printf(s, "hierarchical_memsw_limit %llu\n",
+ (u64)memsw * PAGE_SIZE);
+
/* The above should easily fit into one page */
WARN_ON_ONCE(seq_buf_has_overflowed(s));
}
I don't think we use mi->memsw in cgroup v2, only memory and swap should
be used.
Cheers,
Longman
