The concept of per-memcg swappiness has never landed well in memcg for cgroup v2. Add a message to users who use it on v1 hierarchy. Decreased swappiness transforms to memory.swap.max=0 whereas increased swappiness transforms into active memory.reclaim operation. Link: https://lore.kernel.org/r/1577252208-32419-1-git-send-email-teawater@xxxxxxxxx/ Signed-off-by: Michal Koutný <mkoutny@xxxxxxxx> --- Documentation/admin-guide/cgroup-v1/memory.rst | 1 + mm/memcontrol-v1.c | 6 ++++-- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst index 286d16fc22ebb..02b8206a35941 100644 --- a/Documentation/admin-guide/cgroup-v1/memory.rst +++ b/Documentation/admin-guide/cgroup-v1/memory.rst @@ -90,6 +90,7 @@ Brief summary of control files. used. memory.swappiness set/show swappiness parameter of vmscan (See sysctl's vm.swappiness) + Per memcg knob does not exist in cgroup v2. memory.move_charge_at_immigrate This knob is deprecated. memory.oom_control set/show oom controls. This knob is deprecated and shouldn't be diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c index 2be6b9112808c..29ca6489b4ff7 100644 --- a/mm/memcontrol-v1.c +++ b/mm/memcontrol-v1.c @@ -1855,9 +1855,11 @@ static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css, if (val > MAX_SWAPPINESS) return -EINVAL; - if (!mem_cgroup_is_root(memcg)) + if (!mem_cgroup_is_root(memcg)) { + pr_info_once("Per memcg swappiness does not exist in cgroup v2. " + "See memory.reclaim or memory.swap.max there\n ") WRITE_ONCE(memcg->swappiness, val); - else + } else WRITE_ONCE(vm_swappiness, val); return 0; -- 2.48.1
