On Thu, Apr 30, 2020 at 6:39 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote: > > On Fri, May 1, 2020 at 2:27 AM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > > > Lowering memory.max can trigger an oom-kill if the reclaim does not > > succeed. However if oom-killer does not find a process for killing, it > > dumps a lot of warnings. > > > > I have been confused by this behavior for several months and I think > it will confuse more memcg users. > We should keep the memcg oom behavior consistent with system oom - no > oom kill if no process. > > What about bellow change ? > Seems fine to me. If others are ok with this, please do send a signed-off patch. > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index e28098e13f1c..25fbc37a747f 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6086,6 +6086,9 @@ static ssize_t memory_max_write(struct > kernfs_open_file *of, > continue; > } > > + if (!cgroup_is_populated(memcg->css.cgroup)) > + break; > + > memcg_memory_event(memcg, MEMCG_OOM); > if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0)) > break; > > > Deleting a memcg does not reclaim memory from it and the memory can > > linger till there is a memory pressure. One normal way to proactively > > reclaim such memory is to set memory.max to 0 just before deleting the > > memcg. However if some of the memcg's memory is pinned by others, this > > operation can trigger an oom-kill without any process and thus can log a > > lot un-needed warnings. So, ignore all such warnings from memory.max. > > > > Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> > > --- > > include/linux/oom.h | 3 +++ > > mm/memcontrol.c | 9 +++++---- > > mm/oom_kill.c | 2 +- > > 3 files changed, 9 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/oom.h b/include/linux/oom.h > > index c696c265f019..6345dc55df64 100644 > > --- a/include/linux/oom.h > > +++ b/include/linux/oom.h > > @@ -52,6 +52,9 @@ struct oom_control { > > > > /* Used to print the constraint info. */ > > enum oom_constraint constraint; > > + > > + /* Do not warn even if there is no process to be killed. */ > > + bool no_warn; > > }; > > > > extern struct mutex oom_lock; > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 317dbbaac603..a1f00d9b9bb0 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -1571,7 +1571,7 @@ unsigned long mem_cgroup_size(struct mem_cgroup *memcg) > > } > > > > static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, > > - int order) > > + int order, bool no_warn) > > { > > struct oom_control oc = { > > .zonelist = NULL, > > @@ -1579,6 +1579,7 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, > > .memcg = memcg, > > .gfp_mask = gfp_mask, > > .order = order, > > + .no_warn = no_warn, > > }; > > bool ret; > > > > @@ -1821,7 +1822,7 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int > > mem_cgroup_oom_notify(memcg); > > > > mem_cgroup_unmark_under_oom(memcg); > > - if (mem_cgroup_out_of_memory(memcg, mask, order)) > > + if (mem_cgroup_out_of_memory(memcg, mask, order, false)) > > ret = OOM_SUCCESS; > > else > > ret = OOM_FAILED; > > @@ -1880,7 +1881,7 @@ bool mem_cgroup_oom_synchronize(bool handle) > > mem_cgroup_unmark_under_oom(memcg); > > finish_wait(&memcg_oom_waitq, &owait.wait); > > mem_cgroup_out_of_memory(memcg, current->memcg_oom_gfp_mask, > > - current->memcg_oom_order); > > + current->memcg_oom_order, false); > > } else { > > schedule(); > > mem_cgroup_unmark_under_oom(memcg); > > @@ -6106,7 +6107,7 @@ static ssize_t memory_max_write(struct kernfs_open_file *of, > > } > > > > memcg_memory_event(memcg, MEMCG_OOM); > > - if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0)) > > + if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0, true)) > > break; > > } > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index 463b3d74a64a..5ace39f6fe1e 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -1098,7 +1098,7 @@ bool out_of_memory(struct oom_control *oc) > > > > select_bad_process(oc); > > /* Found nothing?!?! */ > > - if (!oc->chosen) { > > + if (!oc->chosen && !oc->no_warn) { > > dump_header(oc, NULL); > > pr_warn("Out of memory and no killable processes...\n"); > > /* > > -- > > 2.26.2.526.g744177e7f7-goog > > > > > > > -- > Thanks > Yafang