Messages in this thread Patch in this message | | | Date | Thu, 29 Oct 2020 10:05:23 -0700 | From | Roman Gushchin <> | Subject | Re: [PATCH v2] mm: memcg: link page counters to root if use_hierarchy is false |
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On Thu, Oct 29, 2020 at 04:39:21PM +0100, Michal Koutny wrote: > Hi. > > On Mon, Oct 26, 2020 at 04:13:26PM -0700, Roman Gushchin <guro@fb.com> wrote: > > Please note, that in the non-hierarchical mode all objcgs are always > > reparented to the root memory cgroup, even if the hierarchy has more > > than 1 level. This patch doesn't change it. > > > > The patch also doesn't affect how the hierarchical mode is working, > > which is the only sane and truly supported mode now. > I agree with the patch and you can add > Reviewed-by: Michal Koutný <mkoutny@suse.com> > > However, it effectively switches any users of root.use_hierarchy=0 (if there > are any, watching the counters of root memcg) into root.use_hierarchy=1. > So I'd show them the warning even with a single level of cgroups, i.e. > add this hunk
It's only partially true. The main difference between the hierarchical and non-hierarchical mode on the following simple example
/ | A / \ B C
is whether A's memory limits are applied to B, and this is not gonna change. However you're right, it will change some root cgroup's numbers.
> > @@ -5356,12 +5356,11 @@ > page_counter_init(&memcg->kmem, &root_mem_cgroup->kmem); > page_counter_init(&memcg->tcpmem, &root_mem_cgroup->tcpmem); > /* > - * Deeper hierachy with use_hierarchy == false doesn't make > + * Hierachy with use_hierarchy == false doesn't make > * much sense so let cgroup subsystem know about this > * unfortunate state in our controller. > */ > - if (parent != root_mem_cgroup) > - memory_cgrp_subsys.broken_hierarchy = true; > + memory_cgrp_subsys.broken_hierarchy = true; > } > > /* The following stuff does not apply to the root */ > > What do you think?
I think it's in a good direction of deprecating the non-hierarchical mode. Shakeel did propose it too.
I'd also change the displayed message to something similar to we print for kmem.limit_in_bytes: pr_warn_once("kmem.limit_in_bytes is deprecated and will be removed. " "Please report your usecase to linux-mm@kvack.org if you " "depend on this functionality.\n");
Thanks!
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