Re: [PATCH] mm/memcg: support control THP behaviour in cgroup

From: Balbir Singh <bsingharora@gmail.com>
To: CGEL <cgel.zte@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>,
	Shakeel Butt <shakeelb@google.com>,
	Yang Shi <shy828301@gmail.com>, Michal Hocko <mhocko@suse.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Matthew Wilcox <willy@infradead.org>,
	Miaohe Lin <linmiaohe@huawei.com>,
	William Kucharski <william.kucharski@oracle.com>,
	Peter Xu <peterx@redhat.com>, Hugh Dickins <hughd@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Muchun Song <songmuchun@bytedance.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux MM <linux-mm@kvack.org>, Cgroups <cgroups@vger.kernel.org>,
	Yang Yang <yang.yang29@zte.com.cn>
Subject: Re: [PATCH] mm/memcg: support control THP behaviour in cgroup
Date: Wed, 18 May 2022 18:14:45 +1000	[thread overview]
Message-ID: <YoSq9W995QPM6tWQ@balbir-desktop> (raw)
In-Reply-To: <627b2df5.1c69fb81.4a22.160f@mx.google.com>

On Wed, May 11, 2022 at 03:31:00AM +0000, CGEL wrote:
> On Tue, May 10, 2022 at 08:11:16PM -0700, Roman Gushchin wrote:
> > On Tue, May 10, 2022 at 07:47:29PM -0700, Shakeel Butt wrote:
> > > On Tue, May 10, 2022 at 7:19 PM CGEL <cgel.zte@gmail.com> wrote:
> > > >
> > > [...]
> > > > > > >
> > > > > > > All controls in cgroup v2 should be hierarchical. This is really
> > > > > > > required for a proper delegation semantic.
> > > > > > >
> > > > > >
> > > > > > Could we align to the semantic of /sys/fs/cgroup/memory.swappiness?
> > > > > > Some distributions like Ubuntu is still using cgroup v1.
> > > > >
> > > > > Other than enable flag, how would you handle the defrag flag
> > > > > hierarchically? It is much more complicated.
> > > >
> > > > Refer to memory.swappiness for cgroup, this new interface better be independent.
> > > 
> > > Let me give my 0.02. I buy the use-case of Admin restricting THPs to
> > > low priority jobs but I don't think memory controller is the right
> > > place to enforce that policy. Michal gave one way (prctl()) to enforce
> > > that policy. Have you explored the BPF way to enforce this policy?
> > 
> > +1 for bpf
> > 
> > I think these THP hints are too implementation-dependent and unstable to become
> > a part of cgroup API.
> >
> 
> Thanks! If no other suggesting we will submit a bpf version of this patch.
>

What is your proposal for BPF? How do you intend to add attach points
(attach_type) for policy? Is it still going to be per cgroup?

Balbir Singh