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Mon, 24 Aug 2026 00:02:32 -0700 (PDT) Date: Mon, 24 Aug 2026 09:02:30 +0200 From: Maxime Ripard To: Eric Chanudet Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Tejun Heo , Johannes Weiner , Michal =?utf-8?Q?Koutn=C3=BD?= , Jonathan Corbet , Shuah Khan , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Shuah Khan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Albert Esteve Subject: Re: [PATCH 03/11] cgroup: add memory_cma_accounting mount option Message-ID: <20260824-poised-meaty-shellfish-9a09d2@houat> References: <20260821-cma-memcg-regions-v1-0-d21b165b8440@redhat.com> <20260821-cma-memcg-regions-v1-3-d21b165b8440@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha384; protocol="application/pgp-signature"; boundary="l2avhy4pfliwz3eh" Content-Disposition: inline In-Reply-To: <20260821-cma-memcg-regions-v1-3-d21b165b8440@redhat.com> X-Rspamd-Queue-Id: 1719E40009 X-Rspam-User: X-Stat-Signature: drghf5dkcnfniq98ycxokgbpez9qnhix X-Rspamd-Server: rspam06 X-HE-Tag: 1787554958-401727 X-HE-Meta: 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 dUxPqpcm 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --l2avhy4pfliwz3eh Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 03/11] cgroup: add memory_cma_accounting mount option MIME-Version: 1.0 On Fri, Aug 21, 2026 at 02:56:55PM -0400, Eric Chanudet wrote: > Add a cgroup v2 mount option that will be used later in this series to > enable CMA memory accounting under memcg. >=20 > The option is made opt-in as it will charge allocations to the cgroup's > overall memory usage, which changes existing expectations. >=20 > Signed-off-by: Eric Chanudet > --- > Documentation/admin-guide/cgroup-v2.rst | 20 ++++++++++++++++++++ > include/linux/cgroup-defs.h | 5 +++++ > kernel/cgroup/cgroup.c | 15 ++++++++++++++- > 3 files changed, 39 insertions(+), 1 deletion(-) >=20 > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admi= n-guide/cgroup-v2.rst > index aed195a71cbf..3dfc13f31a0c 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -246,6 +246,26 @@ cgroup v2 currently supports the following mount opt= ions. > will not be tracked by the memory controller (even if cgroup > v2 is remounted later on). > =20 > + memory_cma_accounting > + Count CMA memory usage towards the cgroup's overall memory usage= for > + the memory controller, and expose per-CMA-area usage counters. T= his > + behavior is opt-in, so as to not cause regression on existing se= tups. > + > + A few caveats to keep in mind: > + > + * CMA areas are reserved at boot time, memory is only charged to= a > + cgroup when a CMA allocation is performed on its behalf. > + * CMA pages allocated while this option is not enabled will not = be > + tracked by the memory controller, even if cgroup v2 is remount= ed > + later on with this option. Charges happen at allocation. And what would happen if it's the other way around, ie mounted with this option enabled, then remounted with the option disabled? Maxime --l2avhy4pfliwz3eh Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJUEABMJAB0WIQTkHFbLp4ejekA/qfgnX84Zoj2+dgUCaovshgAKCRAnX84Zoj2+ dmgFAYD2QpXyIkC2UzudfuMMWSQyhPMvADvZ8Rf/HrEEqUh/MjtRgmrUG5NqgkMI UAktDh4BgIRrcGChUBI+vsNkyPAnIa8ElouZIe+7PjdeK6u1QPgT/QlxiYNC2N8b AaFU79ONPw== =PSxk -----END PGP SIGNATURE----- --l2avhy4pfliwz3eh--