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Fri, 19 Dec 2025 07:58:59 -0800 (PST) Received: from localhost ([2a01:e0a:b25:f902::ff]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47d192e88f5sm49165545e9.0.2025.12.19.07.58.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Dec 2025 07:58:59 -0800 (PST) Date: Fri, 19 Dec 2025 16:58:58 +0100 From: Maxime Ripard To: Christian =?utf-8?B?S8O2bmln?= Cc: "T.J. Mercier" , Eric Chanudet , Sumit Semwal , Benjamin Gaignard , Brian Starkey , John Stultz , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, "open list:MEMORY MANAGEMENT" Subject: Re: [PATCH] dma-buf: system_heap: account for system heap allocation in memcg Message-ID: <20251219-cuddly-platinum-cormorant-ae6d0e@houat> References: <20251211193106.755485-2-echanude@redhat.com> <20251215-sepia-husky-of-eternity-ecf0ce@penduick> <07cdcce2-7724-4fe9-8032-258f6161e71d@amd.com> <20251215-garnet-cheetah-of-adventure-ca6fdc@penduick> <20251219-large-daffy-monkey-74665d@houat> <5eda1755-865c-4bb0-a1a0-a4e6dac5388c@amd.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha384; protocol="application/pgp-signature"; boundary="62gvz4x3u7aurz3v" Content-Disposition: inline In-Reply-To: <5eda1755-865c-4bb0-a1a0-a4e6dac5388c@amd.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 86B11C0007 X-Stat-Signature: 91wz14byuh3u6h18w5meu665bxegg49m X-HE-Tag: 1766159943-163012 X-HE-Meta: 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 9wV0lqjO X6HutztiD1W+zVSXa99Cay2UjZLFHI0fTTfw2Ytegux4FTU5YksTIdrdy2BRDZ7N7gxz2kQ8yIr3rKvSR0SmeJTXeQSyeZUjfHN3fONtnW3iuH/enVX1OE3rktzkCezjFgU5o2l+q+LaFVrQ2Pl1PKiNw4zSO03PIB2PYaBrr3yPFNc+ldpfw+BMTKDwki8twUx7HuCJRHQ6BxuuhctM2Mum9BI9ufdwEn/VpLusa72mv/+TmyeUg4X17ofYTqunlrXksR/RXj32fwOq0OxkXF987lo6ajiCLLPQ7xsnSTxjY1pBoOtK2jLfLWg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --62gvz4x3u7aurz3v Content-Type: text/plain; protected-headers=v1; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH] dma-buf: system_heap: account for system heap allocation in memcg MIME-Version: 1.0 On Fri, Dec 19, 2025 at 02:50:50PM +0100, Christian K=F6nig wrote: > On 12/19/25 11:25, Maxime Ripard wrote: > > On Mon, Dec 15, 2025 at 03:53:22PM +0100, Christian K=F6nig wrote: > >> On 12/15/25 14:59, Maxime Ripard wrote: > ... > >>>>> The shared ownership is indeed broken, but it's not more or less br= oken > >>>>> than, say, memfd + udmabuf, and I'm sure plenty of others. > >>>>> > >>>>> So we really improve the common case, but only make the "advanced" > >>>>> slightly more broken than it already is. > >>>>> > >>>>> Would you disagree? > >>>> > >>>> I strongly disagree. As far as I can see there is a huge chance we > >>>> break existing use cases with that. > >>> > >>> Which ones? And what about the ones that are already broken? > >> > >> Well everybody that expects that driver resources are *not* accounted = to memcg. > >=20 > > Which is a thing only because these buffers have never been accounted > > for in the first place. >=20 > Yeah, completely agree. By not accounting it for such a long time we > ended up with people depending on this behavior. >=20 > Not nice, but that's what it is. >=20 > > So I guess the conclusion is that we shouldn't > > even try to do memory accounting, because someone somewhere might not > > expect that one of its application would take too much RAM in the > > system? >=20 > Well we do need some kind of solution to the problem. Either having > some setting where you say "This memcg limit is inclusive/exclusive > device driver allocated memory" or have a completely separate limit > for device driver allocated memory. A device driver memory specific limit sounds like a good idea because it would make it easier to bridge the gap with dmem. Happy holidays, Maxime --62gvz4x3u7aurz3v Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJUEABMJAB0WIQTkHFbLp4ejekA/qfgnX84Zoj2+dgUCaUV2PQAKCRAnX84Zoj2+ doBbAYCwC6GM+nDbVQ+qPSj3EG6TPcebfy5+uYyIL8SOICJl/3ohBlkB/AN0k0qs +sZn+aYBewZWQxkmfc2iSOFLjm35fV4hD2oDDGu74kWLPPrJefPelEf0OooFJoux CX9E84nf8Q== =seo3 -----END PGP SIGNATURE----- --62gvz4x3u7aurz3v--