linux-kernel - Re: [PATCH RFC 00/12] dma: Enable dmem cgroup tracking

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Message-ID: <20250310-eccentric-wonderful-puffin-ddbb26@houat>
Date: Mon, 10 Mar 2025 15:26:52 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Christian König <christian.koenig@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, Robin Murphy <robin.murphy@....com>, 
	Sumit Semwal <sumit.semwal@...aro.org>, Benjamin Gaignard <benjamin.gaignard@...labora.com>, 
	Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>, 
	"T.J. Mercier" <tjmercier@...gle.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Tomasz Figa <tfiga@...omium.org>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, Ben Woodard <woodard@...hat.com>, 
	Hans Verkuil <hverkuil@...all.nl>, Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, iommu@...ts.linux.dev, 
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH RFC 00/12] dma: Enable dmem cgroup tracking

Hi,

On Mon, Mar 10, 2025 at 03:16:53PM +0100, Christian König wrote:
> [Adding Ben since we are currently in the middle of a discussion
> regarding exactly that problem]
>
> Just for my understanding before I deep dive into the code: This uses
> a separate dmem cgroup and does not account against memcg, don't it?

Yes. The main rationale being that it doesn't always make sense to
register against memcg: a lot of devices are going to allocate from
dedicated chunks of memory that are either carved out from the main
memory allocator, or not under Linux supervision at all.

And if there's no way to make it consistent across drivers, it's not the
right tool.

Maxime

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