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Mercier" To: tjmercier@google.com, David Airlie , Daniel Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Jonathan Corbet , Greg Kroah-Hartman , "=?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?=" , Todd Kjos , Martijn Coenen , Joel Fernandes , Christian Brauner , Hridya Valsaraju , Suren Baghdasaryan , Sumit Semwal , "=?UTF-8?q?Christian=20K=C3=B6nig?=" , Benjamin Gaignard , Liam Mark , Laura Abbott , Brian Starkey , John Stultz , Tejun Heo , Zefan Li , Johannes Weiner , Shuah Khan Cc: kaleshsingh@google.com, Kenny.Ho@amd.com, mkoutny@suse.com, skhan@linuxfoundation.org, dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hridya Valsaraju This patch adds a proposal for a new GPU cgroup controller for accounting/limiting GPU and GPU-related memory allocations. The proposed controller is based on the DRM cgroup controller[1] and follows the design of the RDMA cgroup controller. The new cgroup controller would: * Allow setting per-cgroup limits on the total size of buffers charged to it. * Allow setting per-device limits on the total size of buffers allocated by device within a cgroup. * Expose a per-device/allocator breakdown of the buffers charged to a cgroup. The prototype in the following patches is only for memory accounting using the GPU cgroup controller and does not implement limit setting. [1]: https://lore.kernel.org/amd-gfx/20210126214626.16260-1-brian.welty@int= el.com/ Signed-off-by: Hridya Valsaraju Signed-off-by: T.J. Mercier --- v3 changes Remove Upstreaming Plan from gpu-cgroup.rst per John Stultz. Use more common dual author commit message format per John Stultz. --- Documentation/gpu/rfc/gpu-cgroup.rst | 183 +++++++++++++++++++++++++++ Documentation/gpu/rfc/index.rst | 4 + 2 files changed, 187 insertions(+) create mode 100644 Documentation/gpu/rfc/gpu-cgroup.rst diff --git a/Documentation/gpu/rfc/gpu-cgroup.rst b/Documentation/gpu/rfc/g= pu-cgroup.rst new file mode 100644 index 000000000000..5b40d5518a5e --- /dev/null +++ b/Documentation/gpu/rfc/gpu-cgroup.rst @@ -0,0 +1,183 @@ +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +GPU cgroup controller +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Goals +=3D=3D=3D=3D=3D +This document intends to outline a plan to create a cgroup v2 controller s= ubsystem +for the per-cgroup accounting of device and system memory allocated by the= GPU +and related subsystems. + +The new cgroup controller would: + +* Allow setting per-cgroup limits on the total size of buffers charged to = it. + +* Allow setting per-device limits on the total size of buffers allocated b= y a + device/allocator within a cgroup. + +* Expose a per-device/allocator breakdown of the buffers charged to a cgro= up. + +Alternatives Considered +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +The following alternatives were considered: + +The memory cgroup controller +____________________________ + +1. As was noted in [1], memory accounting provided by the GPU cgroup +controller is not a good fit for integration into memcg due to the +differences in how accounting is performed. It implements a mechanism +for the allocator attribution of GPU and GPU-related memory by +charging each buffer to the cgroup of the process on behalf of which +the memory was allocated. The buffer stays charged to the cgroup until +it is freed regardless of whether the process retains any references +to it. On the other hand, the memory cgroup controller offers a more +fine-grained charging and uncharging behavior depending on the kind of +page being accounted. + +2. Memcg performs accounting in units of pages. In the DMA-BUF buffer shar= ing model, +a process takes a reference to the entire buffer(hence keeping it alive) e= ven if +it is only accessing parts of it. Therefore, per-page memory tracking for = DMA-BUF +memory accounting would only introduce additional overhead without any ben= efits. + +[1]: https://patchwork.kernel.org/project/dri-devel/cover/20190501140438.9= 506-1-brian.welty@intel.com/#22624705 + +Userspace service to keep track of buffer allocations and releases +__________________________________________________________________ + +1. There is no way for a userspace service to intercept all allocations an= d releases. +2. In case the process gets killed or restarted, we lose all accounting so= far. + +UAPI +=3D=3D=3D=3D +When enabled, the new cgroup controller would create the following files i= n every cgroup. + +:: + + gpu.memory.current (R) + gpu.memory.max (R/W) + +gpu.memory.current is a read-only file and would contain per-device memory= allocations +in a key-value format where key is a string representing the device name +and the value is the size of memory charged to the device in the cgroup in= bytes. + +For example: + +:: + + cat /sys/kernel/fs/cgroup1/gpu.memory.current + dev1 4194304 + dev2 4194304 + +The string key for each device is set by the device driver when the device= registers +with the GPU cgroup controller to participate in resource accounting(see s= ection +'Design and Implementation' for more details). + +gpu.memory.max is a read/write file. It would show the current total +size limits on memory usage for the cgroup and the limits on total memory = usage +for each allocator/device. + +Setting a total limit for a cgroup can be done as follows: + +:: + + echo =E2=80=9Ctotal 41943040=E2=80=9D > /sys/kernel/fs/cgroup1/gpu= .memory.max + +Setting a total limit for a particular device/allocator can be done as fol= lows: + +:: + + echo =E2=80=9Cdev1 4194304=E2=80=9D > /sys/kernel/fs/cgroup1/gpu.= memory.max + +In this example, 'dev1' is the string key set by the device driver during +registration. + +Design and Implementation +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D + +The cgroup controller would closely follow the design of the RDMA cgroup c= ontroller +subsystem where each cgroup maintains a list of resource pools. +Each resource pool contains a struct device and the counter to track curre= nt total, +and the maximum limit set for the device. + +The below code block is a preliminary estimation on how the core kernel da= ta structures +and APIs would look like. + +.. code-block:: c + + /** + * The GPU cgroup controller data structure. + */ + struct gpucg { + struct cgroup_subsys_state css; + + /* list of all resource pools that belong to this cgroup *= / + struct list_head rpools; + }; + + struct gpucg_device { + /* + * list of various resource pools in various cgroups that= the device is + * part of. + */ + struct list_head rpools; + + /* list of all devices registered for GPU cgroup accountin= g */ + struct list_head dev_node; + + /* name to be used as identifier for accounting and limit = setting */ + const char *name; + }; + + struct gpucg_resource_pool { + /* The device whose resource usage is tracked by this reso= urce pool */ + struct gpucg_device *device; + + /* list of all resource pools for the cgroup */ + struct list_head cg_node; + + /* + * list maintained by the gpucg_device to keep track of it= s + * resource pools + */ + struct list_head dev_node; + + /* tracks memory usage of the resource pool */ + struct page_counter total; + }; + + /** + * gpucg_register_device - Registers a device for memory accountin= g using the + * GPU cgroup controller. + * + * @device: The device to register for memory accounting. Must rem= ain valid + * after registration. + * @name: Pointer to a string literal to denote the name of the de= vice. + */ + void gpucg_register_device(struct gpucg_device *gpucg_dev, const c= har *name); + + /** + * gpucg_try_charge - charge memory to the specified gpucg and gpu= cg_device. + * + * @gpucg: The gpu cgroup to charge the memory to. + * @device: The device to charge the memory to. + * @usage: size of memory to charge in bytes. + * + * Return: returns 0 if the charging is successful and otherwise r= eturns an + * error code. + */ + int gpucg_try_charge(struct gpucg *gpucg, struct gpucg_device *dev= ice, u64 usage); + + /** + * gpucg_uncharge - uncharge memory from the specified gpucg and g= pucg_device. + * + * @gpucg: The gpu cgroup to uncharge the memory from. + * @device: The device to charge the memory from. + * @usage: size of memory to uncharge in bytes. + */ + void gpucg_uncharge(struct gpucg *gpucg, struct gpucg_device *devi= ce, u64 usage); + +Future Work +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +Additional GPU resources can be supported by adding new controller files. diff --git a/Documentation/gpu/rfc/index.rst b/Documentation/gpu/rfc/index.= rst index 91e93a705230..0a9bcd94e95d 100644 --- a/Documentation/gpu/rfc/index.rst +++ b/Documentation/gpu/rfc/index.rst @@ -23,3 +23,7 @@ host such documentation: .. toctree:: =20 i915_scheduler.rst + +.. toctree:: + + gpu-cgroup.rst --=20 2.35.1.1021.g381101b075-goog