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[doc] requirements: Add section encouraging DMABUF use for iGPUs

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Jonathan Rubenstein 2024-04-08 06:53:11 +03:00
parent ecd3692e1e
commit 65e6ecbe41
1 changed files with 20 additions and 2 deletions
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doc/requirements.rst
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@ -56,8 +56,6 @@ At this time the recommended configuration is as follows:
* AMD or Intel brand GPU for the client application (usually your host system). * AMD or Intel brand GPU for the client application (usually your host system).
* NVIDIA brand GPU for the guest system (virtual machine). * NVIDIA brand GPU for the guest system (virtual machine).
The reason for these recommendations are as follows:
AMD or Intel for the client AMD or Intel for the client
^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -78,3 +76,23 @@ NVIDIA unlike AMD do not seem to suffer from the same stability issues as AMD
GPUs when operating as a passthrough GPU, however due to the closed source GPUs when operating as a passthrough GPU, however due to the closed source
nature of their drivers NVIDIA can not make use of the DMABUF feature in the nature of their drivers NVIDIA can not make use of the DMABUF feature in the
Linux kernel unless you use the open source NVIDIA drivers. Linux kernel unless you use the open source NVIDIA drivers.
.. _igpu_kvmfr_recommended:
iGPUs should use DMABUF
^^^^^^^^^^^^^^^^^^^^^^^
While `DMABUF` with the `KVMFR module <ivshmem_kvmfr>` offers performance
benefits for all users, for the often bandwidth-starved users with an iGPU on
their host it's considered necessary for a decent experience.
When using a normal SHM file, many GPU drivers will copy incoming frames from
shared memory to an intermediary buffer, then upload it from that buffer to the
GPU's framebuffer. The KVMFR module will instead use the GPU's copy engine to
download incoming frames directly from shared memory without using an
intermediary buffer. This is especially helpful to iGPU users as it frees up RAM
bandwidth, which an iGPU already uses extensively.
An added benefit: since the upload is done with the iGPU's copy engine, the CPU
load is reduced as the upload is done by the iGPU module rather than the
processor cores.