Frame buffer access performance

Daniel Vetter daniel at
Fri Aug 5 08:15:57 UTC 2016

On Fri, Aug 05, 2016 at 04:35:25AM +0200, Enrico Weigelt, metux IT consult wrote:
> Hi folks,
> when putting pixels into an DRM framebuffer, should I do that in
> bursts/blocks instead of byte-per-byte ? (eg. explicitly using
> aligned 32bit ops).

There's a driver cap DRM_CAP_DUMB_PREFER_SHADOW for this. If set, render
into a shadow buffer and copy over in bursts, otherwise you can assume
that the memory is fully cpu cached and fast with random access. Note that
this is just for dumb buffers, which are explicitly not meant as the
fastest memory, but the most convenient (i.e. untiled).
Daniel Vetter
Software Engineer, Intel Corporation

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