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Subject: Re: [RFC PATCH 0/3] staging: remove fbdev drivers
From: Gerd Hoffmann <kraxel@redhat.com>
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Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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Date: Tue, 13 Dec 2016 08:33:24 +0100
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  Hi,

> The acceleration that most of the 2D things provide isn't ever that
> great, and shadowing is a lot more effective if done properly.

That is probably true for anything pci-ish, because those devices are
optimized for memory writes and reads are horribly slow.  So you surely
want avoid device memory reads and shadowing is a effective way to do
this.

On arm hardware the tradeoff may look quite different, the cpus are
relatively slow and I think most arm gpus don't have dedicated device
memory ...

cheers,
  Gerd