[Mesa-dev] [Bug 93686] Performance improvement ?=:=?UTF-8?Q? Please consider hardware ɢᴘᴜ rendering in llvmpipe

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93686

--- Comment #13 from Alex Deucher <alexdeucher at gmail.com> ---
(In reply to ytrezq from comment #10)
> (In reply to Jan Vesely from comment #9)
> > If GPU<->CPU synchronization is the only problem then the idea should work
> > for iGPUs with coherent access to main memory (HSA complaint?). Then again
> > those GPUs probably won't need CPU help any time soon.
> 
> Intel or ᴀᴍᴅ ᴀᴘᴜs can’t (theoretically) do memory sharing between ᴄᴘᴜ ᴀɴᴅ
> ɢᴘᴜ.
> Intel or ᴀᴍᴅ ᴀᴘᴜs use ᴘᴄɪe even if they are on the same die of the ᴄᴘᴜ. The
> ʙɪᴏꜱ  or the ᴜᴇꜰɪ firmware allocate a fixed portion of ʀᴀᴍ that appear as
> part of “hardware reserved memory” to the ᴏꜱ.
> There’s no Unified memory, data has to use the internal ᴘᴄɪe bus. It’s the
> same as if the card was an external one with it’s own memory (though it can
> directly address ᴄᴘᴜ ram modules).
> 

I can't speak for intel, but on AMD APUs, while the GPU appears as a device on
the PCIE bus, it actually has a much faster internal connection to the memory
controller.

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