[haiku-bugs] Re: [Haiku] #5383: MTRR regression: AGP transfer inconsistencies
- From: "rudolfc" <trac@xxxxxxxxxxxx>
- Date: Thu, 18 Feb 2010 11:38:32 -0000
#5383: MTRR regression: AGP transfer inconsistencies
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Reporter: rudolfc | Owner: bonefish
Type: bug | Status: in-progress
Priority: normal | Milestone: R1
Component: - General | Version: R1/Development
Keywords: | Blockedby: 5353
Platform: All | Blocking:
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Comment(by rudolfc):
The driver's buffer is used for writing by the CPU only. The GPU reads
from this buffer.
Using MTRR-WC has a big-time acceleration performance increase compared to
write-trough or uncached (especially in accelerated 3D, I benchmarked this
once). If MTRR-WC cannot be done for this buffer, then the buffer should
be either write-trough or uncached, but _not_ write-back. the same goes
for 3D buffers in main memory holding graphics instructions or bitmaps
(preventing drawing artifacts).
Write-back cache can only be used if the driver's accelerant can flush the
buffers before marking them as active to the GPU, without a performance
penalty as compared to using MTRR-WC.
It's good to see you are going to work on this, thanks a lot!
Rudolf.
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Ticket URL: <http://dev.haiku-os.org/ticket/5383#comment:7>
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