ubuntu-x-swat team mailing list archive

[madbiologist <s.j.turner@xxxxxxxxx>]

In the Phoronix forums I found this post by AMD Linux's John Bridgman:

"Note that the KMS performance hits are highly system-specific - eg on
balance my system feels as fast or faster with KMS than with UMS.

I think the limiting factor is CPU power (ie the KMS code uses more CPU
cycles than the UMS code), so it's extra important to make sure that
your power management settings aren't slowing down the CPU when you need
it."

Also, from your XorgLog:

(--) RADEON(0): Chipset: "ATI Mobility Radeon X1600" (ChipID = 0x71c5)
(II) RADEON(0): PCIE card detected
(II) RADEON(0): KMS Color Tiling: disabled

In the same thread on the Phornix forums I found this:

"KMS is slower because color tiling in DDX is disabled by default. You
need to enable it in xorg.conf, see "man radeon". The man page is for
UMS so it lies sometimes."

The relevant section of the radeon manpage is:

Option "ColorTiling" "boolean"

-- 
[radeon driver] (regression) poor video decoding performance
https://bugs.launchpad.net/bugs/578224
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