Commen=
t # 15
on bug 75719<=
/a>
from Thomas Hellstr=C3=B6m
(In reply to comment #=
14)
> (In reply to comment #8)
> > So if CPU usage is drastically increased by this commit (or rathe=
r this
> > merge), IMHO that points to a bug somewhere else, but triggered b=
y this
> > merge; possibly in radeon / TTM caching setup or in the x86 PAT m=
emory
> > region tracking code.
> >=20
>=20
> Seems like that is the case... VM_PFNMAP usage instead of VM_MIXEDMAP
> triggers that i now need 'nopat' boot option it is also workaround...=
=20=20
>=20
> So only 'nopat' option work here good with VM_PFNMAP or like before
> VM_MIXEDMAP is good with PAT... VM_PFNMAP with PAT here is really unus=
able
> for gl videos :).
Interesting, although it's not the first time x86 pat/caching has busted
graphics performance-wise, which might appear a bit strange considering
graphics is a major user.
In any case, I'll put together a patch to revert the VM_PFNMAP usage until =
I've
figured out what's really happening (it's only there to boost performance
anyway).
Meanwhile, the fact that this is visible also points to an area of potential
improvement in the radeon driver. Apparently video playback causes a lot of
buffer maps / unmaps. Could the maps somehow be cached in the driver?
Thanks,
Thomas