Am 27.03.2013 01:43, schrieb Jerome Glisse:
On Tue, Mar 26, 2013 at 6:45 PM, Dave Airlie <airl...@gmail.com> wrote:
correctly). But Marek is quite right that this only counts for state
objects
and makes no sense for set_* and draw_* calls (and I'm currently thinking
how to avoid that and can't come up with a proper solution). Anyway it's
definitely not an urgent problem for radeonsi.
It will be a problem once we actually start caring about performance
and, most importantly, the CPU overhead of the driver.
I still think that writing into the command buffers directly (e.g.
without
wrapper functions) is a bad idea, cause that lead to mixing driver logic
and
I'm convinced the exact opposite is a bad idea, because it adds
another layer all commands must go through. A layer which brings no
advantage. Think about apps which issue 1k-10k draw calls per frame.
It's obvious that every byte moved around counts and the key to high
framerate is to do (almost) nothing in the driver. It looks like the
idea here is to make the driver as slow as possible.
packet building in r600g. For example just try to figure out how the
relocation in NOPs work by reading the source (please keep in mind that
one
of the primary goals why AMD is supporting this driver is to give a good
example code for customers who want to implement that stuff on their own
systems).
I'm shocked. Sacrificing performance in the name of making the code
nicer for some customers? Seriously? I thought the plan was to make
the best graphics driver ever.
Well, maybe I'm repeating myself: Performance is not a priority, it's only
nice to have!
Sorry to say so, but if we sacrifice a bit of performance for more code
readability than that is perfectly ok with me (Don't understand me wrong I
would really prefer to replace the closed source driver today than tomorrow,
it's unfortunately just not what I'm paid for).
On the other hand, we are talking about perfectly optimizeable inline
functions and/or macros. All I'm saying is that we should structurize the
code a bit more.
Its okay to take steps in the right direction, but if you start taking
steps that away
from performance in lieu of code readability then please be prepared
to deal with
objections.
The thing is in a lot of cases, code readability is in the eye of the
beholder, I'm sure
Jerome though r600g was perfectly readable when he wrote it, but a lot
of us didn't
and spent a lot of time trying to remove the CPU overheads, not least
the amount of
time Marek spent. The thing is performance is measureable, code
readability isn't.
Dave.
Maybe once again you forgot why i did things the way i did them, i
explained myself to you back then, i designed r600g for a new kernel
api which was violently different from the cs one, my hope was that
the other kernel api would be better, it was not and i never pushed
more on that front. So r600g design was definitely not adapted to the
cs ioctl and not thinked for it. History often explain a lot of things
and people seems to forget about them.
That being said, i too find ironic the code readability argument, if
one understand the cs ioctl then the r600g code as it's nowadays make
sense, but the radeonsi code is closer to what r600g use to be. So
assuming same ioctl i would say that radeonsi should move towards what
r600g is nowadays.
Anyway just wanted to set history straight.
Well I think you hit the point here quite well, may I ask what your
kernel interface would have been looked like?
Christian.
Cheers,
Jerome
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