Hi,
On 09.02.2017 17:03, Marek Olšák wrote:
On Thu, Feb 9, 2017 at 1:52 PM, Ian Romanick <i...@freedesktop.org> wrote:
...
No, it absolutely is not fine to merge. We have never allowed such a
thing, and I'll be damned if I'll allow this project to start. Things
that land that are known to be broken never actually get fixed. Then we
have to waste time fielding bug reports and Phoronix threads because
users turn on the performance features and everything breaks. It's just
a terrible idea.
It does pass piglit, but only when it's disabled.
We have to ask the question of how long it will take to reach the
level of perfection that some people here demand. 1 year? 2? 4 years
even? Are we willing to wait that long? Is there a sufficient minimum
requirement on merging this project that's possible to reach within 2
weeks? Instead of saying "absolutely not" and "terrible idea", why not
just say "yes if X gets done"?
<disclaimer: I'm not a Mesa committer so my opinion doesn't count for much>
My personal feeling is that minimal merging criteria should be:
* no known segfaults
* no functional piglit failures (or if there are, they're known,
somewhat investigated and commonly agreed to be OK for merging)
After the functional issues are fixed, performance issues are fine as
long as it still clearly helps (>=10%?) some games.
In general, performance numbers for features that have functional
issues, shouldn't be trusted. If e.g. crashes are due to missing
synchronization, does adding the required synchronization also lose the
measured performance increase?
If you only expect absolutism and perfectionism, you'll be very
disappointed with this project. Doing a threaded GL dispatch is hard.
NVIDIA had had performance issues with it for a very long time.
Those are fine. Have they had also crashes or rendering issues?
Is realistic approach just automatically disabling threading when
program uses problematic GL feature/version? (Can it be disabled if it's
already in use?)
> AMD doesn't even have a solution that can be enabled by default.
>
I'm not heavily invested in this project (yet), so it won't bother me
much if this doesn't get merged before mid-2017. If people wanna
contribute, they can send me pull requests. (please do it early &
often, don't wait until you have something that's good enough)
I've been contemplating doing threaded gallium dispatch for a while
now. It should be very easy if we copy some sync prevention tricks
from radeonsi, and we might be able to enable it by default for all GL
apps (core & compat) from day 1. That can be our short-term goal for
gallium, while threaded GL can be our long-term goal and only limited
to whitelisted apps for quite a while.
- Eero
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