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Re: [Public WebGL] option for suggesting "low power" mode at context creation



On Thu, Sep 27, 2012 at 3:52 PM, Dean Jackson <dino@apple.com> wrote:
>
> On 28/09/2012, at 8:29 AM, Chris Marrin <cmarrin@apple.com> wrote:
>
>
> On Sep 27, 2012, at 3:08 PM, Kenneth Russell <kbr@google.com> wrote:
>
>
> Further, there are
> currently many more test failures on Mac OS when running the
> conformance suite on integrated GPUs than on discrete GPUs. This means
> adding a low-power flag now will delay the point at which the next
> snapshot of the WebGL conformance tests could be successfully passed.
> There had been some hope that a new snapshot could be taken soon,
> after triaging the existing test failures on top of tree.
>
> Dean, Chris, any thoughts on this issue?
>
>
> If we are to make it possible for authors to control which GPU is being used
> then we certainly need to have a conformance suite that tests both paths.
> But an implementation can pass the conformance suite immediately by simply
> ignoring the flag and always enabling the GPU that passes.
>
>
> That's true but then it should ship in that configuration. If that
> implementation intends to ship honoring the low-power GPU preference,
> then it should pass the conformance suite while honoring that
> preference. All I'm trying to say here is that more work will be
> needed on Apple's Intel OpenGL driver (and the WebGL conformance
> suite) in order to reasonably add this flag. Given that, are you still
> in favor of adding it?
>
>
> I think it's better to add it to the spec and leave it turned off until the
> conformance tests can pass than to not add it at all. It will be useful to
> implement it and make it possible to turn it on with a developer switch.
> That way we can run the conformance tests and see the breakage so we can
> submit bugs. And that way, the Apple OpenGL group can also run the tests in
> this config and see the failures for themselves.
>
>
> FWIW, we're treating failures on our Integrated GPUs as important as on our
> Discrete GPUs. In other words, we want to pass in every configuration we
> can.

This is good to hear. There are some open Radars against the Intel
drivers on Mac OS that significantly affect the WebGL conformance
suite, so revisiting those would help. There are also some other
failures which haven't been triaged yet.

> I'm in favour of adding the flag (obviously :).
>
> I'm not exactly sure why we'd need to update the test suite. An
> implementation will be able to ignore this flag at any time, so how can we
> test for it? It's up to the implementation to make sure it passes when in
> this mode.

The test suite should be updated so that it runs twice, once passing
"false" for the preferLowPowerToHighPerformance context creation
attribute for all of the contexts it creates, and once passing "true"
for that attribute. This would ensure that implementations paying
attention to the flag would exercise both code paths. Does that make
sense?

-Ken


> Dean
>
>

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