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



Even if the true value of the flag isn't returned via
getContextAttributes, the fact is that selecting the low-power mode
may cause a different GPU to be used. Further, the OpenGL drivers for
the integrated GPUs on Mac OS are fairly far away from passing the
WebGL conformance suite. Therefore, adding this flag to the WebGL
specification -- making it a supported feature, which is different
than using an unsupported tool like gfxCardStatus -- has significant
ramifications for WebGL conformance and applications. Even if the true
value of the flag weren't exposed, I would still say that the entire
suite would need to be run twice, once with {
preferLowPowerToHighPerformance: false } and once with {
preferLowPowerToHighPerformance: true }.

-Ken


On Thu, Sep 27, 2012 at 2:10 PM, Florian Bösch <pyalot@gmail.com> wrote:
> From earlier discussion about the discoverability of performance capability
> (see the threads on performance profiles) I thought the consensus
> (grudingly) was not to do this because of UA issues. I see no problem in
> offering the flag but not reflecting its value.
>
> On Thu, Sep 27, 2012 at 11:01 PM, Kenneth Russell <kbr@google.com> wrote:
>>
>> One other issue needing consideration. Let's assume that the
>> "preferLowPowerToHighPerformance" flag is added to the
>> WebGLContextAttributes dictionary, and that
>> WebGLRenderingContext.getContextAttributes() returns the correct value
>> for the flag. (In other words, if the flag is set to true during
>> getContext, and the machine has two GPUs, and the implementation
>> supports low-power mode, then getContextAttributes() will return true
>> for the flag as well; otherwise, false.)
>>
>> On dual-GPU Mac OS machines, at least, it will then be possible to get
>> WebGL to run on either the integrated or discrete GPU, and detect
>> which one is being used in JavaScript.
>>
>> In order to keep implementations honest, it will be necessary to
>> change the WebGL conformance suite to run all of the tests twice, once
>> on the integrated GPU and once on the discrete GPU. 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?

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