LGTM3 (after two LGTM1s from Alex and Yoav).
The finch flag is just a followup on Domenic's question. It seems the
issue is that the documented flag doesn't actually correspond to the
on-off switch for this feature so please update the finch flag
documentation to reflect the correct switch. Just in case this will need
emergency surgery.
There is a discussion to be had about TAG reviews for minor WebGPU
features. By the book this should probably have had one, but I'm not
sure anyone would have benefited from such a request so it's probably
the book that needs updating. Also see Alex' comment below.
/Daniel
On 2024-08-28 18:00, Alex Russell wrote:
Hey folks,
LGTM1 with nits. First, it would be good for y'all to FYI this to the
TAG, even if you don't block on review. I agree it's small and would
wave it through. I know Daniel has questions about the Finch flag
name, so would be good to have those sorted before this goes out too.
Thanks,
Alex
On Wednesday, August 28, 2024 at 5:02:13 AM UTC-7 Corentin Wallez wrote:
On Wed, Aug 28, 2024 at 12:36 PM Yoav Weiss (@Shopify)
<yoavwe...@chromium.org> wrote:
LGTM1
On Fri, Aug 23, 2024 at 2:46 PM 'François Beaufort' via
blink-dev <blink-dev@chromium.org> wrote:
Adding +Corentin Wallez <mailto:cwal...@google.com> to the
thread
On Fri, Aug 23, 2024 at 2:29 PM François Beaufort
<fbeauf...@google.com> wrote:
On Fri, Aug 23, 2024 at 7:01 AM Domenic Denicola
<dome...@chromium.org> wrote:
On Thu, Aug 22, 2024 at 9:13 PM 'François
Beaufort' via blink-dev <blink-dev@chromium.org>
wrote:
Contact emails
fbeauf...@google.com <mailto:fbeauf...@google.com>
Explainer
The “dual-source-blending” GPU feature adds
additional blend factors and the WGSL
@blend_src attribute to allow a fragment
shader to blend two color outputs into a
single output buffer.
https://github.com/gpuweb/gpuweb/pull/4621
<https://github.com/gpuweb/gpuweb/pull/4621>
Specification
https://gpuweb.github.io/gpuweb/#dom-gpufeaturename-dual-source-blending
<https://gpuweb.github.io/gpuweb/#dom-gpufeaturename-dual-source-blending>
Summary
Functionality added to the WebGPU spec after
its first shipment in a browser.
Adds the optional GPU feature
“dual-source-blending” that enables combining
two fragment shader outputs into a single
framebuffer. This technique is particularly
useful for applications that require complex
blending operations, such as those based on
Porter-Duff blend modes. By reducing the need
for frequent pipeline state object changes,
dual source blending can enhance performance
and flexibility.
Blink component
Blink>WebGPU
<https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EWebGPU>
TAG review
None
TAG review status
Not applicable
I can't figure out which exception
<https://www.chromium.org/blink/guidelines/api-owners/process-exceptions/>
this would fall under. Can you help explain why
TAG review is not applicable here?
Back in October 2023, Corentin Wallez, the WebGPU Tech
Lead, met with the Blink API owners to address the
process for releasing WebGPU features following their
inclusion in Chromium. It was mutually agreed that
requesting TAG reviews for minor features would be
unnecessary. This policy applied to all features added
at the time. See
https://groups.google.com/a/chromium.org/g/blink-dev/search?q=%22tag%20review%22%20subject%3Awebgpu
<https://groups.google.com/a/chromium.org/g/blink-dev/search?q=%22tag%20review%22%20subject%3Awebgpu>
I may misremember, but I thought we discussed adding a
"levels" designation to WebGPU additions that would enable us
to create such bypasses for vendor signals and TAG reviews.
Did that actually happen? If so, did we make any progress on that?
In any case, I agree this is a small addition in which I
wouldn't expect the TAG to have meaningful feedback over the
one already provided by the domain experts at the WebGPU group.
We discussed that some larger additions to WebGPU would still
request a TAG review, one of which would be the addition of a
compatibility mode
<https://github.com/gpuweb/gpuweb/blob/main/proposals/compatibility-mode.md> or
feature level mechanism for WebGPU (whichever the WebGPU group
gets to consensus on). We are still making progress on that one,
and don't have other large features being developed yet (only
smaller, GPU-specific additions for now). Other features that
could warrant TAG review would be bindless / ray tracing (though
it's mostly GPU specific), multithreading support, and maybe
interoperation with other Web APIs like canvas
<https://github.com/fserb/canvas2D/blob/master/spec/webgpu.md>
(and canvas shaders
<https://github.com/fserb/canvas2D/blob/master/spec/shaders.md>),
or WebNN <https://github.com/webmachinelearning/webnn/issues/688>.
Risks
Interoperability and Compatibility
This feature has not yet been implemented in
any browser. It has been approved by the GPU
for the Web Community Group, with
representatives from Chrome, Firefox, and
Safari. See minutes at
https://github.com/gpuweb/gpuweb/wiki/GPU-Web-2024-05-29#add-optional-feature-dual_source_blending-4621
<https://github.com/gpuweb/gpuweb/wiki/GPU-Web-2024-05-29#add-optional-feature-dual_source_blending-4621>
Gecko: No signal (Mozilla members have
approved
https://github.com/gpuweb/gpuweb/pull/4621
<https://github.com/gpuweb/gpuweb/pull/4621>
and requested during weekly standardization
meetings that we postpone filing standard
positions until we reach Candidate
Recommendation (CR) status in Q4.)
WebKit: Positive
(https://github.com/WebKit/standards-positions/issues/294#issuecomment-1877411933
<https://github.com/WebKit/standards-positions/issues/294#issuecomment-1877411933>)
Web developers: Positive
(https://github.com/gpuweb/gpuweb/issues/4283
<https://github.com/gpuweb/gpuweb/issues/4283>)
Other signals:
WebView application risks
Does this intent deprecate or change behavior
of existing APIs, such that it has potentially
high risk for Android WebView-based applications?
None
Debuggability
None
Will this feature be supported on all
six Blink platforms (Windows, Mac,
Linux, ChromeOS, Android, and Android
WebView)?
No
All platforms will eventually have support.
Will immediately be available on Android,
Android WebView, ChromeOS, Mac, and Windows,
since those platforms already support WebGPU.
Linux is planned to have WebGPU support in the
future, so this feature will become available
when WebGPU does.
Is this feature fully tested by
web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?
Yes. See
https://github.com/gpuweb/cts/issues/3810
<https://github.com/gpuweb/cts/issues/3810>
WebGPU/WGSL have a conformance test suite
(https://github.com/gpuweb/cts
<https://github.com/gpuweb/cts>) that is
regularly pulled into Chromium and part of the
testing of Dawn/Tint in Chromium.
But, it is not tested by web platform tests
themselves, right?
https://github.com/web-platform-tests/wpt/tree/master/webgpu
<https://github.com/web-platform-tests/wpt/tree/master/webgpu>
seems to not contain any tests for this feature.
(This does not block shipping, but rather is just
a request to improve the accuracy of your Chrome
Platform Status entry.)
As you can see in
https://groups.google.com/a/chromium.org/g/blink-dev/search?q=cts%20web-platform-tests%20subject%3Awebgpu
<https://groups.google.com/a/chromium.org/g/blink-dev/search?q=cts%20web-platform-tests%20subject%3Awebgpu>,
we’ve always replied “Yes” to this question. The
WebGPU/WGSL conformance test suite
(https://github.com/gpuweb/cts) is not used only by
Chromium. Other engines, like WebKit and Gecko, also
rely on this test suite to ensure their implementation
aligns with the WebGPU specification.
This test suite can be exported to WPT and we use that
export for a subset of tests in Chromium for reftests:
https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/web_tests/wpt_internal/webgpu/
<https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/web_tests/wpt_internal/webgpu/>The
rest of the tests are executed with a different
harness in Chromium for better speed and test result
granularity.
Flag name on chrome://flags
None
Finch feature name
WebGPU.Enabled:UnsafeFeatures
This Finch feature name is a bit scary. Does it
actually allow unshipping only this new feature?
It sounds rather general.
It does allow disabling specific GPU features such as
FeatureName::DualSourceBlending, but also
FeatureName::Subgroups, etc.
Seehttps://source.chromium.org/chromium/chromium/src/+/main:gpu/config/gpu_finch_features.cc;l=275;drc=168a59b6bada5b30a6f2390c22a6177216b17e4d
<https://source.chromium.org/chromium/chromium/src/+/main:gpu/config/gpu_finch_features.cc;l=275;drc=168a59b6bada5b30a6f2390c22a6177216b17e4d>.
If it really matters, we could rename the Finch
feature name to WebGPU.Enabled:BlocklistFeatures to
better reflect the meaning.
Requires code in //chrome?
False
Tracking bug
https://issues.chromium.org/issues/341973423
<https://issues.chromium.org/issues/341973423>
Estimated milestones
DevTrial on desktop
129
DevTrial on Android
129
Anticipated spec changes
Open questions about a feature may be a source
of future web compat or interop issues. Please
list open issues (e.g. links to known github
issues in the project for the feature
specification) whose resolution may introduce
web compat/interop risk (e.g., changing to
naming or structure of the API in a
non-backward-compatible way).
None
Link to entry on the Chrome Platform
Status
https://chromestatus.com/feature/5167711051841536
<https://chromestatus.com/feature/5167711051841536>
This intent message was generated by Chrome
Platform Status <https://chromestatus.com/>.
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