On Fri, Oct 27, 2023 at 2:19 AM Domenic Denicola <[email protected]> wrote:
> > > On Thu, Oct 26, 2023 at 7:21 PM François Beaufort <[email protected]> > wrote: > >> >> >> On Thu, Oct 26, 2023 at 11:05 AM Domenic Denicola <[email protected]> >> wrote: >> >>> >>> >>> On Thu, Oct 26, 2023 at 5:21 PM 'François Beaufort' via blink-dev < >>> [email protected]> wrote: >>> >>>> Contact emails >>>> >>>> [email protected], [email protected] >>>> >>>> Explainer >>>> >>>> https://github.com/gpuweb/gpuweb/issues/614 >>>> >>>> Specification >>>> >>>> https://gpuweb.github.io/gpuweb/#timestamp >>>> >>>> Summary >>>> >>>> WebGPU timestamp queries allow WebGPU applications to measure precisely >>>> (down to the nanosecond) how much time their GPU commands take to execute, >>>> especially at the beginning and end of passes. Timestamp queries are >>>> heavily used to gain insights into the performance and behavior of GPU >>>> workloads. >>>> >>>> While the WebGPU specification makes timestamp queries an optional >>>> feature due to timing attack concerns, we believe that timestamp queries >>>> quantization provides a good middle ground by reducing the precision of >>>> timers. To offer even more advanced protection against timing attacks and >>>> fingerprinting, timestamp queries are also coarsened based on site >>>> isolation status: >>>> >>>> - Isolated contexts: timestamp queries are exposed with a resolution of >>>> 100 microseconds. >>>> >>>> - Non-isolated contexts: timestamp queries are not exposed at all. >>>> >>> >>> By "isolated" do you mean "has the cross-origin isolated capability >>> <https://html.spec.whatwg.org/#concept-settings-object-cross-origin-isolated-capability> >>> "? >>> >> >> Yes. >> >> >>> >>> I wasn't able to find any spec or tests for this requirement, which >>> seems like a potential interoperability issue. >>> >> >> The WebGPU spec currently says: "The feature is optional, and a WebGPU >> implementation may limit its exposure only to those scenarios that are >> trusted." >> See >> https://gpuweb.github.io/gpuweb/#security-timing:~:text=The%20feature%20is%20optional%2C%20and%20a%20WebGPU%20implementation%20may%20limit%20its%20exposure%20only%20to%20those%20scenarios%20that%20are%20trusted >> > > I realize that. I was suggesting that, for interoperability purposes, you > should consider specifying the actual condition, instead of leaving it > vague and optional. (E.g. at least in other standards bodies, we have > guidance to avoid optional or implementation-defined features; instead, we > try to work together with other browser engines to come to a common, > interoperable implementation, backed by a test suite.) > > I hope the API Owners can consider this when deciding whether or not to > approve, as I believe that letting these sorts of non-specified and > non-tested features be shipped is harmful for the platform's health. > > I'll add discussion of that to the agenda for this week's WebGPU meeting: can we agree on the availability of timestamp queries (provided there is hardware support) and the quantization depending on contexts. (but to be perfectly honest I think we'll have pushback). Of course the WebGPU standard body tries to avoid implementation-defined features, and instead have deterministic and tested features, but timestamps is one of the ones that might need to be an exception to it. Let's see what consensus the group comes to! > >> >>> >>> >>>> >>>> Blink component >>>> >>>> Blink>WebGPU >>>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EWebGPU> >>>> >>>> TAG review >>>> >>>> WebGPU spec: https://github.com/w3ctag/design-reviews/issues/626 >>>> >>>> TAG review status >>>> >>>> A new TAG review was not requested because timestamp queries were >>>> already part of the original one for the WebGPU spec and was approved. >>>> >>>> Risks >>>> >>>> Interoperability and Compatibility >>>> >>>> Timestamp queries have not yet been implemented in any browser, but >>>> have been approved by the GPU for the Web Community Group, with >>>> representatives from Chrome, Firefox, and Safari. See >>>> https://github.com/gpuweb/gpuweb/wiki/Minutes-2021-09-27#:~:text=consensus%20to%20support%20end/begin%2Dpass%20timestamp%20queries >>>> >>>> Gecko: Positive (https://bugzilla.mozilla.org/show_bug.cgi?id=1827998) >>>> >>>> WebKit: Positive (https://github.com/gpuweb/gpuweb/pull/2190) >>>> >>>> Web developers: Positive. It’s one of the most common requested >>>> features. Many developers already use it today by running chrome with a >>>> special flag. See >>>> https://omar-shehata.medium.com/how-to-use-webgpu-timestamp-query-9bf81fb5344a >>>> Note that it was heavily used to benchmark and optimize Tensorflow.js. >>>> >>>> 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 at the moment, WebGPU currently does not ship on Android WebView. >>>> Parallel work is occurring to launch WebGPU on Android. >>>> >>>> >>>> Debuggability >>>> >>>> No DevTools changes are required. >>>> >>>> Will this feature be supported on all six Blink platforms (Windows, >>>> Mac, Linux, Chrome OS, Android, and Android WebView)? >>>> >>>> No >>>> >>>> All platforms will eventually have support. Will immediately be >>>> available on ChromeOS, Mac, and Windows, since those platforms already >>>> support WebGPU. Linux and Android are 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 >>>> >>>> WebGPU/WGSL have a conformance test suite ( >>>> https://github.com/gpuweb/cts) that is regularly pulled into Chromium >>>> and part of the testing of Dawn/Tint in Chromium. >>>> >>>> Flag name on chrome://flags >>>> >>>> None >>>> >>>> Finch feature name >>>> >>>> None >>>> >>>> Non-finch justification >>>> >>>> None >>>> >>>> Requires code in //chrome? >>>> >>>> False >>>> >>>> Tracking bug >>>> >>>> https://bugs.chromium.org/p/dawn/issues/detail?id=1800 >>>> >>>> Availability expectation >>>> >>>> Feature is available only in Chromium browsers for the near future, on >>>> the order of months. Other browsers intend to ship WebGPU support, but >>>> don't have specified timelines. >>>> >>>> Non-OSS dependencies >>>> >>>> Does the feature depend on any code or APIs outside the Chromium open >>>> source repository and its open-source dependencies to function? >>>> >>>> No >>>> >>>> Estimated milestones >>>> >>>> Shipping on desktop >>>> >>>> 121 >>>> >>>> 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/5136606877188096 >>>> >>>> This intent message was generated by Chrome Platform Status >>>> <https://chromestatus.com/>. >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "blink-dev" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion on the web visit >>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAPpwU5%2BEFoeuehbvaMwzXK3wZ6UxX0U4n7yZJwwJgVOADbBwHA%40mail.gmail.com >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAPpwU5%2BEFoeuehbvaMwzXK3wZ6UxX0U4n7yZJwwJgVOADbBwHA%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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