On Fri, Aug 5, 2022 at 11:00 AM Dave Tapuska <dtapu...@chromium.org> wrote:
> Stefan, this was just for "non-zero delay" timers? Are there still
> potential issues there?
>
Ah, sorry, I missed that detail. In that case, I think none of my
objections apply.
>
> On Fri, Aug 5, 2022 at 1:19 PM Stefan Zager <sza...@chromium.org> wrote:
>
>> This is a common programming pattern:
>>
>> requestAnimationFrame(() => {
>> setTimeout(() => {
>> // At this point, it's very likely that layout is clean,
>> // because we *just* completed a rendering update.
>> // Queries of layout information are very unlikely to
>> // trigger a forced layout.
>> document.body.offsetTop;
>> });
>> });
>>
>> Aligning timers will make this strategy for avoiding forced layout less
>> effective, because other non-timer tasks may run ahead of the setTimeout
>> and invalidate layout.
>>
>> Also: the rAF(setTimeout()) construct is used extensively in chromium's
>> test corpus, to schedule work ASAP after a rendering update. Many of our
>> tests use a synchronous compositor: rendering updates happen without delay
>> whenever there are no other tasks ready to run. In other tests, we increase
>> the frequency of rendering updates from 60Hz to 200Hz, just because we know
>> there won't be any long-running tasks and we want the tests to run faster.
>>
>> So... I see potential issues here.
>>
>> On Wed, Aug 3, 2022 at 6:50 AM Etienne Pierre-doray <
>> etien...@chromium.org> wrote:
>>
>>> etien...@chromium.org
>>>
>>> ExplainerNone
>>>
>>> Specification
>>> https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html
>>>
>>> Design docs
>>>
>>> https://docs.google.com/document/d/1OjZoHNvn_vz6bhyww68B_KZBi6_s5arT8xMupuNEnDM/edit
>>>
>>> Summary
>>>
>>> Run all timers (with a few exceptions) with a non-zero delay on a
>>> regular 8ms aligned wake up (125 Hz), instead of as soon as their delay has
>>> passed. This affect DOM timers; On foreground pages, run DOM timers with a
>>> non-zero delay on a regular 8ms aligned wake up, instead of as soon as
>>> their delay has passed. On background pages, DOM timers already run on a
>>> regular 1s aligned wake up (1 Hz), or even less frequently after 5 minutes.
>>>
>>>
>>> Blink componentBlink>Scheduling
>>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EScheduling>
>>>
>>> TAG review
>>>
>>> TAG review statusNot applicable
>>>
>>> Risks
>>>
>>>
>>> Interoperability and Compatibility
>>>
>>> This feature changes the behavior of an existing API in a way that is
>>> spec-compliant (the spec says "Optionally, wait a further
>>> implementation-defined length of time", ref.:
>>> https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html#run-steps-after-a-timeout).
>>> Content that relies on precise timing for DOM Timers may stop working
>>> properly in Chromium with this feature. The risk is mitigated by delaying
>>> DOM Timers by at most 8 ms, and by disabling the feature when WebRTC has
>>> active connections in the process. Content that cannot support a 8 ms delay
>>> would probably be better served by alternative APIs described at
>>> https://developer.chrome.com/blog/timer-throttling-in-chrome-88/#workarounds.
>>> Due to the significant battery savings that come with this feature, we
>>> expect that most browsers will decide to implement it after some time.
>>>
>>>
>>> *Gecko*: No signal
>>>
>>> *WebKit*: No signal
>>>
>>> *Web developers*: No signals
>>>
>>> *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?
>>>
>>>
>>>
>>> Goals for experimentation
>>>
>>> Gain insight on potential compatibility issues and evaluate impact on
>>> guardian metrics (page load, latency).
>>>
>>>
>>> Reason this experiment is being extended
>>>
>>>
>>>
>>> Ongoing technical constraints
>>>
>>>
>>>
>>> Debuggability
>>>
>>> This changes the behavior of an existing API. No new debugging support
>>> is added.
>>>
>>>
>>> Will this feature be supported on all six Blink platforms (Windows, Mac,
>>> Linux, Chrome OS, Android, and Android WebView)?Yes
>>>
>>> Is this feature fully tested by web-platform-tests
>>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>
>>> ?No
>>>
>>> DevTrial instructions
>>> https://github.com/eti-p-doray/align-wakeups/blob/main/HOWTO.md
>>>
>>> Flag namealign-wakeups
>>>
>>> Requires code in //chrome?False
>>>
>>> Tracking bughttps://crbug.com/1153139
>>>
>>> Estimated milestones
>>> OriginTrial desktop last 105
>>> OriginTrial desktop first 105
>>> DevTrial on desktop 105
>>> OriginTrial Android last 105
>>> OriginTrial Android first 105
>>> DevTrial on Android 105
>>> OriginTrial webView last 105
>>> OriginTrial webView first 105We plan to do a 1% Stable experiment for
>>> M105 stable.
>>>
>>> Link to entry on the Chrome Platform Status
>>> https://chromestatus.com/feature/5680188671655936
>>>
>>> --
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>>> .
>>>
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