Hey Francois,
This sounds promising. My one concern is what effect(s) this might have on
our performance benchmarking work. +Camillo Bruni <cbr...@google.com> for
his thoughts. We should at the very least make sure
speedometer/motionmark/etc numbers are not negatively impacted by this
change.
Cheers,
Johnny
On Fri, Feb 7, 2025 at 10:03 AM Francois Pierre Doray <fdo...@chromium.org>
wrote:
> Hi,
>
> We tested an intervention on Canary/Dev/Beta that reduces the frame rate
> by half (e.g., from 60fps to 30fps) after 4 consecutive frames without
> pixel changes. The frame rate returns to normal immediately upon pixel
> changes or input events. For example:
>
> let last = performance.now();
> let c = () => {
> window.requestAnimationFrame(c);
> let now = performance.now();
> console.log(now - last);
> last = now;
> }
> c();
>
> The c() function's invocation frequency halves after 4 calls due to the
> lack of pixel updates. Note: As a result, a subsequent frame with pixel
> updates may be delayed by up to 1 frame (but frame rate returns to normal
> immediately after a frame with pixel updates).
>
> This intervention significantly improves LCP, INP and CPU usage on Beta,
> confirming our prior observation that no-op frames often occupy the main
> thread during page load or input handling. To validate these results, we
> need a 1% stable experiment (user behavior differs between pre-stable and
> stable channels). Before proceeding, we'd appreciate feedback on potential
> issues this experiment might cause. We will determine our next steps based
> on input from this discussion.
>
> Thanks,
>
> François
>
> [cc: Chen, Li and Zheng, Hong from Intel who proposed and implemented
> this intervention]
>
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