[webkit-dev] Request for Position: Compute Pressure API

[Ryosuke Niwa]

On Wed, May 5, 2021 at 11:37 AM Olivier Yiptong via webkit-dev <
webkit-dev at lists.webkit.org> wrote:

>
> We propose a new API that conveys the utilization of CPU resources on the
> user's device. This API targets applications that can trade off CPU
> resources for an improved user experience. For example, many applications
> can render video effects with varying degrees of sophistication. These
> applications aim to provide the best user experience, while avoiding
> driving the user's device in a high CPU utilization regime.
>
> High CPU utilization is undesirable because it strongly degrades the user
> experience. Many smartphones, tablets and laptops become uncomfortably hot
> to the touch. The fans in laptops and desktops become so loud that they
> disrupt conversations or the users’ ability to focus. In many cases, a
> device under high CPU utilization appears to be unresponsive, as the
> operating system may fail to schedule the threads advancing the task that
> the user is waiting for.
>
> Thanks!
>
>
>    - Specification Title: Compute Pressure API
>    - Specification URL: https://oyiptong.github.io/compute-pressure/
>    - Explainger:
>    https://github.com/oyiptong/compute-pressure/blob/main/README.md
>    - ChromeStatus.com entry:
>    https://chromestatus.com/features/5597608644968448
>    - TAG design review request:
>    https://github.com/w3ctag/design-reviews/issues/621
>    - Mozilla Request for Position:
>    https://github.com/mozilla/standards-positions/issues/521
>
> We do not support this proposal for the reasons including but not limited
to:

   1. CPU utilization isn't something which can be easily computed or
   reasoned on asymmetric multi-core CPUs, not to mention the dynamic
   adjustment of CPU frequency further complicates the matter.
   2. Whether the system itself is under a heavy CPU load or not should not
   have any bearing on how much CPU time a website is entitled to use because
   the background CPU utilization may spontaneously change, and the reason of
   a high or a low CPU utilization may depend on what the website is doing;
   e.g. a daemon which wakes up in a response to a network request or some
   file access.
   3. The proposal as it currently stands seems to allow a side channel
   communication between different top-level origins (i.e. bypasses storage
   partitioning). A possible attack may involve busy looping or doing some
   heavy computation in one origin and then observing that CPU utilization
   goes up in another. We've reported an attack of a similar nature in
   https://bugs.chromium.org/p/chromium/issues/detail?id=1126324.

- R. Niwa
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