On Thu, Oct 26, 2023 at 1:21 AM 'François Beaufort' via blink-dev < blink-dev@chromium.org> wrote:
> Contact emails > > fbeauf...@google.com, cwal...@google.com > > 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. > For what it's worth, I suspect that it would be ok to expose the same resolution as `performance.now()`, which is available in non-isolated contexts. Kai's https://github.com/gpuweb/gpuweb/issues/4175 discusses this (aligning the coarsening behavior with the HR-time spec). I do think it'd be fine to ship what you're suggesting and then align the behavior (which would make it more precise) later. Jeffrey -- 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 blink-dev+unsubscr...@chromium.org. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANh-dXnF1vTsEbP9LzxEwqHVbsq0LbLqq3NqVsHgqrDX-Dhs2w%40mail.gmail.com.
