Hi Mounir, The reason for a longer trial here is that this proposal is somewhat large, and while enabling auto-vectorization can give some performance benefits, to really experiment with this applications may have to rewrite their existing code that uses native SIMD intrinsics to use portable Wasm intrinsics (example: Emscripten SIMD intrinsics header <https://github.com/emscripten-core/emscripten/blob/master/system/include/wasm_simd128.h>), or builtins that map to Wasm operations.
The intent is to build in enough time for new applications to experiment with this in parallel to ongoing standardization effort in the WebAssembly CG. The ballpark estimate I've used here is from previous applications experimenting with SIMD, with some buffer to gather data. That said, I do understand that this is a longer trial than is usual, so would be open to adjusting the timeline based on concerns. Thanks, Deepti On Friday, March 27, 2020 at 1:29:09 PM UTC-7, Mounir Lamouri wrote: > > Hi Deepti, > > This Intent to Experiment looks good, though, I'm wondering why this is > expected to run for 5 releases, which is roughly 6 months. Is there > something specific we are concerned about and that this timeline aims to > solve? > > -- Mounir > > On Fri, 27 Mar 2020 at 07:22, Deepti Gandluri <gdee...@chromium.org> > wrote: > >> Contact emails >> >> gdee...@chromium.org, nattes...@chromium.org, z...@chromium.org >> >> >> Spec >> >> Overview document: >> https://github.com/WebAssembly/simd/blob/master/proposals/simd/SIMD.md >> >> Proposal directory: >> https://github.com/WebAssembly/simd/tree/master/proposals/simd >> >> Tag review: https://github.com/w3ctag/design-reviews/issues/487 >> >> >> Summary >> >> The WebAssembly SIMD proposal defines a portable, performant subset of >> SIMD operations that map to vector instructions that are available across >> most modern hardware platforms. >> >> >> This is purely a WebAssembly performance feature that adds WebAssembly >> operations and does not affect web API behavior, but is still useful for >> developers to be aware of as it can change performance characteristics of >> applications using WebAssembly. >> >> >> Link to “Intent to Prototype” blink-dev discussion: >> >> This links to the Intent to Implement discussion for Simd.js >> <https://groups.google.com/a/chromium.org/forum/#!searchin/blink-dev/Simd.js%7Csort:date/blink-dev/rhPPSQVodq0/zr4HRxXjBgAJ>, >> >> which was the basis for the WebAssembly SIMD. The Spec section above has >> updated links for WebAssembly SIMD, as well as the Tag review. >> >> >> Goals for experimentation >> >> Performance: >> >> The goal for this experiment is to determine the performance benefit of >> having WebAssembly SIMD enabled applications in production code, and >> determine real world performance numbers. We currently have data from >> isolated benchmarks, and demos, but these do not always reflect real world >> usage. >> >> >> API Shape: >> >> The SIMD proposal currently consists of a set of operations that are well >> supported across most modern hardware platforms. The set of instructions >> available on hardware is large and varied, and we are looking for feedback >> on whether this portable subset is sufficient for a cross section of >> applications. >> >> >> Experimental timeline >> >> M84-M89 >> >> >> Any risks when the experiment finishes? >> >> The risk is a drop in performance for sites that were enhancing >> performance using WebAssembly SIMD operations. >> >> >> Ongoing technical constraints >> >> None. >> >> >> Debuggability >> >> WebAssembly SIMD needs debugging support in devtools for 128-bit values, >> as well as baseline compiler support in V8. Both of these efforts are >> ongoing. (Tracking bugs: crbug.com/v8/10347, crbug.com/v8/9909) >> >> >> Will this feature be supported on all five Blink platforms supported by >> Origin Trials (Windows, Mac, Linux, Chrome OS, and Android)? >> >> Yes. >> >> >> Link to entry on the feature dashboard <https://www.chromestatus.com/> >> >> https://www.chromestatus.com/feature/6533147810332672 >> >> -- >> 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/e4010247-bb4c-47a4-9b82-ea8188c3b232%40chromium.org >> >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/e4010247-bb4c-47a4-9b82-ea8188c3b232%40chromium.org?utm_medium=email&utm_source=footer> >> . >> > -- -- v8-dev mailing list v8-dev@googlegroups.com http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/v8-dev/e9f7ebf3-495e-46b7-82bd-a0f963f1625d%40chromium.org.
