[Bringing John Lehner from the iTunes team into the discussion] Last I knew, the iTunes team uses fibers. IIRC, the thread they use to call into WebKit/JSC only has one fiber, other parts of the app use multiple fibers on one thread but don’t have JS objects active in those threads / fibers.
John, have things changed for iTunes on Windows such that we can eliminate support for fibers? - Michael > On Dec 5, 2017, at 10:16 AM, Ryosuke Niwa <rn...@webkit.org> wrote: > > Yeah, I don't think there is much need to support fibers. With features like > web workers, supporting fibers doesn't make much sense. > > - R. Niwa > > On Tue, Dec 5, 2017 at 9:44 AM, Yusuke SUZUKI <utatane....@gmail.com > <mailto:utatane....@gmail.com>> wrote: > Hi, Webkittens, > > I would like to make sure OR declare that WebKit does not support Windows > fibers. > While fiber related functions are used in WTF, I believe that it is because > fiber local storage (FLS) can have destructors. And it is not intended to > support fibers explicitly. > > Actually, I believe the current WebKit does not work well with Windows fibers > right now. > For example, our JSC GC is conservative for stack and registers. It means > that GC needs to scan stack and registers to gather conservative roots. But > if your fiber is not executed at that time, JSC GC will miss to scan the > stack and registers of those inactive fibers. As a result, managed objects > will be collected if it is only referenced from the roots in the inactive > fibers. > > And I think we can potentially improve performance of our TLS by using > thread_local implementation in VC++ instead of using FLS. FLS is slow and it > causes some problems[1]. I'm not sure the performance characteristics and > implementation details of thread_local in VC++, but it's worth checking. > > So, I think we should not support Windows fibers. I would like to hear > opinions about it. > > [1]: https://bugs.webkit.org/show_bug.cgi?id=146448 > <https://bugs.webkit.org/show_bug.cgi?id=146448> > > Best regards, > Yusuke Suzuki > > _______________________________________________ > webkit-dev mailing list > webkit-dev@lists.webkit.org <mailto:webkit-dev@lists.webkit.org> > https://lists.webkit.org/mailman/listinfo/webkit-dev > <https://lists.webkit.org/mailman/listinfo/webkit-dev> > > > _______________________________________________ > webkit-dev mailing list > webkit-dev@lists.webkit.org > https://lists.webkit.org/mailman/listinfo/webkit-dev
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