On 29/10/15 16:32, Benoit Girard wrote: > We've explored several different ways of measuring this. Several of > these are in the tree. Generally what I have found the most useful is to > measure how we're servicing the content' main thread. This measurement > is great because its measures how responsive Firefox is not only for > scrolling/animations but nearly all use cases like typing latency. > > There's EventTracer.h which is our best general responsiveness > measurement at the moment. However it only traces the event loop up to > each 20ms so it's a laggy indicator.
Thanks. However, I'm not really looking for a detector, only a flag that will let me prune false positives. The Performance Stats API already detects [a subset of] lag, and the Addon Watcher informs the user when this lag is attributed to an add-on. Experience shows, however, that it regularly informs the user of invisible lag. In particular, Jetpack causes a CPOW when we're focusing Firefox, even if this has no impact on the user, AdBlock slows down some parts of loading, even if it generally makes loading faster on the whole, etc. While the event loop is not serviced as well as usual, from the point of view of the user, these are false positives. Hence my quest for a way to determine whether the main thread is currently in a jank-critical section (user-interaction or animation). Note that there are secondary applications to this, e.g. bug 1178972. Cheers, David -- David Rajchenbach-Teller, PhD Performance Team, Mozilla
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