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Carl Lerche
8546ff826d
* runtime: cleanup and add config options This patch finishes the cleanup as part of the transition to Tokio 0.2. A number of changes were made to take advantage of having all Tokio types in a single crate. Also, fixes using Tokio types from `spawn_blocking`. * Many threads, one resource driver Previously, in the threaded scheduler, a resource driver (mio::Poll / timer combo) was created per thread. This was more or less fine, except it required balancing across the available drivers. When using a resource driver from **outside** of the thread pool, balancing is tricky. The change was original done to avoid having a dedicated driver thread. Now, instead of creating many resource drivers, a single resource driver is used. Each scheduler thread will attempt to "lock" the resource driver before parking on it. If the resource driver is already locked, the thread uses a condition variable to park. Contention should remain low as, under load, the scheduler avoids using the drivers. * Add configuration options to enable I/O / time New configuration options are added to `runtime::Builder` to allow enabling I/O and time drivers on a runtime instance basis. This is useful when wanting to create lightweight runtime instances to execute compute only tasks. * Bug fixes The condition variable parker is updated to the same algorithm used in `std`. This is motivated by some potential deadlock cases discovered by `loom`. The basic scheduler is fixed to fairly schedule tasks. `push_front` was accidentally used instead of `push_back`. I/O, time, and spawning now work from within `spawn_blocking` closures. * Misc cleanup The threaded scheduler is no longer generic over `P :Park`. Instead, it is hard coded to a specific parker. Tests, including loom tests, are updated to use `Runtime` directly. This provides greater coverage. The `blocking` module is moved back into `runtime` as all usage is within `runtime` itself.