beaa5a9117
The compilation of wasm UDFs is performed by a call to a foreign function, which cannot be divided with yielding points and, as a result, causes long reactor stalls for big UDFs. We avoid them by submitting the compilation task to a non-seastar std::thread, and retrieving the result using seastar::alien. The thread is created at the start of the program. It executes tasks from a queue in an infinite loop. All seastar shards reference the thread through a std::shared_ptr to a `alien_thread_runner`. Considering that the compilation takes a long time anyway, the alien_thread_runner is implemented with focus on simplicity more than on performance. The tasks are stored in an std::queue, reading and writing to it is synchronized using an std::mutex for reading/ writing to the queue, and an std::condition_variable waiting until the queue has elements. When the destructor of the alien runner is called, an std::nullopt sentinel is pushed to the queue, and after all remaining tasks are finished and the sentinel is read, the thread finishes. Fixes #12904 Closes #13051 * github.com:scylladb/scylladb: wasm: move compilation to an alien thread wasm: convert compilation to a future
6.8 KiB
6.8 KiB