Motivation: Add an option (through a SelectStrategy return code) to have the Netty event loop thread to do busy-wait on the epoll. The reason for this change is to avoid the context switch cost that comes when the event loop thread is blocked on the epoll_wait() call. On average, the context switch has a penalty of ~13usec. This benefits both: The latency when reading from a socket Scheduling tasks to be executed on the event loop thread. The tradeoff, when enabling this feature, is that the event loop thread will be using 100% cpu, even when inactive. Modification: Added SelectStrategy option to return BUSY_WAIT Epoll loop will do a epoll_wait() with no timeout Use pause instruction to hint to processor that we're in a busy loop Result: When enabled, minimizes impact of context switch in the critical path |
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test/java/io/netty/channel/epoll |