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That section describes the "polling". You are right that with normal IO, there doesn't need to be polling, since the completion will be signaled by interrupt. H
by Matthias247 7y ago
That section describes the "polling". You are right that with normal IO, there doesn't need to be polling, since the completion will be signaled by interrupt. However as described in the document polling can be faster for some use-cases. And for those there needs to be one thread which performs the polling for completions. That one can be in the Kernel.
- Const-me 7y agoLooked more closely, indeed you’re right. That section discusses an optional mechanism how the kernel gets notified about new IO requests submit by the application. It’s not for IO completion polling. For that use case, having a kernel thread per uring makes perfect sense.