what is io_uring?

content/posts/2024-09-32--what-is-io-uring.dj

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+# What is io_uring?
+
+An attempt at concise explanation of what io_uring is.
+
+`io_uring` is a new Linux kernel interface for making system calls.
+Traditionally, syscalls are submitted to the kernel *individually* and
+*synchronously*: a syscall CPU instruction transfers control from the
+application to the kernel; control returns to the application only when the
+syscall is completed. In contrast, `io_uring` is a *batched* and *asynchronous*
+interface. The application submits several syscalls by writing their codes &
+arguments to a lock-free shared-memory ring buffer. The kernel reads the
+syscalls from this shared memory and executes them at its own pace. To
+communicate results back to the application, the kernel writes the results to a
+second lock-free shared-memory ring buffer, where they become available to the
+application asynchronously.
+
+You might want to use `io_uring` if:
+
+- you need extra performance unlocked by amortizing userspace/kernelspace
+  context switching across entire batches of syscalls, 
+- you want a unified asynchronous interface to the entire system.
+
+You might want to avoid `io_uring` if:
+
+- you need to write portable software,
+- you want to use only old, proven features,
+- and in particular you want to use features with a good security track record.