linux: introduce io_uring support (#3952)

Add io_uring support for several asynchronous file operations:

- read, write
- fsync, fdatasync
- stat, fstat, lstat

io_uring is used when the kernel is new enough, otherwise libuv simply
falls back to the thread pool.

Performance looks great; an 8x increase in throughput has been observed.

This work was sponsored by ISC, the Internet Systems Consortium.

Fixes: https://github.com/libuv/libuv/issues/1947

1 files changed, 19 insertions, 0 deletions

diff --git a/src/unix/internal.h b/src/unix/internal.h
index d439ae6d..08d2d1ce 100644
--- a/src/unix/internal.h
+++ b/src/unix/internal.h
@@ -329,6 +329,24 @@ int uv__random_getentropy(void* buf, size_t buflen);
 int uv__random_readpath(const char* path, void* buf, size_t buflen);
 int uv__random_sysctl(void* buf, size_t buflen);
 
+/* io_uring */
+#ifdef __linux__
+int uv__iou_fs_fsync_or_fdatasync(uv_loop_t* loop,
+                                  uv_fs_t* req,
+                                  uint32_t fsync_flags);
+int uv__iou_fs_read_or_write(uv_loop_t* loop,
+                             uv_fs_t* req,
+                             int is_read);
+int uv__iou_fs_statx(uv_loop_t* loop,
+                     uv_fs_t* req,
+                     int is_fstat,
+                     int is_lstat);
+#else
+#define uv__iou_fs_fsync_or_fdatasync(loop, req, fsync_flags) 0
+#define uv__iou_fs_read_or_write(loop, req, is_read) 0
+#define uv__iou_fs_statx(loop, req, is_fstat, is_lstat) 0
+#endif
+
 #if defined(__APPLE__)
 int uv___stream_fd(const uv_stream_t* handle);
 #define uv__stream_fd(handle) (uv___stream_fd((const uv_stream_t*) (handle)))
@@ -405,6 +423,7 @@ int uv__statx(int dirfd,
               int flags,
               unsigned int mask,
               struct uv__statx* statxbuf);
+void uv__statx_to_stat(const struct uv__statx* statxbuf, uv_stat_t* buf);
 ssize_t uv__getrandom(void* buf, size_t buflen, unsigned flags);
 #endif