[COMMIT seastar master] reactor: make io_uring the default backend if available

[Commit Bot]

From: Kefu Chai <tcha...@gmail.com>
Committer: Avi Kivity <a...@scylladb.com>
Branch: master

reactor: make io_uring the default backend if available

now that io_uring's performance is on par with that of linux-aio,
and its throughput is always better than linux-aio, let's make
it the default reactor backend. please note, io_uring is disabled
by default on RHEL/RockyLinux 9 at the time of writing.

Signed-off-by: Kefu Chai <tcha...@gmail.com>

---
diff --git a/src/core/reactor_backend.cc b/src/core/reactor_backend.cc
--- a/src/core/reactor_backend.cc
+++ b/src/core/reactor_backend.cc
@@ -2003,15 +2003,15 @@ reactor_backend_selector reactor_backend_selector::default_backend() {

std::vector<reactor_backend_selector> reactor_backend_selector::available() {
std::vector<reactor_backend_selector> ret;
- if (has_enough_aio_nr() && detect_aio_poll()) {
- ret.push_back(reactor_backend_selector("linux-aio"));
- }
- ret.push_back(reactor_backend_selector("epoll"));
#ifdef SEASTAR_HAVE_URING
if (detect_io_uring()) {
ret.push_back(reactor_backend_selector("io_uring"));
}
#endif
+ if (has_enough_aio_nr() && detect_aio_poll()) {
+ ret.push_back(reactor_backend_selector("linux-aio"));
+ }
+ ret.push_back(reactor_backend_selector("epoll"));
return ret;
}