make cooperative task_work flag configurable

This is needed to measure its impact in the emper-fs-eval.

emper/Emper.hpp

@@ -161,6 +161,14 @@ const bool IO_NOTIFICATION =
 #endif
 		;
 
+const bool IO_URING_COOP_TASKRUN =
+#ifdef EMPER_IO_URING_COOP_TASKRUN
+		true
+#else
+		false
+#endif
+		;
+
 const bool IO_STEAL_ALL_ON_NOTIFICATION =
 #ifdef EMPER_IO_STEAL_ALL_ON_NOTIFICATION
 		true

emper/io/IoContext.cpp

@@ -608,8 +608,10 @@ IoContext::IoContext(Runtime &runtime, size_t uring_entries, unsigned unboundedI
 	 * generated means io-stealing is less efficient since the time a cqe resides in
 	 * a CQ is reduced.
 	 */
-	if (EMPER_LINUX_GE("5.19")) {
-		params.flags |= IORING_SETUP_COOP_TASKRUN | IORING_SETUP_TASKRUN_FLAG;
+	if constexpr (emper::IO_URING_COOP_TASKRUN) {
+		if (EMPER_LINUX_GE("5.19")) {
+			params.flags |= IORING_SETUP_COOP_TASKRUN | IORING_SETUP_TASKRUN_FLAG;
+		}
 	}
 
 	auto ret = io_uring_queue_init_params(uring_entries, &ring, &params);

meson.build

@@ -184,6 +184,7 @@ if option_io
 endif
 
 io_bool_options = [
+	{'option': 'uring_coop_taskrun'},
 	{'option': 'stealing'},
 	{'option': 'lockless_cq'},
 	{'option': 'single_uring',

meson_options.txt

@@ -257,6 +257,12 @@ option(
   value: false,
   description: 'Try non blocking syscalls before submitting the request to io_uring'
 )
+option(
+  'io_uring_coop_taskrun',
+  type: 'boolean',
+  value: true,
+  description: 'Set io_uring TASKRUN flags to use cooperative task_work'
+)
 option(
   'io_worker_uring_entries',
   type: 'integer',