waitfd: make punting the waitfd read configurable

emper/Emper.hpp

@@ -161,6 +161,14 @@ const bool IO_NOTIFICATION =
 #endif
 		;
 
+const bool IO_PUNT_WAITFD_READ =
+#ifdef EMPER_IO_PUNT_WAITFD_READ
+		true
+#else
+		false
+#endif
+		;
+
 const bool IO_STEALING =
 #ifdef EMPER_IO_STEALING
 		true

emper/sleep_strategy/WaitfdSleepStrategy.cpp

@@ -61,7 +61,9 @@ void WaitfdSleepStrategy::sleep() {
 	auto customLogic = [this, &io] {
 		// waitfd non-blocking reads will always return -EAGAIN and waitfd is not pollable
 		// therefore we can skip that and immediately issue the read in an async manner.
-		prepareSleepRead(io, waitfd, IOSQE_ASYNC);
+		uint8_t sqe_flags = 0;
+		if constexpr (emper::IO_PUNT_WAITFD_READ) sqe_flags |= IOSQE_ASYNC;
+		prepareSleepRead(io, waitfd, sqe_flags);
 		LOGD("prepared waitfd read");
 		return true;
 	};

meson.build

@@ -194,6 +194,8 @@ io_bool_options = [
 	{'option': 'notification',
 	 'dependencies': {'worker_sleep_strategy': 'waitfd'}},
 	{'option': 'synchronous'},
+	{'option': 'punt_waitfd_read',
+	 'dependencies': {'worker_sleep_strategy': 'waitfd'}},
 ]
 
 io_raw_options = [

meson_options.txt

@@ -73,6 +73,12 @@ option(
   choices: ['none', 'accounting', 'waitFree', 'bestEffort'],
   value: 'none',
 )
+option(
+  'io_punt_waitfd_read',
+  type: 'boolean',
+  description: 'Punt the sleep watfd read to the io_wq',
+  value: false,
+)
 option(
   'wakeup_semaphore_implementation',
   type: 'combo',