From b1e46c32db520df88e32339a4afad6b593f064c3 Mon Sep 17 00:00:00 2001
From: Azat Khuzhin <azat@libevent.org>
Date: Mon, 13 Jan 2020 00:33:39 +0300
Subject: [PATCH] test: put thread into real time scheduling class on osx for
 better latencies

---
 CMakeLists.txt       |  1 +
 configure.ac         |  1 +
 event-config.h.cmake |  3 +++
 test/regress_main.c  | 43 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 48 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 53d9c3d4..e33d132c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -441,6 +441,7 @@ endif()
 CHECK_INCLUDE_FILE(sys/uio.h EVENT__HAVE_SYS_UIO_H)
 CHECK_INCLUDE_FILES("sys/types.h;ifaddrs.h" EVENT__HAVE_IFADDRS_H)
 CHECK_INCLUDE_FILE(mach/mach_time.h EVENT__HAVE_MACH_MACH_TIME_H)
+CHECK_INCLUDE_FILE(mach/mach.h EVENT__HAVE_MACH_MACH_H)
 CHECK_INCLUDE_FILE(netinet/tcp.h EVENT__HAVE_NETINET_TCP_H)
 CHECK_INCLUDE_FILE(sys/wait.h EVENT__HAVE_SYS_WAIT_H)
 CHECK_INCLUDE_FILE(sys/resource.h EVENT__HAVE_SYS_RESOURCE_H)
diff --git a/configure.ac b/configure.ac
index 7fa285dc..31a6614d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -222,6 +222,7 @@ AC_CHECK_HEADERS([ \
   fcntl.h \
   ifaddrs.h \
   mach/mach_time.h \
+  mach/mach.h \
   netdb.h \
   netinet/in.h \
   netinet/in6.h \
diff --git a/event-config.h.cmake b/event-config.h.cmake
index 216e7f5c..bbcdbab6 100644
--- a/event-config.h.cmake
+++ b/event-config.h.cmake
@@ -178,6 +178,9 @@
 /* Define to 1 if you have the <mach/mach_time.h> header file. */
 #cmakedefine EVENT__HAVE_MACH_MACH_TIME_H 1
 
+/* Define to 1 if you have the <mach/mach.h> header file. */
+#cmakedefine EVENT__HAVE_MACH_MACH_H 1
+
 /* Define to 1 if you have the <memory.h> header file. */
 #cmakedefine EVENT__HAVE_MEMORY_H 1
 
diff --git a/test/regress_main.c b/test/regress_main.c
index 1b6ede7e..1bf3efc2 100644
--- a/test/regress_main.c
+++ b/test/regress_main.c
@@ -186,6 +186,45 @@ ignore_log_cb(int s, const char *msg)
 {
 }
 
+#if defined(__APPLE__)
+
+#ifdef EVENT__HAVE_MACH_MACH_H
+#include <mach/mach.h>
+#endif
+#ifdef EVENT__HAVE_MACH_MACH_TIME_H
+#include <mach/mach_time.h>
+#endif
+#include <pthread.h>
+
+/**
+ * Put into the real time scheduling class for better timers latency.
+ * https://developer.apple.com/library/archive/technotes/tn2169/_index.html#//apple_ref/doc/uid/DTS40013172-CH1-TNTAG6000
+ */
+void move_pthread_to_realtime_scheduling_class(pthread_t pthread)
+{
+	mach_timebase_info_data_t timebase_info;
+	mach_timebase_info(&timebase_info);
+
+	const uint64_t NANOS_PER_MSEC = 1000000ULL;
+	double clock2abs = ((double)timebase_info.denom / (double)timebase_info.numer) * NANOS_PER_MSEC;
+
+	thread_time_constraint_policy_data_t policy;
+	policy.period      = 0;
+	policy.computation = (uint32_t)(5 * clock2abs); // 5 ms of work
+	policy.constraint  = (uint32_t)(10 * clock2abs);
+	policy.preemptible = FALSE;
+
+	int kr = thread_policy_set(pthread_mach_thread_np(pthread_self()),
+		THREAD_TIME_CONSTRAINT_POLICY,
+		(thread_policy_t)&policy,
+		THREAD_TIME_CONSTRAINT_POLICY_COUNT);
+	if (kr != KERN_SUCCESS) {
+		mach_error("thread_policy_set:", kr);
+		exit(1);
+	}
+}
+#endif
+
 void *
 basic_test_setup(const struct testcase_t *testcase)
 {
@@ -199,6 +238,10 @@ basic_test_setup(const struct testcase_t *testcase)
 		evthread_flags |= EVTHREAD_PTHREAD_PRIO_INHERIT;
 #endif
 
+#if defined(__APPLE__)
+	move_pthread_to_realtime_scheduling_class(pthread_self());
+#endif
+
 #ifndef _WIN32
 	if (testcase->flags & TT_ENABLE_IOCP_FLAG)
 		return (void*)TT_SKIP;
-- 
2.40.0