path: root/go-patches/highres-timer.patch

From 2975b381dc3f559a2eef875582d73cec00ab6b17 Mon Sep 17 00:00:00 2001
From: Alex Brainman <alex.brainman@gmail.com>
Date: Sun, 19 Jul 2020 16:06:48 +1000
Subject: [PATCH] runtime: use CreateWaitableTimerEx to implement usleep

@jstarks suggested that recent versions of Windows provide access to high resolution timers. See

https://github.com/golang/go/issues/8687#issuecomment-656259353

for details.

I tried to run this C program on my Windows 10 computer

```
 #include <stdio.h>
 #include <Windows.h>

 #pragma comment(lib, "Winmm.lib")

// Apparently this is already defined when I use msvc cl.
//#define CREATE_WAITABLE_TIMER_HIGH_RESOLUTION = 0x00000002;

int usleep(HANDLE timer, LONGLONG d) {
	LARGE_INTEGER liDueTime;
	DWORD ret;
	LARGE_INTEGER StartingTime, EndingTime, ElapsedMicroseconds;
	LARGE_INTEGER Frequency;

	QueryPerformanceFrequency(&Frequency);
	QueryPerformanceCounter(&StartingTime);

	liDueTime.QuadPart = d;
	liDueTime.QuadPart = liDueTime.QuadPart * 10;	// us into 100 of ns units
	liDueTime.QuadPart = -liDueTime.QuadPart;	// negative for relative dure time

	if (!SetWaitableTimer(timer, &liDueTime, 0, NULL, NULL, 0)) {
		printf("SetWaitableTimer failed: errno=%d\n", GetLastError());
		return 1;
	}

	ret = WaitForSingleObject(timer, INFINITE);
	if (ret != WAIT_OBJECT_0) {
		printf("WaitForSingleObject failed: ret=%d errno=%d\n", ret, GetLastError());
		return 1;
	}

	QueryPerformanceCounter(&EndingTime);
	ElapsedMicroseconds.QuadPart = EndingTime.QuadPart - StartingTime.QuadPart;
	ElapsedMicroseconds.QuadPart *= 1000000;
	ElapsedMicroseconds.QuadPart /= Frequency.QuadPart;

	printf("delay is %lld us - slept for %lld us\n", d, ElapsedMicroseconds.QuadPart);

	return 0;
}

int testTimer(DWORD createFlag)
{
	HANDLE timer;

	timer = CreateWaitableTimerEx(NULL, NULL, createFlag, TIMER_ALL_ACCESS);
	if (timer == NULL) {
		printf("CreateWaitableTimerEx failed: errno=%d\n", GetLastError());
		return 1;
	}

	usleep(timer, 1000LL);
	usleep(timer, 100LL);
	usleep(timer, 10LL);
	usleep(timer, 1LL);

	CloseHandle(timer);

	return 0;
}

int main()
{
	printf("\n1. CREATE_WAITABLE_TIMER_HIGH_RESOLUTION is off - timeBeginPeriod is off\n");
	testTimer(0);

	printf("\n2. CREATE_WAITABLE_TIMER_HIGH_RESOLUTION is on - timeBeginPeriod is off\n");
	testTimer(CREATE_WAITABLE_TIMER_HIGH_RESOLUTION);

	timeBeginPeriod(1);

	printf("\n3. CREATE_WAITABLE_TIMER_HIGH_RESOLUTION is off - timeBeginPeriod is on\n");
	testTimer(0);

	printf("\n4. CREATE_WAITABLE_TIMER_HIGH_RESOLUTION is on - timeBeginPeriod is on\n");
	testTimer(CREATE_WAITABLE_TIMER_HIGH_RESOLUTION);
}
```

and I see this output

```
1. CREATE_WAITABLE_TIMER_HIGH_RESOLUTION is off - timeBeginPeriod is off
delay is 1000 us - slept for 4045 us
delay is 100 us - slept for 3915 us
delay is 10 us - slept for 3291 us
delay is 1 us - slept for 2234 us

2. CREATE_WAITABLE_TIMER_HIGH_RESOLUTION is on - timeBeginPeriod is off
delay is 1000 us - slept for 1076 us
delay is 100 us - slept for 569 us
delay is 10 us - slept for 585 us
delay is 1 us - slept for 17 us

3. CREATE_WAITABLE_TIMER_HIGH_RESOLUTION is off - timeBeginPeriod is on
delay is 1000 us - slept for 742 us
delay is 100 us - slept for 893 us
delay is 10 us - slept for 414 us
delay is 1 us - slept for 920 us

4. CREATE_WAITABLE_TIMER_HIGH_RESOLUTION is on - timeBeginPeriod is on
delay is 1000 us - slept for 1466 us
delay is 100 us - slept for 559 us
delay is 10 us - slept for 535 us
delay is 1 us - slept for 5 us
```

That shows, that indeed using CREATE_WAITABLE_TIMER_HIGH_RESOLUTION
will provide sleeps as low as about 500 microseconds, while our
current approach provides about 1 millisecond sleep.

New approach also does not require for timeBeginPeriod to be on,
so this change solves long standing problem with go programs draining
laptop battery, because it calls timeBeginPeriod.

This change will only run on systems where
CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag is available. If not
available, the runtime will fallback to original code that uses
timeBeginPeriod.

This is how this change affects benchmark reported in issue #14790

name               old time/op  new time/op  delta
ChanToSyscallPing  1.05ms ± 2%  0.68ms ±11%  -35.43%  (p=0.000 n=10+10)

The benchmark was run with GOMAXPROCS set to 1.

Fixes #8687
Updates #14790

Change-Id: I5b97ba58289c088c17c05292e12e45285c467eae
---

diff --git a/src/runtime/os_windows.go b/src/runtime/os_windows.go
index a62e941..46f4a23 100644
--- a/src/runtime/os_windows.go
+++ b/src/runtime/os_windows.go
@@ -21,6 +21,7 @@
 //go:cgo_import_dynamic runtime._CreateIoCompletionPort CreateIoCompletionPort%4 "kernel32.dll"
 //go:cgo_import_dynamic runtime._CreateThread CreateThread%6 "kernel32.dll"
 //go:cgo_import_dynamic runtime._CreateWaitableTimerA CreateWaitableTimerA%3 "kernel32.dll"
+//go:cgo_import_dynamic runtime._CreateWaitableTimerExW CreateWaitableTimerExW%4 "kernel32.dll"
 //go:cgo_import_dynamic runtime._DuplicateHandle DuplicateHandle%7 "kernel32.dll"
 //go:cgo_import_dynamic runtime._ExitProcess ExitProcess%1 "kernel32.dll"
 //go:cgo_import_dynamic runtime._FreeEnvironmentStringsW FreeEnvironmentStringsW%1 "kernel32.dll"
@@ -68,6 +69,7 @@
 	_CreateIoCompletionPort,
 	_CreateThread,
 	_CreateWaitableTimerA,
+	_CreateWaitableTimerExW,
 	_DuplicateHandle,
 	_ExitProcess,
 	_FreeEnvironmentStringsW,
@@ -151,6 +153,8 @@
 	waitsema   uintptr // semaphore for parking on locks
 	resumesema uintptr // semaphore to indicate suspend/resume
 
+	highResTimer uintptr // high resolution timer handle used in usleep
+
 	// preemptExtLock synchronizes preemptM with entry/exit from
 	// external C code.
 	//
@@ -407,6 +411,12 @@
 // if we're already using the CPU, but if all Ps are idle there's no
 // need to consume extra power to drive the high-res timer.
 func osRelax(relax bool) uint32 {
+	if haveHighResTimer {
+		// Only call timeBeginPeriod/timeEndPeriod, if
+		// high resolution timer is not available.
+		return 0
+	}
+
 	if relax {
 		return uint32(stdcall1(_timeEndPeriod, 1))
 	} else {
@@ -414,6 +424,37 @@
 	}
 }
 
+// haveHighResTimer determines, if CreateWaitableTimerEx
+// CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag is available.
+var haveHighResTimer = false
+
+// createHighResTimer calls CreateWaitableTimerEx with
+// CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag to create high
+// resolution timer. createHighResTimer returns new timer
+// handle or 0, if CreateWaitableTimerEx failed.
+func createHighResTimer() uintptr {
+	const (
+		// As per @jstarks, see
+		// https://github.com/golang/go/issues/8687#issuecomment-656259353
+		_CREATE_WAITABLE_TIMER_HIGH_RESOLUTION = 0x00000002
+		_TIMER_ALL_ACCESS                      = 0x1F0003
+	)
+	return stdcall4(_CreateWaitableTimerExW, 0, 0, _CREATE_WAITABLE_TIMER_HIGH_RESOLUTION, _TIMER_ALL_ACCESS)
+}
+
+func initHighResTimer() {
+	if GOARCH == "arm" {
+		// TODO: Not yet implemented.
+		return
+	}
+	h := createHighResTimer()
+	if h != 0 {
+		haveHighResTimer = true
+		usleep2Addr = unsafe.Pointer(funcPC(usleep2HighRes))
+		stdcall1(_CloseHandle, h)
+	}
+}
+
 func osinit() {
 	asmstdcallAddr = unsafe.Pointer(funcPC(asmstdcall))
 	usleep2Addr = unsafe.Pointer(funcPC(usleep2))
@@ -429,6 +470,7 @@
 
 	stdcall2(_SetConsoleCtrlHandler, funcPC(ctrlhandler), 1)
 
+	initHighResTimer()
 	timeBeginPeriodRetValue = osRelax(false)
 
 	ncpu = getproccount()
@@ -844,9 +886,20 @@
 	var thandle uintptr
 	stdcall7(_DuplicateHandle, currentProcess, currentThread, currentProcess, uintptr(unsafe.Pointer(&thandle)), 0, 0, _DUPLICATE_SAME_ACCESS)
 
+	// Configure usleep timer, if possible.
+	var timer uintptr
+	if haveHighResTimer {
+		timer = createHighResTimer()
+		if timer == 0 {
+			print("runtime: CreateWaitableTimerEx failed; errno=", getlasterror(), "\n")
+			throw("CreateWaitableTimerEx when creating timer failed")
+		}
+	}
+
 	mp := getg().m
 	lock(&mp.threadLock)
 	mp.thread = thandle
+	mp.highResTimer = timer
 	unlock(&mp.threadLock)
 
 	// Query the true stack base from the OS. Currently we're
@@ -884,6 +937,10 @@
 	lock(&mp.threadLock)
 	stdcall1(_CloseHandle, mp.thread)
 	mp.thread = 0
+	if mp.highResTimer != 0 {
+		stdcall1(_CloseHandle, mp.highResTimer)
+		mp.highResTimer = 0
+	}
 	unlock(&mp.threadLock)
 }
 
@@ -979,6 +1036,7 @@
 // in sys_windows_386.s and sys_windows_amd64.s
 func onosstack(fn unsafe.Pointer, arg uint32)
 func usleep2(usec uint32)
+func usleep2HighRes(usec uint32)
 func switchtothread()
 
 var usleep2Addr unsafe.Pointer
diff --git a/src/runtime/sys_windows_386.s b/src/runtime/sys_windows_386.s
index 9e1f409..4ac1527 100644
--- a/src/runtime/sys_windows_386.s
+++ b/src/runtime/sys_windows_386.s
@@ -428,6 +428,42 @@
 	MOVL	BP, SP
 	RET
 
+// Runs on OS stack. duration (in 100ns units) is in BX.
+TEXT runtime·usleep2HighRes(SB),NOSPLIT,$36
+	// Want negative 100ns units.
+	NEGL	BX
+	MOVL	$-1, hi-4(SP)
+	MOVL	BX, lo-8(SP)
+
+	get_tls(CX)
+	MOVL	g(CX), CX
+	MOVL	g_m(CX), CX
+	MOVL	(m_mOS+mOS_highResTimer)(CX), CX
+	MOVL	CX, saved_timer-12(SP)
+
+	MOVL	$0, fResume-16(SP)
+	MOVL	$0, lpArgToCompletionRoutine-20(SP)
+	MOVL	$0, pfnCompletionRoutine-24(SP)
+	MOVL	$0, lPeriod-28(SP)
+	LEAL	lo-8(SP), BX
+	MOVL	BX, lpDueTime-32(SP)
+	MOVL	CX, hTimer-36(SP)
+	MOVL	SP, BP
+	MOVL	runtime·_SetWaitableTimer(SB), AX
+	CALL	AX
+	MOVL	BP, SP
+
+	MOVL	$0, ptime-28(SP)
+	MOVL	$0, alertable-32(SP)
+	MOVL	saved_timer-12(SP), CX
+	MOVL	CX, handle-36(SP)
+	MOVL	SP, BP
+	MOVL	runtime·_NtWaitForSingleObject(SB), AX
+	CALL	AX
+	MOVL	BP, SP
+
+	RET
+
 // Runs on OS stack.
 TEXT runtime·switchtothread(SB),NOSPLIT,$0
 	MOVL	SP, BP
diff --git a/src/runtime/sys_windows_amd64.s b/src/runtime/sys_windows_amd64.s
index 6c8eecd..8475425 100644
--- a/src/runtime/sys_windows_amd64.s
+++ b/src/runtime/sys_windows_amd64.s
@@ -457,6 +457,38 @@
 	MOVQ	40(SP), SP
 	RET
 
+// Runs on OS stack. duration (in 100ns units) is in BX.
+TEXT runtime·usleep2HighRes(SB),NOSPLIT|NOFRAME,$72
+	MOVQ	SP, AX
+	ANDQ	$~15, SP	// alignment as per Windows requirement
+	MOVQ	AX, 64(SP)
+
+	get_tls(CX)
+	MOVQ	g(CX), CX
+	MOVQ	g_m(CX), CX
+	MOVQ	(m_mOS+mOS_highResTimer)(CX), CX	// hTimer
+	MOVQ	CX, 48(SP)				// save hTimer for later
+	// Want negative 100ns units.
+	NEGQ	BX
+	LEAQ	56(SP), DX				// lpDueTime
+	MOVQ	BX, (DX)
+	MOVQ	$0, R8					// lPeriod
+	MOVQ	$0, R9					// pfnCompletionRoutine
+	MOVQ	$0, AX
+	MOVQ	AX, 32(SP)				// lpArgToCompletionRoutine
+	MOVQ	AX, 40(SP)				// fResume
+	MOVQ	runtime·_SetWaitableTimer(SB), AX
+	CALL	AX
+
+	MOVQ	48(SP), CX				// handle
+	MOVQ	$0, DX					// alertable
+	MOVQ	$0, R8					// ptime
+	MOVQ	runtime·_NtWaitForSingleObject(SB), AX
+	CALL	AX
+
+	MOVQ	64(SP), SP
+	RET
+
 // Runs on OS stack.
 TEXT runtime·switchtothread(SB),NOSPLIT|NOFRAME,$0
 	MOVQ	SP, AX
diff --git a/src/runtime/sys_windows_arm.s b/src/runtime/sys_windows_arm.s
index 256b5ff..e6c61a4 100644
--- a/src/runtime/sys_windows_arm.s
+++ b/src/runtime/sys_windows_arm.s
@@ -468,6 +468,24 @@
 	MOVW	R4, R13			// Restore SP
 	MOVM.IA.W (R13), [R4, R15]	// pop {R4, pc}
 
+// Runs on OS stack. Duration (in 100ns units) is in R0.
+// TODO: neeeds to be implemented properly.
+TEXT runtime·usleep2HighRes(SB),NOSPLIT|NOFRAME,$0
+	MOVM.DB.W [R4, R14], (R13)	// push {r4, lr}
+	MOVW	R13, R4			// Save SP
+	SUB	$8, R13			// R13 = R13 - 8
+	BIC	$0x7, R13		// Align SP for ABI
+	RSB	$0, R0, R3		// R3 = -R0
+	MOVW	$0, R1			// R1 = FALSE (alertable)
+	MOVW	$-1, R0			// R0 = handle
+	MOVW	R13, R2			// R2 = pTime
+	MOVW	R3, 0(R2)		// time_lo
+	MOVW	R0, 4(R2)		// time_hi
+	MOVW	runtime·_NtWaitForSingleObject(SB), R3
+	BL	(R3)
+	MOVW	R4, R13			// Restore SP
+	MOVM.IA.W (R13), [R4, R15]	// pop {R4, pc}
+
 // Runs on OS stack.
 TEXT runtime·switchtothread(SB),NOSPLIT|NOFRAME,$0
 	MOVM.DB.W [R4, R14], (R13)  	// push {R4, lr}