perf: use block syscall enter for epoll_wait

poll_default_linux.go

@@ -97,13 +97,25 @@ func (p *defaultPoll) Wait() (err error) {
 		if n == p.size && p.size < 128*1024 {
 			p.Reset(p.size<<1, caps)
 		}
-		n, err = EpollWait(p.fd, p.events, msec)
+		// msec: 0(raw) => 1ms(sched,raw) => -1(block_syscall)
+		// poller's G will hold P at most 1ms
+		if msec > 0 {
+			n, err = EpollWaitRaw(p.fd, p.events, msec)
+		} else if msec == 0 {
+			n, err = EpollWaitRaw(p.fd, p.events, msec)
+		} else { // < 0
+			n, err = EpollWaitBlock(p.fd, p.events, msec)
+		}
 		if err != nil && err != syscall.EINTR {
 			return err
 		}
 		if n <= 0 {
-			msec = -1
-			runtime.Gosched()
+			if msec > 0 {
+				msec = -1 // no need to sched, because we will use block syscall
+			} else if msec == 0 {
+				msec = 1
+				runtime.Gosched()
+			}
 			continue
 		}
 		msec = 0

sys_epoll.s

@@ -0,0 +1,28 @@
+// Copyright 2023 CloudWeGo Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "textflag.h"
+
+// func epollwaitblock(epfd int32, ev *epollevent, nev, timeout int32) int32
+TEXT ·epollwaitblock(SB),NOSPLIT,$0-28
+	CALL	·entersyscallblock(SB)
+	MOVL	epfd+0(FP), DI
+	MOVQ	ev+8(FP), SI
+	MOVL	nev+16(FP), DX
+	MOVL	timeout+20(FP), R10
+	MOVL	$0xe8, AX // SYS_epoll_wait
+	SYSCALL
+	MOVL	AX, ret+24(FP)
+	CALL	·exitsyscall(SB)
+	RET

sys_epoll_linux.go

@@ -48,15 +48,36 @@ func EpollCtl(epfd int, op int, fd int, event *epollevent) (err error) {
 	return err
 }
 
-// EpollWait implements epoll_wait.
 func EpollWait(epfd int, events []epollevent, msec int) (n int, err error) {
 	var r0 uintptr
 	var _p0 = unsafe.Pointer(&events[0])
-	if msec == 0 {
-		r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_WAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), 0, 0, 0)
-	} else {
-		r0, _, err = syscall.Syscall6(syscall.SYS_EPOLL_WAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	r0, _, err = syscall.Syscall6(syscall.SYS_EPOLL_WAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	if err == syscall.Errno(0) {
+		err = nil
+	}
+	return int(r0), err
+}
+
+func EpollWaitRaw(epfd int, events []epollevent, msec int) (n int, err error) {
+	var r0 uintptr
+	var _p0 = unsafe.Pointer(&events[0])
+	r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_WAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	if err == syscall.Errno(0) {
+		err = nil
 	}
+	return int(r0), err
+}
+
+//go:nosplit
+func EpollWaitBlock(epfd int, events []epollevent, msec int) (n int, err error) {
+	var r0 uintptr
+	var _epfd = uintptr(epfd)
+	var _p0 = uintptr(unsafe.Pointer(&events[0]))
+	var _events_size = uintptr(len(events))
+	var _msec = uintptr(msec)
+	entersyscallblock()
+	r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_WAIT, _epfd, _p0, _events_size, _msec, 0, 0)
+	exitsyscall()
 	if err == syscall.Errno(0) {
 		err = nil
 	}

sys_epoll_linux_arm64.go

@@ -46,15 +46,36 @@ func EpollCtl(epfd int, op int, fd int, event *epollevent) (err error) {
 	return err
 }
 
-// EpollWait implements epoll_wait.
 func EpollWait(epfd int, events []epollevent, msec int) (n int, err error) {
 	var r0 uintptr
 	var _p0 = unsafe.Pointer(&events[0])
-	if msec == 0 {
-		r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), 0, 0, 0)
-	} else {
-		r0, _, err = syscall.Syscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	r0, _, err = syscall.Syscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	if err == syscall.Errno(0) {
+		err = nil
+	}
+	return int(r0), err
+}
+
+func EpollWaitRaw(epfd int, events []epollevent, msec int) (n int, err error) {
+	var r0 uintptr
+	var _p0 = unsafe.Pointer(&events[0])
+	r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	if err == syscall.Errno(0) {
+		err = nil
 	}
+	return int(r0), err
+}
+
+//go:nosplit
+func EpollWaitBlock(epfd int, events []epollevent, msec int) (n int, err error) {
+	var r0 uintptr
+	var _epfd = uintptr(epfd)
+	var _p0 = uintptr(unsafe.Pointer(&events[0]))
+	var _events_size = uintptr(len(events))
+	var _msec = uintptr(msec)
+	entersyscallblock()
+	r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_PWAIT, _epfd, _p0, _events_size, _msec, 0, 0)
+	exitsyscall()
 	if err == syscall.Errno(0) {
 		err = nil
 	}

sys_epoll_linux_loong64.go

@@ -49,15 +49,36 @@ func EpollCtl(epfd int, op int, fd int, event *epollevent) (err error) {
 	return err
 }
 
-// EpollWait implements epoll_wait.
 func EpollWait(epfd int, events []epollevent, msec int) (n int, err error) {
 	var r0 uintptr
 	var _p0 = unsafe.Pointer(&events[0])
-	if msec == 0 {
-		r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), 0, 0, 0)
-	} else {
-		r0, _, err = syscall.Syscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	r0, _, err = syscall.Syscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	if err == syscall.Errno(0) {
+		err = nil
+	}
+	return int(r0), err
+}
+
+func EpollWaitRaw(epfd int, events []epollevent, msec int) (n int, err error) {
+	var r0 uintptr
+	var _p0 = unsafe.Pointer(&events[0])
+	r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(_p0), uintptr(len(events)), uintptr(msec), 0, 0)
+	if err == syscall.Errno(0) {
+		err = nil
 	}
+	return int(r0), err
+}
+
+//go:nosplit
+func EpollWaitBlock(epfd int, events []epollevent, msec int) (n int, err error) {
+	var r0 uintptr
+	var _epfd = uintptr(epfd)
+	var _p0 = uintptr(unsafe.Pointer(&events[0]))
+	var _events_size = uintptr(len(events))
+	var _msec = uintptr(msec)
+	entersyscallblock()
+	r0, _, err = syscall.RawSyscall6(syscall.SYS_EPOLL_PWAIT, _epfd, _p0, _events_size, _msec, 0, 0)
+	exitsyscall()
 	if err == syscall.Errno(0) {
 		err = nil
 	}

sys_exec.go

@@ -24,6 +24,25 @@ import (
 	"unsafe"
 )
 
+//go:noescape
+func epollwaitblock(epfd int32, ev *epollevent, nev, timeout int32) int32
+
+//go:linkname _entersyscallblock runtime.entersyscallblock
+func _entersyscallblock()
+
+//go:linkname _exitsyscall runtime.exitsyscall
+func _exitsyscall()
+
+//go:nosplit
+func entersyscallblock() {
+	_entersyscallblock()
+}
+
+//go:nosplit
+func exitsyscall() {
+	_exitsyscall()
+}
+
 // GetSysFdPairs creates and returns the fds of a pair of sockets.
 func GetSysFdPairs() (r, w int) {
 	fds, _ := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0)