net, runtime: enable runtime-integrated pollster on Linux/ARM.

Results from linux/arm on a Samsung Chromebook (from dfc):
localhost(~/go/src/pkg/net) % ~/go/misc/benchcmp {old,new}.txt
benchmark                           old ns/op    new ns/op    delta
BenchmarkTCP4OneShot                   568840       350526  -38.38%
BenchmarkTCP4OneShot-2                 359054       206708  -42.43%
BenchmarkTCP4OneShotTimeout            637464       363550  -42.97%
BenchmarkTCP4OneShotTimeout-2          374255       216695  -42.10%
BenchmarkTCP4Persistent                184974        64984  -64.87%
BenchmarkTCP4Persistent-2              109902        47195  -57.06%
BenchmarkTCP4PersistentTimeout         210039        64789  -69.15%
BenchmarkTCP4PersistentTimeout-2       124284        43374  -65.10%
BenchmarkTCP6OneShot                   672278       362116  -46.14%
BenchmarkTCP6OneShot-2                 383631       216400  -43.59%
BenchmarkTCP6OneShotTimeout            680740       378306  -44.43%
BenchmarkTCP6OneShotTimeout-2          397524       230152  -42.10%
BenchmarkTCP6Persistent                172346        65292  -62.12%
BenchmarkTCP6Persistent-2              106229        42096  -60.37%
BenchmarkTCP6PersistentTimeout         161149        65138  -59.58%
BenchmarkTCP6PersistentTimeout-2       152276        44548  -70.75%

R=golang-dev, dave, bradfitz, dvyukov, rsc
CC=golang-dev
https://golang.org/cl/7820045

8 files changed, 72 insertions, 200 deletions

diff --git a/src/pkg/net/fd_linux.go b/src/pkg/net/fd_linux.go
deleted file mode 100644
index b83d0348c1..0000000000
--- a/src/pkg/net/fd_linux.go
+++ /dev/null
@@ -1,194 +0,0 @@
-// Copyright 2009 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build arm
-
-// Waiting for FDs via epoll(7).
-
-package net
-
-import (
-	"os"
-	"syscall"
-)
-
-const (
-	readFlags  = syscall.EPOLLIN | syscall.EPOLLRDHUP
-	writeFlags = syscall.EPOLLOUT
-)
-
-type pollster struct {
-	epfd int
-
-	// Events we're already waiting for
-	// Must hold pollServer lock
-	events map[int]uint32
-
-	// An event buffer for EpollWait.
-	// Used without a lock, may only be used by WaitFD.
-	waitEventBuf [10]syscall.EpollEvent
-	waitEvents   []syscall.EpollEvent
-
-	// An event buffer for EpollCtl, to avoid a malloc.
-	// Must hold pollServer lock.
-	ctlEvent syscall.EpollEvent
-}
-
-func newpollster() (p *pollster, err error) {
-	p = new(pollster)
-	if p.epfd, err = syscall.EpollCreate1(syscall.EPOLL_CLOEXEC); err != nil {
-		if err != syscall.ENOSYS {
-			return nil, os.NewSyscallError("epoll_create1", err)
-		}
-		// The arg to epoll_create is a hint to the kernel
-		// about the number of FDs we will care about.
-		// We don't know, and since 2.6.8 the kernel ignores it anyhow.
-		if p.epfd, err = syscall.EpollCreate(16); err != nil {
-			return nil, os.NewSyscallError("epoll_create", err)
-		}
-		syscall.CloseOnExec(p.epfd)
-	}
-	p.events = make(map[int]uint32)
-	return p, nil
-}
-
-// First return value is whether the pollServer should be woken up.
-// This version always returns false.
-func (p *pollster) AddFD(fd int, mode int, repeat bool) (bool, error) {
-	// pollServer is locked.
-
-	var already bool
-	p.ctlEvent.Fd = int32(fd)
-	p.ctlEvent.Events, already = p.events[fd]
-	if !repeat {
-		p.ctlEvent.Events |= syscall.EPOLLONESHOT
-	}
-	if mode == 'r' {
-		p.ctlEvent.Events |= readFlags
-	} else {
-		p.ctlEvent.Events |= writeFlags
-	}
-
-	var op int
-	if already {
-		op = syscall.EPOLL_CTL_MOD
-	} else {
-		op = syscall.EPOLL_CTL_ADD
-	}
-	if err := syscall.EpollCtl(p.epfd, op, fd, &p.ctlEvent); err != nil {
-		return false, os.NewSyscallError("epoll_ctl", err)
-	}
-	p.events[fd] = p.ctlEvent.Events
-	return false, nil
-}
-
-func (p *pollster) StopWaiting(fd int, bits uint) {
-	// pollServer is locked.
-
-	events, already := p.events[fd]
-	if !already {
-		// The fd returned by the kernel may have been
-		// cancelled already; return silently.
-		return
-	}
-
-	// If syscall.EPOLLONESHOT is not set, the wait
-	// is a repeating wait, so don't change it.
-	if events&syscall.EPOLLONESHOT == 0 {
-		return
-	}
-
-	// Disable the given bits.
-	// If we're still waiting for other events, modify the fd
-	// event in the kernel.  Otherwise, delete it.
-	events &= ^uint32(bits)
-	if int32(events)&^syscall.EPOLLONESHOT != 0 {
-		p.ctlEvent.Fd = int32(fd)
-		p.ctlEvent.Events = events
-		if err := syscall.EpollCtl(p.epfd, syscall.EPOLL_CTL_MOD, fd, &p.ctlEvent); err != nil {
-			print("Epoll modify fd=", fd, ": ", err.Error(), "\n")
-		}
-		p.events[fd] = events
-	} else {
-		if err := syscall.EpollCtl(p.epfd, syscall.EPOLL_CTL_DEL, fd, nil); err != nil {
-			print("Epoll delete fd=", fd, ": ", err.Error(), "\n")
-		}
-		delete(p.events, fd)
-	}
-}
-
-// Return value is whether the pollServer should be woken up.
-// This version always returns false.
-func (p *pollster) DelFD(fd int, mode int) bool {
-	// pollServer is locked.
-
-	if mode == 'r' {
-		p.StopWaiting(fd, readFlags)
-	} else {
-		p.StopWaiting(fd, writeFlags)
-	}
-
-	// Discard any queued up events.
-	i := 0
-	for i < len(p.waitEvents) {
-		if fd == int(p.waitEvents[i].Fd) {
-			copy(p.waitEvents[i:], p.waitEvents[i+1:])
-			p.waitEvents = p.waitEvents[:len(p.waitEvents)-1]
-		} else {
-			i++
-		}
-	}
-	return false
-}
-
-func (p *pollster) WaitFD(s *pollServer, nsec int64) (fd int, mode int, err error) {
-	for len(p.waitEvents) == 0 {
-		var msec int = -1
-		if nsec > 0 {
-			msec = int((nsec + 1e6 - 1) / 1e6)
-		}
-
-		s.Unlock()
-		n, err := syscall.EpollWait(p.epfd, p.waitEventBuf[0:], msec)
-		s.Lock()
-
-		if err != nil {
-			if err == syscall.EAGAIN || err == syscall.EINTR {
-				continue
-			}
-			return -1, 0, os.NewSyscallError("epoll_wait", err)
-		}
-		if n == 0 {
-			return -1, 0, nil
-		}
-		p.waitEvents = p.waitEventBuf[0:n]
-	}
-
-	ev := &p.waitEvents[0]
-	p.waitEvents = p.waitEvents[1:]
-
-	fd = int(ev.Fd)
-
-	if ev.Events&writeFlags != 0 {
-		p.StopWaiting(fd, writeFlags)
-		return fd, 'w', nil
-	}
-	if ev.Events&readFlags != 0 {
-		p.StopWaiting(fd, readFlags)
-		return fd, 'r', nil
-	}
-
-	// Other events are error conditions - wake whoever is waiting.
-	events, _ := p.events[fd]
-	if events&writeFlags != 0 {
-		p.StopWaiting(fd, writeFlags)
-		return fd, 'w', nil
-	}
-	p.StopWaiting(fd, readFlags)
-	return fd, 'r', nil
-}
-
-func (p *pollster) Close() error {
-	return os.NewSyscallError("close", syscall.Close(p.epfd))
-}
diff --git a/src/pkg/net/fd_poll_runtime.go b/src/pkg/net/fd_poll_runtime.go
index 999d0215b9..e3b4f7e464 100644
--- a/src/pkg/net/fd_poll_runtime.go
+++ b/src/pkg/net/fd_poll_runtime.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin linux,386 linux,amd64
+// +build darwin linux
 
 package net
 
diff --git a/src/pkg/net/fd_poll_unix.go b/src/pkg/net/fd_poll_unix.go
index cacdba25eb..307e577e99 100644
--- a/src/pkg/net/fd_poll_unix.go
+++ b/src/pkg/net/fd_poll_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd linux,arm netbsd openbsd
+// +build freebsd netbsd openbsd
 
 package net
 
diff --git a/src/pkg/runtime/defs_linux_arm.h b/src/pkg/runtime/defs_linux_arm.h
index 82442b23e0..92160966e1 100644
--- a/src/pkg/runtime/defs_linux_arm.h
+++ b/src/pkg/runtime/defs_linux_arm.h
@@ -2,6 +2,7 @@
 
 // Constants
 enum {
+	EINTR  = 0x4,
 	ENOMEM = 0xc,
 	EAGAIN = 0xb,
 
@@ -65,6 +66,17 @@ enum {
 	ITIMER_VIRTUAL = 0x1,
 	O_RDONLY = 0,
 	O_CLOEXEC = 02000000,
+
+	EPOLLIN		= 0x1,
+	EPOLLOUT	= 0x4,
+	EPOLLERR	= 0x8,
+	EPOLLHUP	= 0x10,
+	EPOLLRDHUP	= 0x2000,
+	EPOLLET		= -0x80000000,
+	EPOLL_CLOEXEC	= 0x80000,
+	EPOLL_CTL_ADD	= 0x1,
+	EPOLL_CTL_DEL	= 0x2,
+	EPOLL_CTL_MOD	= 0x3,
 };
 
 // Types
@@ -146,4 +158,11 @@ struct Sigaction {
 	void *sa_restorer;
 	uint64 sa_mask;
 };
+
+typedef struct EpollEvent EpollEvent;
+struct EpollEvent {
+	uint32	events;
+	uint32	_pad;
+	uint64	data;
+};
 #pragma pack off
diff --git a/src/pkg/runtime/netpoll.goc b/src/pkg/runtime/netpoll.goc
index 152fa174e9..b314c65338 100644
--- a/src/pkg/runtime/netpoll.goc
+++ b/src/pkg/runtime/netpoll.goc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin linux,386 linux,amd64
+// +build darwin linux
 
 package net
 
diff --git a/src/pkg/runtime/netpoll_epoll.c b/src/pkg/runtime/netpoll_epoll.c
index 53916e1d2e..34ed78addb 100644
--- a/src/pkg/runtime/netpoll_epoll.c
+++ b/src/pkg/runtime/netpoll_epoll.c
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build linux,386 linux,amd64
+// +build linux
 
 #include "runtime.h"
 #include "defs_GOOS_GOARCH.h"
diff --git a/src/pkg/runtime/netpoll_stub.c b/src/pkg/runtime/netpoll_stub.c
index a70b2f772f..39d19a4cea 100644
--- a/src/pkg/runtime/netpoll_stub.c
+++ b/src/pkg/runtime/netpoll_stub.c
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd linux,arm netbsd openbsd plan9 windows
+// +build freebsd netbsd openbsd plan9 windows
 
 #include "runtime.h"
 
diff --git a/src/pkg/runtime/sys_linux_arm.s b/src/pkg/runtime/sys_linux_arm.s
index e3994bccaa..7f813482d1 100644
--- a/src/pkg/runtime/sys_linux_arm.s
+++ b/src/pkg/runtime/sys_linux_arm.s
@@ -36,6 +36,11 @@
 #define SYS_ugetrlimit (SYS_BASE + 191)
 #define SYS_sched_getaffinity (SYS_BASE + 242)
 #define SYS_clock_gettime (SYS_BASE + 263)
+#define SYS_epoll_create (SYS_BASE + 250)
+#define SYS_epoll_ctl (SYS_BASE + 251)
+#define SYS_epoll_wait (SYS_BASE + 252)
+#define SYS_epoll_create1 (SYS_BASE + 357)
+#define SYS_fcntl (SYS_BASE + 55)
 
 #define ARM_BASE (SYS_BASE + 0x0f0000)
 
@@ -371,7 +376,6 @@ cascheck:
 	MOVW $0, R0
 	RET
 
-
 TEXT runtime·casp(SB),7,$0
 	B	runtime·cas(SB)
 
@@ -387,3 +391,46 @@ TEXT runtime·sched_getaffinity(SB),7,$0
 	MOVW	$SYS_sched_getaffinity, R7
 	SWI	$0
 	RET
+
+// int32 runtime·epollcreate(int32 size)
+TEXT runtime·epollcreate(SB),7,$0
+	MOVW	0(FP), R0
+	MOVW	$SYS_epoll_create, R7
+	SWI	$0
+	RET
+
+// int32 runtime·epollcreate1(int32 flags)
+TEXT runtime·epollcreate1(SB),7,$0
+	MOVW	0(FP), R0
+	MOVW	$SYS_epoll_create1, R7
+	SWI	$0
+	RET
+
+// int32 runtime·epollctl(int32 epfd, int32 op, int32 fd, EpollEvent *ev)
+TEXT runtime·epollctl(SB),7,$0
+	MOVW	0(FP), R0
+	MOVW	4(FP), R1
+	MOVW	8(FP), R2
+	MOVW	12(FP), R3
+	MOVW	$SYS_epoll_ctl, R7
+	SWI	$0
+	RET
+
+// int32 runtime·epollwait(int32 epfd, EpollEvent *ev, int32 nev, int32 timeout)
+TEXT runtime·epollwait(SB),7,$0
+	MOVW	0(FP), R0
+	MOVW	4(FP), R1
+	MOVW	8(FP), R2
+	MOVW	12(FP), R3
+	MOVW	$SYS_epoll_wait, R7
+	SWI	$0
+	RET
+
+// void runtime·closeonexec(int32 fd)
+TEXT runtime·closeonexec(SB),7,$0
+	MOVW	0(FP), R0	// fd
+	MOVW	$2, R1	// F_SETFD
+	MOVW	$1, R2	// FD_CLOEXEC
+	MOVW	$SYS_fcntl, R7
+	SWI $0
+	RET