opt: reduce the potential system calls for waking pollers up

Author: panjf2000

internal/netpoll/epoll_default_poller.go

@@ -179,7 +179,7 @@ func (p *Poller) Polling(callback func(fd int, ev uint32) error) error {
 				queue.PutTask(task)
 			}
 			atomic.StoreInt32(&p.netpollWakeSig, 0)
-			if !p.asyncTaskQueue.Empty() || !p.priorAsyncTaskQueue.Empty() {
+			if (!p.asyncTaskQueue.Empty() || !p.priorAsyncTaskQueue.Empty()) && atomic.CompareAndSwapInt32(&p.netpollWakeSig, 0, 1) {
 				for _, err = unix.Write(p.wfd, b); err == unix.EINTR || err == unix.EAGAIN; _, err = unix.Write(p.wfd, b) {
 				}
 			}

internal/netpoll/epoll_optimized_poller.go

@@ -181,7 +181,7 @@ func (p *Poller) Polling() error {
 				queue.PutTask(task)
 			}
 			atomic.StoreInt32(&p.netpollWakeSig, 0)
-			if !p.asyncTaskQueue.Empty() || !p.priorAsyncTaskQueue.Empty() {
+			if (!p.asyncTaskQueue.Empty() || !p.priorAsyncTaskQueue.Empty()) && atomic.CompareAndSwapInt32(&p.netpollWakeSig, 0, 1) {
 				for _, err = unix.Write(p.wpa.FD, b); err == unix.EINTR || err == unix.EAGAIN; _, err = unix.Write(p.wpa.FD, b) {
 				}
 			}

internal/netpoll/kqueue_default_poller.go

@@ -177,7 +177,7 @@ func (p *Poller) Polling(callback func(fd int, filter int16) error) error {
 				queue.PutTask(task)
 			}
 			atomic.StoreInt32(&p.netpollWakeSig, 0)
-			if !p.asyncTaskQueue.Empty() || !p.priorAsyncTaskQueue.Empty() {
+			if (!p.asyncTaskQueue.Empty() || !p.priorAsyncTaskQueue.Empty()) && atomic.CompareAndSwapInt32(&p.netpollWakeSig, 0, 1) {
 				for _, err = unix.Kevent(p.fd, wakeChanges, nil, nil); err == unix.EINTR || err == unix.EAGAIN; _, err = unix.Kevent(p.fd, wakeChanges, nil, nil) {
 				}
 			}

internal/netpoll/kqueue_optimized_poller.go

@@ -178,7 +178,7 @@ func (p *Poller) Polling() error {
 				queue.PutTask(task)
 			}
 			atomic.StoreInt32(&p.netpollWakeSig, 0)
-			if !p.asyncTaskQueue.Empty() || !p.priorAsyncTaskQueue.Empty() {
+			if (!p.asyncTaskQueue.Empty() || !p.priorAsyncTaskQueue.Empty()) && atomic.CompareAndSwapInt32(&p.netpollWakeSig, 0, 1) {
 				for _, err = unix.Kevent(p.fd, wakeChanges, nil, nil); err == unix.EINTR || err == unix.EAGAIN; _, err = unix.Kevent(p.fd, wakeChanges, nil, nil) {
 				}
 			}