std.event.Loop: use EPOLLONESHOT to save 1 syscall
when a thread pool worker accepts a coroutine to resume
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eb326e1553
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@ -132,6 +132,7 @@ pub const Loop = struct {
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pub const EventFd = struct {
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base: ResumeNode,
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epoll_op: u32,
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eventfd: i32,
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};
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};
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@ -204,6 +205,7 @@ pub const Loop = struct {
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.handle = undefined,
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},
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.eventfd = try std.os.linuxEventFd(1, posix.EFD_CLOEXEC | posix.EFD_NONBLOCK),
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.epoll_op = posix.EPOLL_CTL_ADD,
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},
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.next = undefined,
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};
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@ -265,15 +267,20 @@ pub const Loop = struct {
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errdefer {
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_ = @atomicRmw(usize, &self.pending_event_count, AtomicRmwOp.Sub, 1, AtomicOrder.SeqCst);
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}
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try self.addFdNoCounter(fd, resume_node);
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try self.modFd(
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fd,
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posix.EPOLL_CTL_ADD,
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std.os.linux.EPOLLIN | std.os.linux.EPOLLOUT | std.os.linux.EPOLLET,
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resume_node,
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);
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}
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fn addFdNoCounter(self: *Loop, fd: i32, resume_node: *ResumeNode) !void {
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pub fn modFd(self: *Loop, fd: i32, op: u32, events: u32, resume_node: *ResumeNode) !void {
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var ev = std.os.linux.epoll_event{
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.events = std.os.linux.EPOLLIN | std.os.linux.EPOLLOUT | std.os.linux.EPOLLET,
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.events = events,
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.data = std.os.linux.epoll_data{ .ptr = @ptrToInt(resume_node) },
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};
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try std.os.linuxEpollCtl(self.os_data.epollfd, std.os.linux.EPOLL_CTL_ADD, fd, &ev);
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try std.os.linuxEpollCtl(self.os_data.epollfd, op, fd, &ev);
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}
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pub fn removeFd(self: *Loop, fd: i32) void {
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@ -331,7 +338,8 @@ pub const Loop = struct {
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const eventfd_node = &resume_stack_node.data;
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eventfd_node.base.handle = handle;
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// the pending count is already accounted for
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self.addFdNoCounter(eventfd_node.eventfd, &eventfd_node.base) catch |_| {
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const epoll_events = posix.EPOLLONESHOT | std.os.linux.EPOLLIN | std.os.linux.EPOLLOUT | std.os.linux.EPOLLET;
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self.modFd(eventfd_node.eventfd, eventfd_node.epoll_op, epoll_events, &eventfd_node.base) catch |_| {
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// fine, we didn't need it anyway
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_ = @atomicRmw(u8, &self.dispatch_lock, AtomicRmwOp.Xchg, 0, AtomicOrder.SeqCst);
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self.os_data.available_eventfd_resume_nodes.push(resume_stack_node);
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@ -371,7 +379,7 @@ pub const Loop = struct {
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ResumeNode.Id.Stop => return,
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ResumeNode.Id.EventFd => {
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const event_fd_node = @fieldParentPtr(ResumeNode.EventFd, "base", resume_node);
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self.removeFdNoCounter(event_fd_node.eventfd);
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event_fd_node.epoll_op = posix.EPOLL_CTL_MOD;
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const stack_node = @fieldParentPtr(std.atomic.Stack(ResumeNode.EventFd).Node, "data", event_fd_node);
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self.os_data.available_eventfd_resume_nodes.push(stack_node);
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},
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@ -902,7 +910,7 @@ test "std.event.Lock" {
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defer cancel handle;
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loop.run();
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assert(mem.eql(i32, shared_test_data, [1]i32{3 * 10} ** 10));
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assert(mem.eql(i32, shared_test_data, [1]i32{3 * @intCast(i32, shared_test_data.len)} ** shared_test_data.len));
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}
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async fn testLock(loop: *Loop, lock: *Lock) void {
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@ -945,7 +953,7 @@ async fn lockRunner(lock: *Lock) void {
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suspend; // resumed by onNextTick
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var i: usize = 0;
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while (i < 10) : (i += 1) {
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while (i < shared_test_data.len) : (i += 1) {
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const handle = await (async lock.acquire() catch @panic("out of memory"));
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defer handle.release();
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