node: remove local_time and use the scheduler's global time instead

src/io_interface.zig

@@ -1215,7 +1215,7 @@ fn now(userdata: ?*anyopaque, clock: Clock) Timestamp {
     // TODO: Return an appropriate time for each clock
     _ = clock;
 
-    return .{ .nanoseconds = node.local_time * 1000 };
+    return .{ .nanoseconds = node.scheduler.current_time * 1000 };
 }
 
 fn clockResolution(userdata: ?*anyopaque, clock: Clock) Clock.ResolutionError!Duration {

src/node.zig

@@ -75,7 +75,6 @@ entry: Scheduler.MainEntryPoint,
 stack_size: usize,
 recoverable: bool,
 faults_enabled: bool,
-local_time: u64,
 file_system: FileSystem,
 real_io: std.Io,
 
@@ -191,7 +190,6 @@ pub fn init(self: *Node, real_io: std.Io, trace: *Trace, prng: *std.Random.Defau
     self.stack_size = options.stack_size;
     self.recoverable = options.recoverable;
     self.faults_enabled = true;
-    self.local_time = 0;
     self.runtime = null;
     try self.file_system.init(self.gpa);
     errdefer self.file_system.deinit(gpa);

src/scheduler.zig

@@ -27,7 +27,6 @@ const ContextSwitch = extern struct {
 
 const STACK_CANARY_SIZE = 256;
 const STACK_CANARY_BYTE = 0xa5;
-const TASK_RUN_COST_US = 50;
 
 pub const TaskID = u64;
 
@@ -305,9 +304,6 @@ fn advanceTimeAndUnblockTasks(self: *Scheduler, new_time: u64) void {
     std.debug.assert(self.current_time < new_time);
     const old_time = self.current_time;
     self.current_time = new_time;
-    for (self.tasks.items) |task| {
-        task.node.local_time = @max(task.node.local_time, new_time);
-    }
     self.trace.timeAdvanced(old_time, new_time);
     for (self.tasks.items) |*task| {
         if (task.state == .blocked) {
@@ -427,7 +423,6 @@ fn taskStart(self: *Scheduler) callconv(.c) noreturn {
     current.wakeup_time = null;
     current.wakeup_tasks = null;
     current.wakeup_futex = null;
-    current.node.local_time += TASK_RUN_COST_US;
     self.traceTaskState(current, if (failed) .failed else .returned, "task completed");
     if (current.parent_id) |parent_id| {
         if (self.findTaskByID(parent_id)) |parent| {
@@ -459,7 +454,6 @@ pub fn sleep(self: *Scheduler, delta_us: u64) !void {
     current.wakeup_time = self.current_time + delta_us;
     current.wakeup_tasks = null;
     current.wakeup_futex = null;
-    current.node.local_time += TASK_RUN_COST_US;
     self.traceTaskState(current, .sleeping, "sleep");
     contextSwitch(&current.regs, &self.regs);
     const resumed = self.findTaskByID(id).?;
@@ -483,7 +477,6 @@ pub fn futexWaitUncancelable(self: *Scheduler, ptr: *const u32, expected: u32) v
     current.wakeup_time = null;
     current.wakeup_tasks = null;
     current.wakeup_futex = ptr;
-    current.node.local_time += TASK_RUN_COST_US;
     self.traceTaskState(current, .waiting_futex, "futex wait");
     contextSwitch(&current.regs, &self.regs);
     const resumed = self.findTaskByID(id).?;
@@ -532,7 +525,6 @@ pub fn wait(self: *Scheduler, ids: []const TaskID) !TaskID {
         task.wakeup_time = null;
         task.wakeup_tasks = ids;
         task.wakeup_futex = null;
-        task.node.local_time += TASK_RUN_COST_US;
         self.traceTaskState(task, .waiting_task, "wait");
         contextSwitch(&task.regs, &self.regs);
         const resumed = self.findTaskByID(id).?;

src/trace.zig

@@ -31,7 +31,7 @@ pub const Trace = struct {
 
     const Pending = struct {
         trace_id: u64,
-        local_time: u64,
+        start_time: u64,
         global_time: u64,
         node_id: u32,
         task_id: TaskID,
@@ -82,12 +82,11 @@ pub const Trace = struct {
         if (self.file == null) return;
 
         const global_time = self.scheduler.current_time;
-        const local_time = node.local_time;
 
         var line_buffer: [256]u8 = undefined;
         const prefix = std.fmt.bufPrint(&line_buffer,
             \\{{"time":{},"global_time":{},"event":"task_spawned","node":{},"task":{}
-        , .{ local_time, global_time, node.id, task_id }) catch return;
+        , .{ global_time, global_time, node.id, task_id }) catch return;
         self.write(prefix);
         if (parent_id) |it| {
             const parent = std.fmt.bufPrint(&line_buffer, ",\"parent\":{}", .{it}) catch return;
@@ -100,13 +99,12 @@ pub const Trace = struct {
         if (self.file == null) return;
 
         const global_time = self.scheduler.current_time;
-        const local_time = node.local_time;
 
         var line_buffer: [256]u8 = undefined;
         const line = std.fmt.bufPrint(&line_buffer,
             \\{{"time":{},"global_time":{},"event":"task_removed","node":{},"task":{}}}
             \\
-        , .{ local_time, global_time, node.id, task_id }) catch return;
+        , .{ global_time, global_time, node.id, task_id }) catch return;
         self.write(line);
     }
 
@@ -114,12 +112,11 @@ pub const Trace = struct {
         if (self.file == null) return;
 
         const global_time = self.scheduler.current_time;
-        const local_time = node.local_time;
 
         var line_buffer: [256]u8 = undefined;
         const prefix = std.fmt.bufPrint(&line_buffer,
             \\{{"time":{},"global_time":{},"event":"state","node":{},"task":{},"state":
-        , .{ local_time, global_time, node.id, task_id }) catch return;
+        , .{ global_time, global_time, node.id, task_id }) catch return;
         self.write(prefix);
         self.writeJsonString(state.toString());
         self.write(",\"reason\":");
@@ -142,7 +139,7 @@ pub const Trace = struct {
         if (self.file == null)
             return .{
                 .trace_id = 0,
-                .local_time = 0,
+                .start_time = 0,
                 .global_time = 0,
                 .task_id = 0,
                 .node_id = 0,
@@ -156,7 +153,6 @@ pub const Trace = struct {
         const task = self.task.?;
 
         const global_time = self.scheduler.current_time;
-        const local_time = node.local_time;
 
         const trace_id = self.next_trace_id;
         self.next_trace_id += 1;
@@ -164,7 +160,7 @@ pub const Trace = struct {
         var line_buffer: [256]u8 = undefined;
         const prefix = std.fmt.bufPrint(&line_buffer,
             \\{{"time":{},"global_time":{},"event":"io_start","id":{},"node":{},"task":{},"op":
-        , .{ local_time, global_time, trace_id, node.id, task }) catch @panic("TODO");
+        , .{ global_time, global_time, trace_id, node.id, task }) catch @panic("TODO");
         self.write(prefix);
         self.writeJsonString(source.fn_name);
         self.write(",\"resource\":");
@@ -173,7 +169,7 @@ pub const Trace = struct {
 
         return .{
             .trace_id = trace_id,
-            .local_time = local_time,
+            .start_time = global_time,
             .global_time = global_time,
             .node_id = node.id,
             .task_id = task,
@@ -194,20 +190,18 @@ pub const Trace = struct {
         if (self.file == null) return;
 
         const global_time = self.scheduler.current_time;
-        const node = self.node orelse return;
-        const local_time = node.local_time;
 
         var line_buffer: [256]u8 = undefined;
         const prefix = std.fmt.bufPrint(&line_buffer,
             \\{{"time":{},"global_time":{},"event":"io_complete","id":{},"node":{},"task":{},"op":
-        , .{ local_time, global_time, pending_trace.trace_id, pending_trace.node_id, pending_trace.task_id }) catch return;
+        , .{ global_time, global_time, pending_trace.trace_id, pending_trace.node_id, pending_trace.task_id }) catch return;
         self.write(prefix);
         self.writeJsonString(pending_trace.op);
         self.write(",\"resource\":");
         self.writeJsonString(if (pending_trace.disk) "disk" else "io");
         const suffix = std.fmt.bufPrint(&line_buffer,
             \\,"start":{},"end":{},"result":
-        , .{ pending_trace.local_time, local_time }) catch return;
+        , .{ pending_trace.start_time, global_time }) catch return;
         self.write(suffix);
         var result_buffer: [96]u8 = undefined;
         self.writeJsonString(resultText(&result_buffer, result));
@@ -217,12 +211,12 @@ pub const Trace = struct {
             var disk_line_buffer: [256]u8 = undefined;
             const disk_prefix = std.fmt.bufPrint(&disk_line_buffer,
                 \\{{"time":{},"global_time":{},"event":"disk","node":{},"op":
-            , .{ pending_trace.local_time, global_time, pending_trace.node_id }) catch return;
+            , .{ pending_trace.start_time, global_time, pending_trace.node_id }) catch return;
             self.write(disk_prefix);
             self.writeJsonString(pending_trace.op);
             const middle = std.fmt.bufPrint(&disk_line_buffer,
                 \\,"start":{},"end":{},"detail":
-            , .{ pending_trace.local_time, local_time }) catch return;
+            , .{ pending_trace.start_time, global_time }) catch return;
             self.write(middle);
             self.writeJsonString(resultText(&result_buffer, result));
             self.write("}\n");