Print scheduler details (ExecutionContext)

src/perf_tools/scheduler_trace.cr

@@ -0,0 +1,134 @@
+require "./common"
+
+module PerfTools::SchedulerTrace
+  {% if flag?(:unix) %}
+    # Installs a signal handler to call `.print_runtime_status` on demand.
+    #
+    # Uses `SIGUSR1` by default but you may configure another signal, for
+    # example `LibC::SIGRTMIN + 7`. You may also register multiple signals, one
+    # with fiber detail and the another without for example.
+    def self.on(signal : Int32 = Signal::USR1.value, details = false) : Nil
+      # not using Signal#trap so the signal will be handled directly instead
+      # of through the event loop that may have to wait (or be blocked in
+      # the worst case):
+      action = LibC::Sigaction.new
+      action.sa_flags = LibC::SA_RESTART
+      action.sa_sigaction = LibC::SigactionHandlerT.new do |_, _, _|
+        print_runtime_status(details)
+      end
+      LibC.sigemptyset(pointerof(action.@sa_mask))
+      LibC.sigaction(signal, pointerof(action), nil)
+    end
+  {% end %}
+
+  # Starts a thread that will call `.print_runtime_status` every *time* until
+  # the program terminates.
+  def self.every(time : Time::Span, details = false) : Nil
+    Thread.new("PerfToolsSched") do
+      loop do
+        Thread.sleep(time)
+        print_runtime_status(details)
+      end
+    end
+  end
+
+  # Stops the world, prints the status of all runtime schedulers, then resumes
+  # the world.
+  #
+  # Set `details` to true to print individual fiber details.
+  def self.print_runtime_status(details = false) : Nil
+    Thread.stop_world
+
+    Crystal::System.print_error("sched.details time=%u\n", Crystal::System::Time.ticks)
+
+    ExecutionContext.unsafe_each do |execution_context|
+      print_runtime_status(execution_context, details)
+    end
+
+    Thread.start_world
+  end
+
+  private def self.print_runtime_status(execution_context : ExecutionContext::MultiThreaded, details = false) : Nil
+    Crystal::System.print_error("%s name=%s global_queue.size=%d\n",
+      execution_context.class.name,
+      execution_context.name,
+      execution_context.@global_queue.size)
+
+    execution_context.@threads.each do |thread|
+      print_runtime_status(thread, details)
+    end
+
+    return unless details
+
+    Fiber.unsafe_each do |fiber|
+      if fiber.execution_context? == execution_context
+        print_runtime_status(fiber)
+      end
+    end
+  end
+
+  private def self.print_runtime_status(execution_context : ExecutionContext::SingleThreaded, details = false) : Nil
+    Crystal::System.print_error("%s name=%s global_queue.size=%d\n",
+      execution_context.class.name,
+      execution_context.name,
+      execution_context.@global_queue.size)
+
+    print_runtime_status(execution_context.@thread, details)
+
+    return unless details
+
+    Fiber.unsafe_each do |fiber|
+      if fiber.execution_context? == execution_context
+        print_runtime_status(fiber)
+      end
+    end
+  end
+
+  private def self.print_runtime_status(execution_context : ExecutionContext::Isolated, details = false) : Nil
+    Crystal::System.print_error("%s name=%s\n", execution_context.class.name, execution_context.name)
+    print_runtime_status(execution_context.@thread, details = false)
+  end
+
+  private def self.print_runtime_status(thread : Thread, details = false) : Nil
+    thread_handle =
+      {% if flag?(:linux) %}
+        Pointer(Void).new(thread.@system_handle)
+      {% else %}
+        thread.@system_handle
+      {% end %}
+
+    case scheduler = thread.current_scheduler?
+    when ExecutionContext::MultiThreaded::Scheduler
+      Crystal::System.print_error("  Scheduler name=%s thread=%p local_queue.size=%u status=%s\n",
+        scheduler.name,
+        thread_handle,
+        scheduler.@runnables.size,
+        scheduler.status)
+    when ExecutionContext::SingleThreaded
+      Crystal::System.print_error("  Scheduler name=%s thread=%p local_queue.size=%u status=%s\n",
+        scheduler.name,
+        thread_handle,
+        scheduler.@runnables.size,
+        scheduler.status)
+    when ExecutionContext::Isolated
+      Crystal::System.print_error("  Scheduler name=%s thread=%p status=%s\n",
+        scheduler.name,
+        thread_handle,
+        scheduler.status)
+    end
+
+    return unless details
+
+    if fiber = thread.current_fiber?
+      Crystal::System.print_error("    Fiber %p name=%s status=running\n", fiber.as(Void*), fiber.name)
+    end
+  end
+
+  # TODO: print the fiber status: running, queued (local, global), sleeping, suspended, ...
+  private def self.print_runtime_status(fiber : Fiber) : Nil
+    Crystal::System.print_error("  Fiber %p name=%s\n", fiber.as(Void*), fiber.name)
+  end
+
+  # private def self.print_runtime_status(arg : Nil, details = false) : Nil
+  # end
+end