//net/base/task

This directory provides a mechanism for obtaining base::SingleThreadTaskRunner instances that are integrated with task scheduling and prioritization system of the embedder process (e.g network service).

Overview

The primary API offered is:

namespace net {

const scoped_refptr<base::SingleThreadTaskRunner>& GetTaskRunner(
    RequestPriority priority);

}  // namespace net

This function allows code (typically running on the network thread or interacting closely with network operations) to post tasks with a specific net::RequestPriority.

Integration with Network Service Scheduler

The NetworkServiceTaskScheduler (located in //services/network/scheduler/) is responsible for setting up and managing the actual task queues on the network service thread, including a high-priority queue.

During its initialization (specifically in SetupNetTaskRunners()), the NetworkServiceTaskScheduler populates net::internal::GetTaskRunnerGlobals().high_priority_task_runner with the task runner associated with its own high-priority queue.

This ensures that when net::GetTaskRunner(net::HIGHEST) is called, tasks posted to the returned runner are routed to the network service's designated high-priority processing queue.

Usage

Components that need to schedule work on the network thread with specific network-related priorities should use net::GetTaskRunner(). This helps ensure that critical network tasks (like those with net::HIGHEST priority) are processed appropriately by the network service's scheduler.

If RequestPriority is unavailable or you are unsure which priority should be used, continue to use base::SingleThreadTaskRunner::GetCurrentDefault() as usual. This is currently equivalent to calling net::GetTaskRunner(priority) for any priority except net::HIGHEST.

Task execution order is not guaranteed if you post tasks to different queues. If you need posted tasks to be executed in order, use the same task runner.

The mapping of RequestPriority to underlying TaskQueue is subject to change. Please do not write code that depends on this mapping.