// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

module blink.mojom;

import "mojo/public/mojom/base/shared_memory.mojom";

// There are two phases to estimate a near-OOM situation. First phase takes
// place in the browser process. When the browser detects a high memory
// pressure it starts the second phase in the foreground renderer process,
// as the renderer has the best knowledge about memory usage of pages.
// The renderer schedules tasks to check memory workload from pages. If the
// workload exceeds a threshold the renderer notifies that a high memory usage
// is detected.

// Browser side interface for OOM intervention. This interface is used to check
// high memory usage in a renderer.
interface OomInterventionHost {
  // Called when a renderer detects high memory usage. |intervention_triggered|
  // is set to true when the OOM intervention is activated in the renderer.
  OnHighMemoryUsage(bool intervention_triggered);
};

// Arguments set by field trials to configure various thresholds for detecting
// OOM. Setting a threshold to 0 means that OOM detection will not consider
// that threshold.
struct DetectionArgs {
  // Limit on V8 + BlinkGC + PartitionAlloc.
  uint64 blink_workload_threshold;

  // Limit on total private footprint of the process.
  uint64 private_footprint_threshold;

  // Limit on total swap footprint of the process.
  uint64 swap_threshold;

  // Limit on total virtual memory used by the process.
  uint64 virtual_memory_thresold;
};

// Renderer side interface for OOM intervention. An instance of this interface
// will be created when the browser gets a high memory pressure signal.
// It monitors memory usage in renderer side to detect near-OOM situation.
interface OomIntervention {
  // Starts monitoring memory usage in renderer side. When the renderer's
  // memory usage exceeds |memory_workload_threshold| (in bytes) the renderer
  // calls host->OnHighMemoryUsage(). The renderer also triggers OOM
  // intervention when |trigger_intervention| is true. |shared_metrics_buffer|
  // stores the OomInterventionMetrics struct in shared memory. The buffer is
  // expected to be upated very often with memory metrics.
  StartDetection(OomInterventionHost host,
                 mojo_base.mojom.UnsafeSharedMemoryRegion shared_metrics_buffer,
                 DetectionArgs detection_args,
                 bool trigger_intervention);
};