Update MemoryMonitorChromeOS

content/browser/memory/memory_monitor_chromeos.cc

 // Copyright (c) 2016 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.
 
 #include "content/browser/memory/memory_monitor_chromeos.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/process/process_metrics.h"
 
 namespace content {
 
 namespace {
 
 // The number of bits to shift to convert KiB to MiB.
 const int kShiftKiBtoMiB = 10;
 
 }  // namespace
 
 MemoryMonitorChromeOS::MemoryMonitorChromeOS(MemoryMonitorDelegate* delegate)
     : delegate_(delegate) {}
 
 MemoryMonitorChromeOS::~MemoryMonitorChromeOS() {}
 
 int MemoryMonitorChromeOS::GetFreeMemoryUntilCriticalMB() {
   base::SystemMemoryInfoKB mem_info = {};
   delegate_->GetSystemMemoryInfo(&mem_info);
 
-  // The available memory consists of "real" and virtual (z)ram memory.
-  // Since swappable memory uses a non pre-deterministic compression and
-  // the compression creates its own "dynamic" in the system, it gets
-  // de-emphasized by the |kSwapWeight| factor.
-  const int kSwapWeight = 4;
+  // Use available free memory provided by the OS if the OS supports it.
+  if (mem_info.available > 0)
+    return mem_info.available >> kShiftKiBtoMiB;
 
   // The kernel internally uses 50MB.
   const int kMinFileMemory = 50 * 1024;
 
   // Most file memory can be easily reclaimed.
   int file_memory = mem_info.active_file + mem_info.inactive_file;
   // unless it is dirty or it's a minimal portion which is required.
   file_memory -= mem_info.dirty + kMinFileMemory;
 
-  // Available memory is the sum of free, swap and easy reclaimable memory.
-  return (mem_info.free + mem_info.swap_free / kSwapWeight + file_memory) >>
-         kShiftKiBtoMiB;
+  // Available memory is the sum of free and easy reclaimable memory.
+  return (mem_info.free + file_memory) >> kShiftKiBtoMiB;
 }
 
 // static
 std::unique_ptr<MemoryMonitorChromeOS> MemoryMonitorChromeOS::Create(
     MemoryMonitorDelegate* delegate) {
   return base::MakeUnique<MemoryMonitorChromeOS>(delegate);
 }
 
 // Implementation of factory function defined in memory_monitor.h.
 std::unique_ptr<MemoryMonitor> CreateMemoryMonitor() {
   return MemoryMonitorChromeOS::Create(MemoryMonitorDelegate::GetInstance());
 }
 
 }  // namespace content