Rename OS-specific MemoryPressureMonitor implementations.

base/chromeos/memory_pressure_monitor_chromeos.cc

-// Copyright 2014 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 "base/chromeos/memory_pressure_monitor_chromeos.h"
-
-#include <fcntl.h>
-#include <sys/select.h>
-
-#include "base/metrics/histogram_macros.h"
-#include "base/posix/eintr_wrapper.h"
-#include "base/process/process_metrics.h"
-#include "base/single_thread_task_runner.h"
-#include "base/thread_task_runner_handle.h"
-#include "base/time/time.h"
-
-namespace base {
-
-namespace {
-
-// The time between memory pressure checks. While under critical pressure, this
-// is also the timer to repeat cleanup attempts.
-const int kMemoryPressureIntervalMs = 1000;
-
-// The time which should pass between two moderate memory pressure calls.
-const int kModerateMemoryPressureCooldownMs = 10000;
-
-// Number of event polls before the next moderate pressure event can be sent.
-const int kModerateMemoryPressureCooldown =
-    kModerateMemoryPressureCooldownMs / kMemoryPressureIntervalMs;
-
-// Threshold constants to emit pressure events.
-const int kNormalMemoryPressureModerateThresholdPercent = 60;
-const int kNormalMemoryPressureCriticalThresholdPercent = 95;
-const int kAggressiveMemoryPressureModerateThresholdPercent = 35;
-const int kAggressiveMemoryPressureCriticalThresholdPercent = 70;
-
-// The possible state for memory pressure level. The values should be in line
-// with values in MemoryPressureListener::MemoryPressureLevel and should be
-// updated if more memory pressure levels are introduced.
-enum MemoryPressureLevelUMA {
-  MEMORY_PRESSURE_LEVEL_NONE = 0,
-  MEMORY_PRESSURE_LEVEL_MODERATE,
-  MEMORY_PRESSURE_LEVEL_CRITICAL,
-  NUM_MEMORY_PRESSURE_LEVELS
-};
-
-// This is the file that will exist if low memory notification is available
-// on the device.  Whenever it becomes readable, it signals a low memory
-// condition.
-const char kLowMemFile[] = "/dev/chromeos-low-mem";
-
-// Converts a |MemoryPressureThreshold| value into a used memory percentage for
-// the moderate pressure event.
-int GetModerateMemoryThresholdInPercent(
-    MemoryPressureMonitorChromeOS::MemoryPressureThresholds thresholds) {
-  return thresholds == MemoryPressureMonitorChromeOS::
-                           THRESHOLD_AGGRESSIVE_CACHE_DISCARD ||
-         thresholds == MemoryPressureMonitorChromeOS::THRESHOLD_AGGRESSIVE
-             ? kAggressiveMemoryPressureModerateThresholdPercent
-             : kNormalMemoryPressureModerateThresholdPercent;
-}
-
-// Converts a |MemoryPressureThreshold| value into a used memory percentage for
-// the critical pressure event.
-int GetCriticalMemoryThresholdInPercent(
-    MemoryPressureMonitorChromeOS::MemoryPressureThresholds thresholds) {
-  return thresholds == MemoryPressureMonitorChromeOS::
-                           THRESHOLD_AGGRESSIVE_TAB_DISCARD ||
-         thresholds == MemoryPressureMonitorChromeOS::THRESHOLD_AGGRESSIVE
-             ? kAggressiveMemoryPressureCriticalThresholdPercent
-             : kNormalMemoryPressureCriticalThresholdPercent;
-}
-
-// Converts free percent of memory into a memory pressure value.
-MemoryPressureListener::MemoryPressureLevel GetMemoryPressureLevelFromFillLevel(
-    int actual_fill_level,
-    int moderate_threshold,
-    int critical_threshold) {
-  if (actual_fill_level < moderate_threshold)
-    return MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
-  return actual_fill_level < critical_threshold
-             ? MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE
-             : MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
-}
-
-// This function will be called less then once a second. It will check if
-// the kernel has detected a low memory situation.
-bool IsLowMemoryCondition(int file_descriptor) {
-  fd_set fds;
-  struct timeval tv;
-
-  FD_ZERO(&fds);
-  FD_SET(file_descriptor, &fds);
-
-  tv.tv_sec = 0;
-  tv.tv_usec = 0;
-
-  return HANDLE_EINTR(select(file_descriptor + 1, &fds, NULL, NULL, &tv)) > 0;
-}
-
-}  // namespace
-
-MemoryPressureMonitorChromeOS::MemoryPressureMonitorChromeOS(
-    MemoryPressureThresholds thresholds)
-    : current_memory_pressure_level_(
-          MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE),
-      moderate_pressure_repeat_count_(0),
-      moderate_pressure_threshold_percent_(
-          GetModerateMemoryThresholdInPercent(thresholds)),
-      critical_pressure_threshold_percent_(
-          GetCriticalMemoryThresholdInPercent(thresholds)),
-      low_mem_file_(HANDLE_EINTR(::open(kLowMemFile, O_RDONLY))),
-      weak_ptr_factory_(this) {
-  StartObserving();
-  LOG_IF(ERROR, !low_mem_file_.is_valid()) << "Cannot open kernel listener";
-}
-
-MemoryPressureMonitorChromeOS::~MemoryPressureMonitorChromeOS() {
-  StopObserving();
-}
-
-void MemoryPressureMonitorChromeOS::ScheduleEarlyCheck() {
-  ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, Bind(&MemoryPressureMonitorChromeOS::CheckMemoryPressure,
-                      weak_ptr_factory_.GetWeakPtr()));
-}
-
-MemoryPressureListener::MemoryPressureLevel
-MemoryPressureMonitorChromeOS::GetCurrentPressureLevel() const {
-  return current_memory_pressure_level_;
-}
-
-void MemoryPressureMonitorChromeOS::StartObserving() {
-  timer_.Start(FROM_HERE,
-               TimeDelta::FromMilliseconds(kMemoryPressureIntervalMs),
-               Bind(&MemoryPressureMonitorChromeOS::
-                        CheckMemoryPressureAndRecordStatistics,
-                    weak_ptr_factory_.GetWeakPtr()));
-}
-
-void MemoryPressureMonitorChromeOS::StopObserving() {
-  // If StartObserving failed, StopObserving will still get called.
-  timer_.Stop();
-}
-
-void MemoryPressureMonitorChromeOS::CheckMemoryPressureAndRecordStatistics() {
-  CheckMemoryPressure();
-
-  // Record UMA histogram statistics for the current memory pressure level.
-  MemoryPressureLevelUMA memory_pressure_level_uma(MEMORY_PRESSURE_LEVEL_NONE);
-  switch (current_memory_pressure_level_) {
-    case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE:
-      memory_pressure_level_uma = MEMORY_PRESSURE_LEVEL_NONE;
-      break;
-    case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE:
-      memory_pressure_level_uma = MEMORY_PRESSURE_LEVEL_MODERATE;
-      break;
-    case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL:
-      memory_pressure_level_uma = MEMORY_PRESSURE_LEVEL_CRITICAL;
-      break;
-  }
-
-  UMA_HISTOGRAM_ENUMERATION("ChromeOS.MemoryPressureLevel",
-                            memory_pressure_level_uma,
-                            NUM_MEMORY_PRESSURE_LEVELS);
-}
-
-void MemoryPressureMonitorChromeOS::CheckMemoryPressure() {
-  MemoryPressureListener::MemoryPressureLevel old_pressure =
-      current_memory_pressure_level_;
-
-  // If we have the kernel low memory observer, we use it's flag instead of our
-  // own computation (for now). Note that in "simulation mode" it can be null.
-  // TODO(skuhne): We need to add code which makes sure that the kernel and this
-  // computation come to similar results and then remove this override again.
-  // TODO(skuhne): Add some testing framework here to see how close the kernel
-  // and the internal functions are.
-  if (low_mem_file_.is_valid() && IsLowMemoryCondition(low_mem_file_.get())) {
-    current_memory_pressure_level_ =
-        MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
-  } else {
-    current_memory_pressure_level_ = GetMemoryPressureLevelFromFillLevel(
-        GetUsedMemoryInPercent(),
-        moderate_pressure_threshold_percent_,
-        critical_pressure_threshold_percent_);
-
-    // When listening to the kernel, we ignore the reported memory pressure
-    // level from our own computation and reduce critical to moderate.
-    if (low_mem_file_.is_valid() &&
-        current_memory_pressure_level_ ==
-        MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL) {
-      current_memory_pressure_level_ =
-          MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE;
-    }
-  }
-
-  // In case there is no memory pressure we do not notify.
-  if (current_memory_pressure_level_ ==
-      MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE) {
-    return;
-  }
-  if (old_pressure == current_memory_pressure_level_) {
-    // If the memory pressure is still at the same level, we notify again for a
-    // critical level. In case of a moderate level repeat however, we only send
-    // a notification after a certain time has passed.
-    if (current_memory_pressure_level_ ==
-        MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE &&
-          ++moderate_pressure_repeat_count_ <
-              kModerateMemoryPressureCooldown) {
-      return;
-    }
-  } else if (current_memory_pressure_level_ ==
-               MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE &&
-             old_pressure ==
-               MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL) {
-    // When we reducing the pressure level from critical to moderate, we
-    // restart the timeout and do not send another notification.
-    moderate_pressure_repeat_count_ = 0;
-    return;
-  }
-  moderate_pressure_repeat_count_ = 0;
-  MemoryPressureListener::NotifyMemoryPressure(current_memory_pressure_level_);
-}
-
-// Gets the used ChromeOS memory in percent.
-int MemoryPressureMonitorChromeOS::GetUsedMemoryInPercent() {
-  base::SystemMemoryInfoKB info;
-  if (!base::GetSystemMemoryInfo(&info)) {
-    VLOG(1) << "Cannot determine the free memory of the system.";
-    return 0;
-  }
-  // TODO(skuhne): Instead of adding the kernel memory pressure calculation
-  // logic here, we should have a kernel mechanism similar to the low memory
-  // notifier in ChromeOS which offers multiple pressure states.
-  // To track this, we have crbug.com/381196.
-
-  // 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;
-
-  // The total memory we have is the "real memory" plus the virtual (z)ram.
-  int total_memory = info.total + info.swap_total / kSwapWeight;
-
-  // The kernel internally uses 50MB.
-  const int kMinFileMemory = 50 * 1024;
-
-  // Most file memory can be easily reclaimed.
-  int file_memory = info.active_file + info.inactive_file;
-  // unless it is dirty or it's a minimal portion which is required.
-  file_memory -= info.dirty + kMinFileMemory;
-
-  // Available memory is the sum of free, swap and easy reclaimable memory.
-  int available_memory =
-      info.free + info.swap_free / kSwapWeight + file_memory;
-
-  DCHECK(available_memory < total_memory);
-  int percentage = ((total_memory - available_memory) * 100) / total_memory;
-  return percentage;
-}
-
-}  // namespace base