Adding flag to specify the used memory pressure strategy

This CL adds a flag to change the memory pressure event thresholds. This flag will later on then used in a finch experiment to test the influence of the thresholds on the system.

BUG=449374
TEST=-

Review URL: https://codereview.chromium.org/803443006

Cr-Commit-Position: refs/heads/master@{#312499}

base/chromeos/memory_pressure_observer_chromeos.cc

@@ -24,25 +24,56 @@ const int kModerateMemoryPressureCooldown =
     kModerateMemoryPressureCooldownMs / kMemoryPressureIntervalMs;
 
 // Threshold constants to emit pressure events.
-const int kMemoryPressureModerateThresholdPercent = 70;
-const int kMemoryPressureCriticalThresholdPercent = 90;
+const int kNormalMemoryPressureModerateThresholdPercent = 60;
+const int kNormalMemoryPressureCriticalThresholdPercent = 90;
+const int kAggressiveMemoryPressureModerateThresholdPercent = 35;
+const int kAggressiveMemoryPressureCriticalThresholdPercent = 70;
+
+// Converts a |MemoryPressureThreshold| value into a used memory percentage for
+// the moderate pressure event.
+int GetModerateMemoryThresholdInPercent(
+    MemoryPressureObserverChromeOS::MemoryPressureThresholds thresholds) {
+  return thresholds == MemoryPressureObserverChromeOS::
+                           THRESHOLD_AGGRESSIVE_CACHE_DISCARD ||
+         thresholds == MemoryPressureObserverChromeOS::THRESHOLD_AGGRESSIVE
+             ? kAggressiveMemoryPressureModerateThresholdPercent
+             : kNormalMemoryPressureModerateThresholdPercent;
+}
+
+// Converts a |MemoryPressureThreshold| value into a used memory percentage for
+// the critical pressure event.
+int GetCriticalMemoryThresholdInPercent(
+    MemoryPressureObserverChromeOS::MemoryPressureThresholds thresholds) {
+  return thresholds == MemoryPressureObserverChromeOS::
+                           THRESHOLD_AGGRESSIVE_TAB_DISCARD ||
+         thresholds == MemoryPressureObserverChromeOS::THRESHOLD_AGGRESSIVE
+             ? kAggressiveMemoryPressureCriticalThresholdPercent
+             : kNormalMemoryPressureCriticalThresholdPercent;
+}
 
 // Converts free percent of memory into a memory pressure value.
 MemoryPressureListener::MemoryPressureLevel GetMemoryPressureLevelFromFillLevel(
-    int memory_fill_level) {
-  if (memory_fill_level < kMemoryPressureModerateThresholdPercent)
+    int actual_fill_level,
+    int moderate_threshold,
+    int critical_threshold) {
+  if (actual_fill_level < moderate_threshold)
     return MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
-  return memory_fill_level < kMemoryPressureCriticalThresholdPercent ?
-      MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE :
-      MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
+  return actual_fill_level < critical_threshold
+             ? MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE
+             : MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
 }
 
 }  // namespace
 
-MemoryPressureObserverChromeOS::MemoryPressureObserverChromeOS()
+MemoryPressureObserverChromeOS::MemoryPressureObserverChromeOS(
+    MemoryPressureThresholds thresholds)
     : current_memory_pressure_level_(
-        MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE),
+          MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE),
       moderate_pressure_repeat_count_(0),
+      moderate_pressure_threshold_percent_(
+          GetModerateMemoryThresholdInPercent(thresholds)),
+      critical_pressure_threshold_percent_(
+          GetCriticalMemoryThresholdInPercent(thresholds)),
       weak_ptr_factory_(this) {
   StartObserving();
 }
@@ -74,7 +105,9 @@ void MemoryPressureObserverChromeOS::CheckMemoryPressure() {
   MemoryPressureListener::MemoryPressureLevel old_pressure =
       current_memory_pressure_level_;
   current_memory_pressure_level_ =
-      GetMemoryPressureLevelFromFillLevel(GetUsedMemoryInPercent());
+      GetMemoryPressureLevelFromFillLevel(GetUsedMemoryInPercent(),
+                                          moderate_pressure_threshold_percent_,
+                                          critical_pressure_threshold_percent_);
   // In case there is no memory pressure we do not notify.
   if (current_memory_pressure_level_ ==
       MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE) {

base/chromeos/memory_pressure_observer_chromeos.h

@@ -27,7 +27,27 @@ class BASE_EXPORT MemoryPressureObserverChromeOS {
  public:
   using GetUsedMemoryInPercentCallback = int (*)();
 
-  MemoryPressureObserverChromeOS();
+  // There are two memory pressure events:
+  // MODERATE - which will mainly release caches.
+  // CRITICAL - which will discard tabs.
+  // The |MemoryPressureThresholds| enum selects the strategy of firing these
+  // events: A conservative strategy will keep as much content in memory as
+  // possible (causing the system to swap to zram) and an aggressive strategy
+  // will release memory earlier to avoid swapping.
+  enum MemoryPressureThresholds {
+    // Use the system default.
+    THRESHOLD_DEFAULT = 0,
+    // Try to keep as much content in memory as possible.
+    THRESHOLD_CONSERVATIVE = 1,
+    // Discard caches earlier, allowing to keep more tabs in memory.
+    THRESHOLD_AGGRESSIVE_CACHE_DISCARD = 2,
+    // Discard tabs earlier, allowing the system to get faster.
+    THRESHOLD_AGGRESSIVE_TAB_DISCARD = 3,
+    // Discard caches and tabs earlier to allow the system to be faster.
+    THRESHOLD_AGGRESSIVE = 4
+  };
+
+  explicit MemoryPressureObserverChromeOS(MemoryPressureThresholds thresholds);
   virtual ~MemoryPressureObserverChromeOS();
 
   // Redo the memory pressure calculation soon and call again if a critical
@@ -71,6 +91,10 @@ class BASE_EXPORT MemoryPressureObserverChromeOS {
   // gets used to count the number of events since the last event occured.
   int moderate_pressure_repeat_count_;
 
+  // The thresholds for moderate and critical pressure.
+  const int moderate_pressure_threshold_percent_;
+  const int critical_pressure_threshold_percent_;
+
   base::WeakPtrFactory<MemoryPressureObserverChromeOS> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryPressureObserverChromeOS);

base/chromeos/memory_pressure_observer_chromeos_unittest.cc

@@ -42,7 +42,10 @@ bool WasOnMemoryPressureCalled() {
 
 class TestMemoryPressureObserver : public MemoryPressureObserverChromeOS {
  public:
-  TestMemoryPressureObserver() : memory_in_percent_override_(0) {
+  TestMemoryPressureObserver() :
+    MemoryPressureObserverChromeOS(
+        MemoryPressureObserverChromeOS::THRESHOLD_DEFAULT),
+    memory_in_percent_override_(0) {
     // Disable any timers which are going on and set a special memory reporting
     // function.
     StopObserving();

chrome/app/chromeos_strings.grdp

@@ -1129,6 +1129,24 @@ Press any key to continue exploring.
   <message name="IDS_FLAGS_DISABLE_MEMORY_PRESSURE_DESCRIPTION" desc="Description for the flag to disable memory pressure handling on ChromeOS.">
     Disable enhanced memory pressure handling on ChromeOS.
   </message>
+  <message name="IDS_FLAGS_MEMORY_PRESSURE_THRESHOLD_NAME" desc="Name for the flag which specifies which memory pressure strategy should be used on ChromeOS.">
+    Memory discard strategy for advanced pressure handling
+  </message>
+  <message name="IDS_FLAGS_MEMORY_PRESSURE_THRESHOLD_DESCRIPTION" desc="Description for the flag which specifies which memory pressure strategy should be used on ChromeOS.">
+    Memory discarding strategy to use
+  </message>
+  <message name="IDS_FLAGS_CONSERVATIVE_THRESHOLDS" desc="The value of the Memory pressure for ChromeOS which requests conservative thresholds.">
+    Conservative memory pressure release strategy
+  </message>
+  <message name="IDS_FLAGS_AGGRESSIVE_CACHE_DISCARD_THRESHOLDS" desc="The value of the Memory pressure thresholds for ChromeOS which use an aggressive cache release strategy.">
+    Aggressive cache release strategy
+  </message>
+  <message name="IDS_FLAGS_AGGRESSIVE_TAB_DISCARD_THRESHOLDS" desc="The value of the Memory pressure thresholds for ChromeOS which uses an aggressive tab release strategy.">
+    Aggressive tab release strategy
+  </message>
+  <message name="IDS_FLAGS_AGGRESSIVE_THRESHOLDS" desc="The value of the Memory pressure thresholds for ChromeOS which use an aggressive release strategy.">
+    Aggressive tab and cache release strategy
+  </message>
   <message name="IDS_FLAGS_WAKE_ON_PACKETS_NAME" desc="Name for the flag to enable wake on packets.">
     Wake On Packets
   </message>

chrome/browser/about_flags.cc

@@ -284,6 +284,20 @@ const Experiment::Choice kEnableGpuRasterizationChoices[] = {
     switches::kForceGpuRasterization, "" },
 };
 
+#if defined(OS_CHROMEOS)
+const Experiment::Choice kMemoryPressureThresholdChoices[] = {
+  { IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT, "", "" },
+  { IDS_FLAGS_CONSERVATIVE_THRESHOLDS,
+    chromeos::switches::kMemoryPressureThresholds, "1" },
+  { IDS_FLAGS_AGGRESSIVE_CACHE_DISCARD_THRESHOLDS,
+    chromeos::switches::kMemoryPressureThresholds, "2" },
+  { IDS_FLAGS_AGGRESSIVE_TAB_DISCARD_THRESHOLDS,
+    chromeos::switches::kMemoryPressureThresholds, "3" },
+  { IDS_FLAGS_AGGRESSIVE_THRESHOLDS,
+    chromeos::switches::kMemoryPressureThresholds, "4" },
+};
+#endif
+
 // We're using independent flags here (as opposed to a common flag with
 // different values) to be able to enable/disable the entire experience
 // associated with this feature server-side from the FieldTrial (the complete
@@ -2002,6 +2016,13 @@ const Experiment kExperiments[] = {
     kOsCrOS,
     SINGLE_VALUE_TYPE(chromeos::switches::kDisableMemoryPressureSystemChromeOS)
   },
+  {
+    "memory-pressure-thresholds",
+    IDS_FLAGS_MEMORY_PRESSURE_THRESHOLD_NAME,
+    IDS_FLAGS_MEMORY_PRESSURE_THRESHOLD_DESCRIPTION,
+    kOsCrOS,
+    MULTI_VALUE_TYPE(kMemoryPressureThresholdChoices)
+  },
   {
     "wake-on-packets",
     IDS_FLAGS_WAKE_ON_PACKETS_NAME,

chromeos/chromeos_switches.cc

@@ -213,6 +213,10 @@ const char kLoginProfile[] = "login-profile";
 // Specifies the user which is already logged in.
 const char kLoginUser[] = "login-user";
 
+// The memory pressure thresholds selection which is used to decide when a
+// memory pressure event needs to get fired.
+const char kMemoryPressureThresholds[] = "memory-pressure-thresholds";
+
 // Enables natural scroll by default.
 const char kNaturalScrollDefault[] = "enable-natural-scroll-default";
 
@@ -292,5 +296,28 @@ bool WakeOnWifiEnabled() {
   return !base::CommandLine::ForCurrentProcess()->HasSwitch(kDisableWakeOnWifi);
 }
 
+base::MemoryPressureObserverChromeOS::MemoryPressureThresholds
+GetMemoryPressureThresholds() {
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          kMemoryPressureThresholds)) {
+    return base::MemoryPressureObserverChromeOS::THRESHOLD_DEFAULT;
+  }
+  const std::string option =
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          kMemoryPressureThresholds);
+  if (option == "1") {
+    return base::MemoryPressureObserverChromeOS::THRESHOLD_CONSERVATIVE;
+  }
+  if (option == "2") {
+    return base::MemoryPressureObserverChromeOS::
+        THRESHOLD_AGGRESSIVE_CACHE_DISCARD;
+  }
+  if (option == "3") {
+    return base::MemoryPressureObserverChromeOS::
+        THRESHOLD_AGGRESSIVE_TAB_DISCARD;
+  }
+  return base::MemoryPressureObserverChromeOS::THRESHOLD_AGGRESSIVE;
+}
+
 }  // namespace switches
 }  // namespace chromeos

chromeos/chromeos_switches.h

@@ -5,6 +5,7 @@
 #ifndef CHROMEOS_CHROMEOS_SWITCHES_H_
 #define CHROMEOS_CHROMEOS_SWITCHES_H_
 
+#include "base/chromeos/memory_pressure_observer_chromeos.h"
 #include "chromeos/chromeos_export.h"
 
 namespace chromeos {
@@ -82,6 +83,7 @@ CHROMEOS_EXPORT extern const char kIgnoreUserProfileMappingForTests[];
 CHROMEOS_EXPORT extern const char kLoginManager[];
 CHROMEOS_EXPORT extern const char kLoginProfile[];
 CHROMEOS_EXPORT extern const char kLoginUser[];
+CHROMEOS_EXPORT extern const char kMemoryPressureThresholds[];
 CHROMEOS_EXPORT extern const char kNaturalScrollDefault[];
 CHROMEOS_EXPORT extern const char kOobeGuestSession[];
 CHROMEOS_EXPORT extern const char kOobeSkipPostLogin[];
@@ -97,6 +99,9 @@ CHROMEOS_EXPORT extern const char kEnableCaptivePortalBypassProxy[];
 
 CHROMEOS_EXPORT bool WakeOnWifiEnabled();
 
+CHROMEOS_EXPORT base::MemoryPressureObserverChromeOS::MemoryPressureThresholds
+GetMemoryPressureThresholds();
+
 }  // namespace switches
 }  // namespace chromeos
 

content/browser/browser_main_loop.cc

@@ -490,7 +490,8 @@ void BrowserMainLoop::MainMessageLoopStart() {
 #if defined(OS_CHROMEOS)
   if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
           chromeos::switches::kDisableMemoryPressureSystemChromeOS)) {
-    memory_pressure_observer_.reset(new base::MemoryPressureObserverChromeOS);
+    memory_pressure_observer_.reset(new base::MemoryPressureObserverChromeOS(
+        chromeos::switches::GetMemoryPressureThresholds()));
   }
 #endif
 

tools/metrics/histograms/histograms.xml

@@ -50408,6 +50408,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="121858954" label="enable-supervised-user-safesites"/>
   <int value="125934378" label="enable-password-link"/>
   <int value="147373243" label="enable-deferred-image-decoding"/>
+  <int value="180074362" label="memory-pressure-thresholds"/>
   <int value="203776499" label="enable-virtual-keyboard-overscroll"/>
   <int value="270267831" label="enable-scripts-require-action"/>
   <int value="278756320" label="disable-app-list-app-info"/>