Using the new MemoryPressureListener instead of the LowMemoryObserver when the enhanced memory mana…

base/chromeos/memory_pressure_observer_chromeos.cc

Index: base/chromeos/memory_pressure_observer_chromeos.cc
diff --git a/base/chromeos/memory_pressure_observer_chromeos.cc b/base/chromeos/memory_pressure_observer_chromeos.cc
index 22291da09ba9191054f26eb3c8bce70470917389..bfac8d7566249027cb6b552b4dcedf208bf97431 100644
--- a/base/chromeos/memory_pressure_observer_chromeos.cc
+++ b/base/chromeos/memory_pressure_observer_chromeos.cc
@@ -4,6 +4,7 @@
 
 #include "base/chromeos/memory_pressure_observer_chromeos.h"
 
+#include "base/message_loop/message_loop.h"
 #include "base/process/process_metrics.h"
 #include "base/time/time.h"
 
@@ -11,15 +12,27 @@ namespace base {
 
 namespace {
 
-// The time between memory pressure checks.
+// The time between memory pressure checks. While under critical pressure, this
+// is also the timer to repeat cleanup attempts.
 const int kMemoryPressureIntervalInMS = 1000;

[James Cook, 2014/12/20 00:27:46]

nit: I would rename to kMemoryPressureIntervalMs for consistency with below.

[Mr4D (OOO till 08-26), 2014/12/20 03:01:04]

Done.

 
+// 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 / kMemoryPressureIntervalInMS;
+
+// Threshold constants to emit pressure events.
+const int kMemoryPressureModerateThresholdPercent = 70;
+const int kMemoryPressureCriticalThresholdPercent = 90;
+
 // Converts free percent of memory into a memory pressure value.
 MemoryPressureListener::MemoryPressureLevel GetMemoryPressureLevelFromFillLevel(
     int memory_fill_level) {
-  if (memory_fill_level < 70)
+  if (memory_fill_level < kMemoryPressureModerateThresholdPercent)
     return MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
-  return memory_fill_level < 90 ?
+  return memory_fill_level < kMemoryPressureCriticalThresholdPercent ?
       MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE :
       MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
 }
@@ -66,7 +79,10 @@ int GetUsedMemoryInPercent() {
 
 MemoryPressureObserverChromeOS::MemoryPressureObserverChromeOS()
     : current_memory_pressure_level_(
-        MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE) {
+        MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE),
+      used_memory_in_percent_(GetUsedMemoryInPercent),

[James Cook, 2014/12/20 00:27:46]

Instead of doing this you could rename the function above to
GetUsedMemoryInPercentImpl() and add a virtual function:

virtual int GetUsedMemoryInPercent() {
  return GetUsedMemoryInPercentImpl();
}

Then subclass this call in the test.  Might be cleaner.

[Mr4D (OOO till 08-26), 2014/12/20 03:01:04]

Oh my. I must have been blind. In deed! Done!

+      moderate_pressure_repeat_count_(0),
+      weak_ptr_factory_(this) {
   StartObserving();
 }
 
@@ -74,11 +90,25 @@ MemoryPressureObserverChromeOS::~MemoryPressureObserverChromeOS() {
   StopObserving();
 }
 
+void MemoryPressureObserverChromeOS::ScheduleEarlyCheck() {
+  MessageLoop::current()->PostTask(
+      FROM_HERE,
+      Bind(&MemoryPressureObserverChromeOS::CheckMemoryPressure,
+           weak_ptr_factory_.GetWeakPtr()));
+}
+
+void
+MemoryPressureObserverChromeOS::SetGetUsedMemoryInPercentCallbackForUnittest(
+    MemoryPressureObserverChromeOS::GetUsedMemoryInPercentCallback callback) {
+  DCHECK(callback);
+  used_memory_in_percent_ = callback;
+}
+
 void MemoryPressureObserverChromeOS::StartObserving() {
   timer_.Start(FROM_HERE,
-               base::TimeDelta::FromMilliseconds(kMemoryPressureIntervalInMS),
-               base::Bind(&MemoryPressureObserverChromeOS::CheckMemoryPressure,
-                          base::Unretained(this)));
+               TimeDelta::FromMilliseconds(kMemoryPressureIntervalInMS),
+               Bind(&MemoryPressureObserverChromeOS::CheckMemoryPressure,
+                    weak_ptr_factory_.GetWeakPtr()));
 }
 
 void MemoryPressureObserverChromeOS::StopObserving() {
@@ -89,14 +119,34 @@ void MemoryPressureObserverChromeOS::StopObserving() {
 void MemoryPressureObserverChromeOS::CheckMemoryPressure() {
   MemoryPressureListener::MemoryPressureLevel old_pressure =
       current_memory_pressure_level_;
-  MemoryPressureListener::MemoryPressureLevel new_pressure =
-      GetMemoryPressureLevelFromFillLevel(GetUsedMemoryInPercent());
-  if (old_pressure != new_pressure) {
-    current_memory_pressure_level_ = new_pressure;
-    // Everything but NONE will be sent to the listener.
-    if (new_pressure != MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE)
-      MemoryPressureListener::NotifyMemoryPressure(new_pressure);
+  current_memory_pressure_level_ =
+      GetMemoryPressureLevelFromFillLevel(used_memory_in_percent_());
+  // In cas there is no memory pressure we do not notify.

[James Cook, 2014/12/20 00:27:46]

cas -> case

[Mr4D (OOO till 08-26), 2014/12/20 03:01:04]

Done.

+  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_);
 }
 
 }  // namespace base