Add available memory histograms

This should help inform the choice of the heuristic memory saver
thresholds

Bug: 1420344
Change-Id: Ic178c327c625e90558aab6db27a8e5639447d281
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4361971
Reviewed-by: Joe Mason <joenotcharles@google.com>
Commit-Queue: Anthony Vallée-Dubois <anthonyvd@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1122551}

Author: Anthony Vallee-Dubois

chrome/browser/performance_manager/metrics/metrics_provider.cc

@@ -5,6 +5,8 @@
 #include "chrome/browser/performance_manager/metrics/metrics_provider.h"
 
 #include "base/metrics/histogram_functions.h"
+#include "base/system/sys_info.h"
+#include "base/timer/timer.h"
 #include "chrome/browser/performance_manager/public/user_tuning/user_performance_tuning_manager.h"
 #include "components/performance_manager/public/user_tuning/prefs.h"
 #include "components/prefs/pref_service.h"
@@ -15,6 +17,7 @@ namespace {
 
 MetricsProvider* g_metrics_provider = nullptr;
 
+uint64_t kBytesPerMb = 1024 * 1024;
 }
 
 // static
@@ -65,6 +68,11 @@ MetricsProvider::MetricsProvider(PrefService* local_state)
     : local_state_(local_state) {
   DCHECK(!g_metrics_provider);
   g_metrics_provider = this;
+
+  available_memory_metrics_timer_.Start(
+      FROM_HERE, base::Minutes(2),
+      base::BindRepeating(&MetricsProvider::RecordAvailableMemoryMetrics,
+                          base::Unretained(this)));
 }
 
 void MetricsProvider::OnBatterySaverModeChanged(bool is_active) {
@@ -114,4 +122,14 @@ MetricsProvider::EfficiencyMode MetricsProvider::ComputeCurrentMode() const {
   return EfficiencyMode::kNormal;
 }
 
+void MetricsProvider::RecordAvailableMemoryMetrics() {
+  auto available_bytes = base::SysInfo::AmountOfAvailablePhysicalMemory();
+  auto total_bytes = base::SysInfo::AmountOfPhysicalMemory();
+
+  base::UmaHistogramMemoryLargeMB("Memory.Experimental.AvailableMemoryMB",
+                                  available_bytes / kBytesPerMb);
+  base::UmaHistogramPercentage("Memory.Experimental.AvailableMemoryPercent",
+                               available_bytes * 100 / total_bytes);
+}
+
 }  // namespace performance_manager

chrome/browser/performance_manager/metrics/metrics_provider.h

@@ -60,13 +60,17 @@ class MetricsProvider : public ::metrics::MetricsProvider,
   void OnTuningModesChanged();
   EfficiencyMode ComputeCurrentMode() const;
 
+  void RecordAvailableMemoryMetrics();
+
   PrefChangeRegistrar pref_change_registrar_;
   const raw_ptr<PrefService> local_state_;
   EfficiencyMode current_mode_ = EfficiencyMode::kNormal;
 
   bool battery_saver_enabled_ = false;
 
   bool initialized_ = false;
+
+  base::RepeatingTimer available_memory_metrics_timer_;
 };
 
 }  // namespace performance_manager

tools/metrics/histograms/metadata/memory/histograms.xml

@@ -524,6 +524,31 @@ chromium-metrics-reviews@google.com.
   </summary>
 </histogram>
 
+<histogram name="Memory.Experimental.AvailableMemoryMB" units="MB"
+    expires_after="2023-09-22">
+  <owner>anthonyvd@chromium.org</owner>
+  <owner>catan-team@chromium.org</owner>
+  <summary>
+    The amount of available physical memory on the system as reported by
+    base::SysInfo::AmountOfAvailablePhysicalMemory().
+
+    Recorded every 2 minutes.
+  </summary>
+</histogram>
+
+<histogram name="Memory.Experimental.AvailableMemoryPercent" units="%"
+    expires_after="2023-09-22">
+  <owner>anthonyvd@chromium.org</owner>
+  <owner>catan-team@chromium.org</owner>
+  <summary>
+    The percentage of physical memory on the system considered
+    &quot;available&quot; by base::SysInfo::AmountOfAvailablePhysicalMemory()
+    and base::SysInfo::AmountOfPhysicalMemory().
+
+    Recorded every 2 minutes.
+  </summary>
+</histogram>
+
 <histogram base="true" name="Memory.Experimental.Browser2" units="MB"
     expires_after="2024-01-10">
 <!-- Name completed by histogram_suffixes name="ProcessMemoryAllocator2" -->