Record reasons of OOM intervention failures to UMA

We observe that the intervention does not have any effect on population.
Add metrics to see why it fails.

BUG=843419

Change-Id: I1e7443a749331135dbbad9c51ff79ba9d1975db7
Reviewed-on: https://chromium-review.googlesource.com/1083594
Commit-Queue: Siddhartha S <ssid@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564330}

chrome/browser/android/oom_intervention/oom_intervention_config.cc

@@ -6,6 +6,7 @@
 
 #include "base/feature_list.h"
 #include "base/metrics/field_trial_params.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/sys_info.h"
 #include "chrome/common/chrome_features.h"
@@ -95,6 +96,15 @@ bool GetSwapFreeThreshold(uint64_t* threshold) {
   return true;
 }
 
+// These values are persisted to logs. Entries should not be renumbered and
+// numeric values should never be reused.
+enum class OomInterventionBrowserMonitorStatus {
+  kEnabledWithValidConfig = 0,
+  kDisabledWithInvalidParam = 1,
+  kDisabledWithNoSwap = 2,
+  kMaxValue = kDisabledWithNoSwap
+};
+
 }  // namespace
 
 OomInterventionConfig::OomInterventionConfig()
@@ -114,10 +124,17 @@ OomInterventionConfig::OomInterventionConfig()
 
   // Enable intervention only if at least one threshold is set for detection
   // in each process.
-  if (!GetSwapFreeThreshold(&swapfree_threshold_) ||
-      !GetRendererMemoryThresholds(&renderer_detection_args_)) {
+  OomInterventionBrowserMonitorStatus status =
+      OomInterventionBrowserMonitorStatus::kEnabledWithValidConfig;
+  if (!GetSwapFreeThreshold(&swapfree_threshold_)) {
+    is_intervention_enabled_ = false;
+    status = OomInterventionBrowserMonitorStatus::kDisabledWithNoSwap;
+  } else if (!GetRendererMemoryThresholds(&renderer_detection_args_)) {
     is_intervention_enabled_ = false;
+    status = OomInterventionBrowserMonitorStatus::kDisabledWithInvalidParam;
   }
+  UMA_HISTOGRAM_ENUMERATION(
+      "Memory.Experimental.OomIntervention.BrowserMonitorStatus", status);
 }
 
 // static

chrome/browser/android/oom_intervention/oom_intervention_tab_helper.cc

@@ -61,7 +61,7 @@ void RecordInterventionStateOnCrash(bool accepted) {
 
 // static
 bool OomInterventionTabHelper::IsEnabled() {
-  return NearOomMonitor::GetInstance() != nullptr;
+  return OomInterventionConfig::GetInstance()->is_intervention_enabled();
 }
 
 OomInterventionTabHelper::OomInterventionTabHelper(

third_party/blink/renderer/controller/oom_intervention_impl.cc

@@ -8,6 +8,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 
+#include "base/metrics/histogram_macros.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "third_party/blink/public/platform/platform.h"
 #include "third_party/blink/renderer/platform/bindings/v8_per_isolate_data.h"
@@ -79,6 +80,20 @@ uint64_t BlinkMemoryWorkloadCaculator() {
   return v8_size + blink_gc_size + partition_alloc_size;
 }
 
+// These values are persisted to logs. Entries should not be renumbered and
+// numeric values should never be reused.
+enum class RendererInterventionEnabledStatus {
+  kDetectionOnlyEnabled = 0,
+  kTriggerEnabled = 1,
+  kDisabledFailedMemoryMetricsFetch = 2,
+  kMaxValue = kDisabledFailedMemoryMetricsFetch
+};
+
+void RecordEnabledStatus(RendererInterventionEnabledStatus status) {
+  UMA_HISTOGRAM_ENUMERATION(
+      "Memory.Experimental.OomIntervention.RendererEnabledStatus", status);
+}
+
 }  // namespace
 
 // static
@@ -109,10 +124,15 @@ void OomInterventionImpl::StartDetection(
   if (!status_fd_.is_valid())
     status_fd_.reset(open("/proc/self/status", O_RDONLY));
   // Disable intervention if we cannot get memory details of current process.
-  // TODO(ssid): Add UMA here to make sure we don't stop disable intervention
-  // more often than expected.
-  if (!statm_fd_.is_valid() || !status_fd_.is_valid())
+  if (!statm_fd_.is_valid() || !status_fd_.is_valid()) {
+    RecordEnabledStatus(
+        RendererInterventionEnabledStatus::kDisabledFailedMemoryMetricsFetch);
     return;
+  }
+  RecordEnabledStatus(
+      trigger_intervention
+          ? RendererInterventionEnabledStatus::kTriggerEnabled
+          : RendererInterventionEnabledStatus::kDetectionOnlyEnabled);
 
   detection_args_ = std::move(detection_args);
   trigger_intervention_ = trigger_intervention;

tools/metrics/histograms/enums.xml

@@ -34438,6 +34438,18 @@ Called by update_net_trust_anchors.py.-->
   <int value="3" label="(non-invalidated) replies received"/>
 </enum>
 
+<enum name="OomInterventionBrowserMonitorStatus">
+  <int value="0" label="Enabled with a valid config"/>
+  <int value="1" label="Disabled since bad config param"/>
+  <int value="2" label="Disabled since device has no swap"/>
+</enum>
+
+<enum name="OomInterventionRendererStatus">
+  <int value="0" label="Detection only enabled on renderer"/>
+  <int value="1" label="Detection with trigger enabled on renderer"/>
+  <int value="2" label="Disabled since renderer cannot fetch memory total"/>
+</enum>
+
 <enum name="OomInterventionUserDecision">
   <int value="0" label="Declined"/>
   <int value="1" label="Accepted"/>

tools/metrics/histograms/histograms.xml

@@ -41890,6 +41890,16 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="Memory.Experimental.OomIntervention.BrowserMonitorStatus"
+    enum="OomInterventionBrowserMonitorStatus" expires_after="M70">
+  <owner>ssid@chromium.org</owner>
+  <summary>
+    Records the status of OOM intervention if the feature is turned on, with
+    various reasons for failure, in the browser process. Recorded once at
+    browser startup.
+  </summary>
+</histogram>
+
 <histogram name="Memory.Experimental.OomIntervention.InterventionStateOnCrash"
     enum="OomInterventionUserDecision">
   <owner>bashi@chromium.org</owner>
@@ -41938,6 +41948,16 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="Memory.Experimental.OomIntervention.RendererEnabledStatus"
+    enum="OomInterventionRendererStatus" expires_after="M70">
+  <owner>ssid@chromium.org</owner>
+  <summary>
+    Records the status of OOM intervention in renderer process if the feature is
+    turned on, with various reasons for failure. Recorded at each navigation or
+    reload.
+  </summary>
+</histogram>
+
 <histogram
     name="Memory.Experimental.OomIntervention.RendererGoneAfterDetectionTime"
     units="ms">