From 024da37b8bbdf2daf7d7fa40b12229ee74b43df4 Mon Sep 17 00:00:00 2001
From: "Jonathan \"Geenz\" Goodman" <geenz@lindenlab.com>
Date: Wed, 13 Aug 2025 13:48:55 -0400
Subject: Add support for Normalized Frametime Variation (NVFT) (#4395)

* Add support for Normalized Frametime Variation (NVFT)

* Add normalized period jitter
---
 indra/newview/llviewerstats.cpp                    | 30 ++++++++++++++++++++++
 indra/newview/llviewerstats.h                      |  9 +++++++
 .../newview/skins/default/xui/en/floater_stats.xml |  8 ++++++
 3 files changed, 47 insertions(+)

(limited to 'indra')

diff --git a/indra/newview/llviewerstats.cpp b/indra/newview/llviewerstats.cpp
index a4f308bbf9..d39d466205 100644
--- a/indra/newview/llviewerstats.cpp
+++ b/indra/newview/llviewerstats.cpp
@@ -234,6 +234,8 @@ LLTrace::SampleStatHandle<U32> FRAMETIME_JITTER_EVENTS("frametimeevents", "Numbe
                                 FRAMETIME_JITTER_EVENTS_LAST_MINUTE("frametimeeventslastmin", "Number of frametime events in the last minute.");
 
 LLTrace::SampleStatHandle<F64> NOTRMALIZED_FRAMETIME_JITTER_SESSION("normalizedframetimejitter", "Normalized frametime jitter over the session.");
+LLTrace::SampleStatHandle<F64> NFTV("nftv", "Normalized frametime variation.");
+LLTrace::SampleStatHandle<F64> NORMALIZED_FRAMTIME_JITTER_PERIOD("normalizedframetimejitterperiod", "Normalized frametime jitter over the last 5 seconds.");
 
 LLTrace::EventStatHandle<LLUnit<F64, LLUnits::Meters> > AGENT_POSITION_SNAP("agentpositionsnap", "agent position corrections");
 
@@ -322,6 +324,8 @@ void LLViewerStats::updateFrameStats(const F64Seconds time_diff)
         sample(LLStatViewer::FRAMETIME_JITTER_CUMULATIVE, mTotalFrametimeJitter);
         sample(LLStatViewer::NOTRMALIZED_FRAMETIME_JITTER_SESSION, mTotalFrametimeJitter / mTotalTime);
 
+        mLastNoramlizedSessionJitter = mTotalFrametimeJitter / mTotalTime;
+
         static LLCachedControl<F32> frameTimeEventThreshold(gSavedSettings, "StatsFrametimeEventThreshold", 0.1f);
 
         if (time_diff - mLastTimeDiff > mLastTimeDiff * frameTimeEventThreshold())
@@ -360,6 +364,27 @@ void LLViewerStats::updateFrameStats(const F64Seconds time_diff)
             sample(LLStatViewer::FRAMETIME_JITTER_99TH, ninety_ninth_percentile);
             sample(LLStatViewer::FRAMETIME_JITTER_95TH, ninety_fifth_percentile);
 
+            F64 averageFrameTime = 0;
+            for (const auto& frame_time : mFrameTimes)
+            {
+                averageFrameTime += frame_time.value();
+            }
+            averageFrameTime /= mFrameTimes.size();
+
+            sample(LLStatViewer::NFTV, frame_time_stddev / averageFrameTime);
+            mLastNormalizedFrametimeVariance = frame_time_stddev / averageFrameTime;
+
+            // Add up all of the jitter values.
+            F64 totalJitter = 0;
+            for (const auto& frame_jitter : mFrameTimesJitter)
+            {
+                totalJitter += frame_jitter.value();
+            }
+
+            mLastNormalizedPeriodJitter = totalJitter / mLastFrameTimeSample;
+
+            sample(LLStatViewer::NORMALIZED_FRAMTIME_JITTER_PERIOD, mLastNormalizedPeriodJitter);
+
             mFrameTimes.clear();
             mFrameTimesJitter.clear();
             mLastFrameTimeSample = F64Seconds(0);
@@ -648,6 +673,11 @@ void send_viewer_stats(bool include_preferences)
 
     // send fps only for time app spends in foreground
     agent["fps"] = (F32)gForegroundFrameCount / gForegroundTime.getElapsedTimeF32();
+
+    agent["normalized_session_jitter"] = LLViewerStats::instance().getLastNormalizedSessionJitter();
+    agent["normalized_frametime_variance"] = LLViewerStats::instance().getLastNormalizedFrametimeVariance();
+    agent["normalized_period_jitter"]      = LLViewerStats::instance().getLastNormalizedPeriodJitter();
+
     agent["version"] = LLVersionInfo::instance().getChannelAndVersion();
     std::string language = LLUI::getLanguage();
     agent["language"] = language;
diff --git a/indra/newview/llviewerstats.h b/indra/newview/llviewerstats.h
index 63fb7d4a17..011269d7ee 100644
--- a/indra/newview/llviewerstats.h
+++ b/indra/newview/llviewerstats.h
@@ -271,6 +271,10 @@ public:
     LLTrace::Recording& getRecording() { return mRecording; }
     const LLTrace::Recording& getRecording() const { return mRecording; }
 
+    F64 getLastNormalizedSessionJitter() const { return mLastNoramlizedSessionJitter; }
+    F64 getLastNormalizedFrametimeVariance() const { return mLastNormalizedFrametimeVariance; }
+    F64 getLastNormalizedPeriodJitter() const { return mLastNormalizedPeriodJitter; }
+
 private:
     LLTrace::Recording              mRecording;
 
@@ -286,6 +290,11 @@ private:
     F64Seconds              mTimeSinceLastEventSample;
     std::vector<F64Seconds>      mFrameTimes;          // used for frame time stats
     std::vector<F64Seconds> mFrameTimesJitter;    // used for frame time jitter stats
+
+    F64 mLastNoramlizedSessionJitter; // used for frame time jitter stats
+    F64 mLastNormalizedFrametimeVariance; // Used when submitting jitter stats
+    F64 mLastNormalizedPeriodJitter;
+
 };
 
 static const F32 SEND_STATS_PERIOD = 300.0f;
diff --git a/indra/newview/skins/default/xui/en/floater_stats.xml b/indra/newview/skins/default/xui/en/floater_stats.xml
index f2309eb817..1600c422c3 100644
--- a/indra/newview/skins/default/xui/en/floater_stats.xml
+++ b/indra/newview/skins/default/xui/en/floater_stats.xml
@@ -58,6 +58,14 @@
                     label="normalized sess. jitter"
                     decimal_digits="4"
                     stat="normalizedframetimejitter"/>
+          <stat_bar name="normalized_period_jitter"
+                    label="normalized period jitter"
+                    decimal_digits="4"
+                    stat="normalizedframetimejitterperiod"/>
+          <stat_bar name="normalized_frametime_variation"
+                    label="normalized frametime variation"
+                    decimal_digits="4"
+                    stat="nftv"/>
           <stat_bar name="frame_events_per_minute"
                     label="frame events/minute"
                     decimal_digits="2"
-- 
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