Merge branch 'main' into DRTVWR-582-maint-U

1 files changed, 548 insertions, 0 deletions

diff --git a/indra/newview/llperfstats.cpp b/indra/newview/llperfstats.cpp
new file mode 100644
index 0000000000..7ff363c3c1
--- /dev/null
+++ b/indra/newview/llperfstats.cpp
@@ -0,0 +1,548 @@
+/** 
+* @file llperfstats.cpp
+* @brief Statistics collection to support autotune and perf flaoter.
+*
+* $LicenseInfo:firstyear=2022&license=viewerlgpl$
+* Second Life Viewer Source Code
+* Copyright (C) 2022, Linden Research, Inc.
+* 
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public
+* License as published by the Free Software Foundation;
+* version 2.1 of the License only.
+* 
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+* Lesser General Public License for more details.
+* 
+* You should have received a copy of the GNU Lesser General Public
+* License along with this library; if not, write to the Free Software
+* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+* 
+* Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+* $/LicenseInfo$
+*/
+
+#include "llviewerprecompiledheaders.h"
+#include "llperfstats.h"
+#include "llcontrol.h"
+#include "pipeline.h"
+#include "llagentcamera.h"
+#include "llviewerwindow.h"
+#include "llvoavatar.h"
+#include "llwindow.h"
+#include "llworld.h"
+#include <llthread.h>
+
+extern LLControlGroup gSavedSettings;
+
+namespace LLPerfStats
+{
+    std::atomic<int64_t> tunedAvatars{0};
+    std::atomic<U64> renderAvatarMaxART_ns{(U64)(ART_UNLIMITED_NANOS)}; // highest render time we'll allow without culling features
+    bool belowTargetFPS{false};
+    U32 lastGlobalPrefChange{0}; 
+    U32 lastSleepedFrame{0};
+    U64 meanFrameTime{0};
+    std::mutex bufferToggleLock{};
+
+    F64 cpu_hertz{0.0};
+    U32 vsync_max_fps{60};
+
+    Tunables tunables;
+
+    std::atomic<int> 	StatsRecorder::writeBuffer{0};
+    bool 	            StatsRecorder::collectionEnabled{true};
+    LLUUID              StatsRecorder::focusAv{LLUUID::null};
+    bool                StatsRecorder::autotuneInit{false};
+	std::array<StatsRecorder::StatsTypeMatrix,2>  StatsRecorder::statsDoubleBuffer{ {} };
+    std::array<StatsRecorder::StatsSummaryArray,2> StatsRecorder::max{ {} };
+    std::array<StatsRecorder::StatsSummaryArray,2> StatsRecorder::sum{ {} };
+
+    void Tunables::applyUpdates()
+    {
+        assert_main_thread();
+        // these following variables are proxies for pipeline statics we do not need a two way update (no llviewercontrol handler)
+        if( tuningFlag & NonImpostors ){ gSavedSettings.setU32("IndirectMaxNonImpostors", nonImpostors); };
+        if( tuningFlag & ReflectionDetail ){ gSavedSettings.setS32("RenderReflectionDetail", reflectionDetail); };
+        if( tuningFlag & FarClip ){ gSavedSettings.setF32("RenderFarClip", farClip); };
+        if( tuningFlag & UserMinDrawDistance ){ gSavedSettings.setF32("AutoTuneRenderFarClipMin", userMinDrawDistance); };
+        if( tuningFlag & UserTargetDrawDistance ){ gSavedSettings.setF32("AutoTuneRenderFarClipTarget", userTargetDrawDistance); };
+        if( tuningFlag & UserImpostorDistance ){ gSavedSettings.setF32("AutoTuneImpostorFarAwayDistance", userImpostorDistance); };
+        if( tuningFlag & UserImpostorDistanceTuningEnabled ){ gSavedSettings.setBOOL("AutoTuneImpostorByDistEnabled", userImpostorDistanceTuningEnabled); };
+        if( tuningFlag & UserFPSTuningStrategy ){ gSavedSettings.setU32("TuningFPSStrategy", userFPSTuningStrategy); };
+        if( tuningFlag & UserAutoTuneEnabled ){ gSavedSettings.setBOOL("AutoTuneFPS", userAutoTuneEnabled); };
+        if( tuningFlag & UserAutoTuneLock ){ gSavedSettings.setBOOL("AutoTuneLock", userAutoTuneLock); };
+        if( tuningFlag & UserTargetFPS ){ gSavedSettings.setU32("TargetFPS", userTargetFPS); };
+        if( tuningFlag & UserTargetReflections ){ gSavedSettings.setS32("UserTargetReflections", userTargetReflections); };
+        // Note: The Max ART slider is logarithmic and thus we have an intermediate proxy value
+        if( tuningFlag & UserARTCutoff ){ gSavedSettings.setF32("RenderAvatarMaxART", userARTCutoffSliderValue); };
+        resetChanges();
+    }
+
+    void Tunables::updateRenderCostLimitFromSettings()
+    {
+        assert_main_thread();
+        const auto newval = gSavedSettings.getF32("RenderAvatarMaxART");
+        if(newval < log10(LLPerfStats::ART_UNLIMITED_NANOS/1000))
+        {
+            LLPerfStats::renderAvatarMaxART_ns = pow(10,newval)*1000;
+        }
+        else
+        {
+            LLPerfStats::renderAvatarMaxART_ns = 0;
+        }
+    }
+
+    // static 
+    void Tunables::updateSettingsFromRenderCostLimit()
+    {
+        if( userARTCutoffSliderValue != log10( ( (F32)LLPerfStats::renderAvatarMaxART_ns )/1000 ) )
+        {
+            if( LLPerfStats::renderAvatarMaxART_ns != 0 )
+            {
+                updateUserARTCutoffSlider(log10( ( (F32)LLPerfStats::renderAvatarMaxART_ns )/1000 ) );
+            }
+            else
+            {
+                updateUserARTCutoffSlider(log10( (F32)LLPerfStats::ART_UNLIMITED_NANOS/1000 ) );
+            }
+        }        
+    }
+
+    void Tunables::initialiseFromSettings()
+    {
+        assert_main_thread();
+        // the following variables are two way and have "push" in llviewercontrol 
+        LLPerfStats::tunables.userMinDrawDistance = gSavedSettings.getF32("AutoTuneRenderFarClipMin");
+        LLPerfStats::tunables.userTargetDrawDistance = gSavedSettings.getF32("AutoTuneRenderFarClipTarget");
+        LLPerfStats::tunables.userImpostorDistance = gSavedSettings.getF32("AutoTuneImpostorFarAwayDistance");
+        LLPerfStats::tunables.userImpostorDistanceTuningEnabled = gSavedSettings.getBOOL("AutoTuneImpostorByDistEnabled");
+        LLPerfStats::tunables.userFPSTuningStrategy = gSavedSettings.getU32("TuningFPSStrategy");
+        LLPerfStats::tunables.userTargetFPS = gSavedSettings.getU32("TargetFPS");
+        LLPerfStats::tunables.vsyncEnabled = gSavedSettings.getBOOL("RenderVSyncEnable");
+        LLPerfStats::tunables.userTargetReflections = gSavedSettings.getS32("UserTargetReflections");
+
+        LLPerfStats::tunables.userAutoTuneLock = gSavedSettings.getBOOL("AutoTuneLock") && gSavedSettings.getU32("KeepAutoTuneLock");
+
+        if(gSavedSettings.getBOOL("AutoTuneLock") && !gSavedSettings.getU32("KeepAutoTuneLock"))
+        {
+            gSavedSettings.setBOOL("AutoTuneLock", FALSE);
+        }
+
+        LLPerfStats::tunables.userAutoTuneEnabled = LLPerfStats::tunables.userAutoTuneLock;
+
+        if (LLPerfStats::tunables.userAutoTuneEnabled && !gSavedSettings.getBOOL("AutoTuneFPS"))
+        {
+            gSavedSettings.setBOOL("AutoTuneFPS", TRUE);
+        }
+
+        // Note: The Max ART slider is logarithmic and thus we have an intermediate proxy value
+        updateRenderCostLimitFromSettings();
+        resetChanges();
+    }
+
+    StatsRecorder::StatsRecorder():q(1024*16),t(&StatsRecorder::run)
+    {
+        // create a queue
+        // create a thread to consume from the queue
+        tunables.initialiseFromSettings();
+        LLPerfStats::cpu_hertz = (F64)LLTrace::BlockTimer::countsPerSecond();
+        LLPerfStats::vsync_max_fps = gViewerWindow->getWindow()->getRefreshRate();
+        t.detach();
+    }
+
+    // static
+    void StatsRecorder::toggleBuffer()
+    {
+        LL_PROFILE_ZONE_SCOPED_CATEGORY_STATS;
+        using ST = StatType_t;
+
+        bool unreliable{false};
+        LLPerfStats::StatsRecorder::getSceneStat(LLPerfStats::StatType_t::RENDER_FRAME);
+        auto& sceneStats = statsDoubleBuffer[writeBuffer][static_cast<size_t>(ObjType_t::OT_GENERAL)][LLUUID::null];
+        auto& lastStats = statsDoubleBuffer[writeBuffer ^ 1][static_cast<size_t>(ObjType_t::OT_GENERAL)][LLUUID::null];
+
+        static constexpr std::initializer_list<StatType_t> sceneStatsToAvg = {
+            StatType_t::RENDER_FRAME, 
+            StatType_t::RENDER_DISPLAY, 
+            StatType_t::RENDER_HUDS,
+            StatType_t::RENDER_UI,
+            StatType_t::RENDER_SWAP,
+            // RENDER_LFS,
+            // RENDER_MESHREPO,
+            StatType_t::RENDER_IDLE };
+
+        static constexpr std::initializer_list<StatType_t> avatarStatsToAvg = {
+            StatType_t::RENDER_GEOMETRY, 
+            StatType_t::RENDER_SHADOWS, 
+            StatType_t::RENDER_COMBINED,
+            StatType_t::RENDER_IDLE };
+
+
+        if( /*sceneStats[static_cast<size_t>(StatType_t::RENDER_FPSLIMIT)] != 0 ||*/ sceneStats[static_cast<size_t>(StatType_t::RENDER_SLEEP)] != 0 )
+        {
+            unreliable = true;
+            //lastStats[static_cast<size_t>(StatType_t::RENDER_FPSLIMIT)] = sceneStats[static_cast<size_t>(StatType_t::RENDER_FPSLIMIT)];
+            lastStats[static_cast<size_t>(StatType_t::RENDER_SLEEP)] = sceneStats[static_cast<size_t>(StatType_t::RENDER_SLEEP)];
+            lastStats[static_cast<size_t>(StatType_t::RENDER_FRAME)] = sceneStats[static_cast<size_t>(StatType_t::RENDER_FRAME)]; //  bring over the total frame render time to deal with region crossing overlap issues
+        }
+
+        if(!unreliable)
+        {
+            // only use these stats when things are reliable. 
+
+            for(auto & statEntry : sceneStatsToAvg)
+            {
+                auto avg = lastStats[static_cast<size_t>(statEntry)];
+                auto val = sceneStats[static_cast<size_t>(statEntry)];
+                sceneStats[static_cast<size_t>(statEntry)] = avg + (val / SMOOTHING_PERIODS) - (avg / SMOOTHING_PERIODS);
+                // LL_INFOS("scenestats") << "Scenestat: " << static_cast<size_t>(statEntry) << " before=" << avg << " new=" << val << " newavg=" << statsDoubleBuffer[writeBuffer][static_cast<size_t>(ObjType_t::OT_GENERAL)][LLUUID::null][static_cast<size_t>(statEntry)] << LL_ENDL;
+            }
+        }
+// Allow attachment times etc to update even when FPS limited or sleeping.
+        auto& statsMap = statsDoubleBuffer[writeBuffer][static_cast<size_t>(ObjType_t::OT_ATTACHMENT)];
+        for(auto& stat_entry : statsMap)
+        {
+            auto val = stat_entry.second[static_cast<size_t>(ST::RENDER_COMBINED)];
+            if(val > SMOOTHING_PERIODS){
+                auto avg = statsDoubleBuffer[writeBuffer ^ 1][static_cast<size_t>(ObjType_t::OT_ATTACHMENT)][stat_entry.first][static_cast<size_t>(ST::RENDER_COMBINED)];
+                stat_entry.second[static_cast<size_t>(ST::RENDER_COMBINED)] = avg + (val / SMOOTHING_PERIODS) - (avg / SMOOTHING_PERIODS);
+            }
+        }
+
+
+        auto& statsMapAv = statsDoubleBuffer[writeBuffer][static_cast<size_t>(ObjType_t::OT_AVATAR)];
+        for(auto& stat_entry : statsMapAv)
+        {
+            for(auto& stat : avatarStatsToAvg)
+            {
+                auto val = stat_entry.second[static_cast<size_t>(stat)];
+                if(val > SMOOTHING_PERIODS)
+                {
+                    auto avg = statsDoubleBuffer[writeBuffer ^ 1][static_cast<size_t>(ObjType_t::OT_AVATAR)][stat_entry.first][static_cast<size_t>(stat)];
+                    stat_entry.second[static_cast<size_t>(stat)] = avg + (val / SMOOTHING_PERIODS) - (avg / SMOOTHING_PERIODS);
+                }
+            }
+        }
+
+        // swap the buffers
+        if(enabled())
+        {
+            std::lock_guard<std::mutex> lock{bufferToggleLock};
+            writeBuffer ^= 1;
+        }; // note we are relying on atomic updates here. The risk is low and would cause minor errors in the stats display. 
+
+        // clean the write maps in all cases.
+        auto& statsTypeMatrix = statsDoubleBuffer[writeBuffer];
+        for(auto& statsMapByType : statsTypeMatrix)
+        {
+            LL_PROFILE_ZONE_NAMED_CATEGORY_STATS("Clear stats maps");
+            for(auto& stat_entry : statsMapByType)
+            {
+                std::fill_n(stat_entry.second.begin() ,static_cast<size_t>(ST::STATS_COUNT),0);
+            }
+            statsMapByType.clear();
+        }
+        for(int i=0; i< static_cast<size_t>(ObjType_t::OT_COUNT); i++)
+        {
+            LL_PROFILE_ZONE_NAMED_CATEGORY_STATS("clear max/sum");
+            max[writeBuffer][i].fill(0);
+            sum[writeBuffer][i].fill(0);
+        }
+
+        // and now adjust the proxy vars so that the main thread can adjust the visuals.
+        if(autotuneInit && tunables.userAutoTuneEnabled)
+        {
+            updateAvatarParams();
+        }
+    }
+
+    // clear buffers when we change region or need a hard reset.
+    // static 
+    void StatsRecorder::clearStatsBuffers()
+    {
+        LL_PROFILE_ZONE_SCOPED_CATEGORY_STATS;
+        using ST = StatType_t;
+
+        auto& statsTypeMatrix = statsDoubleBuffer[writeBuffer];
+        for(auto& statsMap : statsTypeMatrix)
+        {
+            LL_PROFILE_ZONE_NAMED_CATEGORY_STATS("Clear stats maps");
+            for(auto& stat_entry : statsMap)
+            {
+                std::fill_n(stat_entry.second.begin() ,static_cast<size_t>(ST::STATS_COUNT),0);
+            }
+            statsMap.clear();
+        }
+        for(int i=0; i< static_cast<size_t>(ObjType_t::OT_COUNT); i++)
+        {
+            LL_PROFILE_ZONE_NAMED_CATEGORY_STATS("clear max/sum");
+            max[writeBuffer][i].fill(0);
+            sum[writeBuffer][i].fill(0);
+        }
+        // swap the clean buffers in
+        if(enabled())
+        {
+            std::lock_guard<std::mutex> lock{bufferToggleLock};
+            writeBuffer ^= 1;
+        }; 
+        // repeat before we start processing new stuff
+        for(auto& statsMap : statsTypeMatrix)
+        {
+            LL_PROFILE_ZONE_NAMED_CATEGORY_STATS("Clear stats maps");
+            for(auto& stat_entry : statsMap)
+            {
+                std::fill_n(stat_entry.second.begin() ,static_cast<size_t>(ST::STATS_COUNT),0);
+            }
+            statsMap.clear();
+        }
+        for(int i=0; i< static_cast<size_t>(ObjType_t::OT_COUNT); i++)
+        {
+            LL_PROFILE_ZONE_NAMED_CATEGORY_STATS("clear max/sum");
+            max[writeBuffer][i].fill(0);
+            sum[writeBuffer][i].fill(0);
+        }
+    }
+
+    //static
+    int StatsRecorder::countNearbyAvatars(S32 distance)
+    {
+        const auto our_pos = gAgentCamera.getCameraPositionGlobal();
+
+       	std::vector<LLVector3d> positions;
+	    uuid_vec_t avatar_ids;
+        LLWorld::getInstance()->getAvatars(&avatar_ids, &positions, our_pos, distance);
+        return positions.size();
+	}
+
+    const U32 NUM_PERIODS = 50;
+    void StatsRecorder::updateMeanFrameTime(U64 cur_frame_time_raw)
+    {
+        static std::deque<U64> frame_time_deque;
+        frame_time_deque.push_front(cur_frame_time_raw);
+        if (frame_time_deque.size() > NUM_PERIODS)
+        {
+            frame_time_deque.pop_back();
+        }
+        
+        std::vector<U64> buf(frame_time_deque.begin(), frame_time_deque.end());
+        std::sort(buf.begin(), buf.end());
+
+        LLPerfStats::meanFrameTime = (buf.size() % 2 == 0) ? (buf[buf.size() / 2 - 1] + buf[buf.size() / 2]) / 2 : buf[buf.size() / 2];
+    }
+    U64 StatsRecorder::getMeanTotalFrameTime()
+    {
+        return LLPerfStats::meanFrameTime;
+    }
+
+    // static
+    void StatsRecorder::updateAvatarParams()
+    {
+        if(tunables.autoTuneTimeout)
+        {
+            LLPerfStats::lastSleepedFrame = gFrameCount;
+            tunables.autoTuneTimeout = false;
+            return;
+        }
+        // sleep time is basically forced sleep when window out of focus
+        auto tot_sleep_time_raw = LLPerfStats::StatsRecorder::getSceneStat(LLPerfStats::StatType_t::RENDER_SLEEP);
+        // similar to sleep time, induced by FPS limit
+        //auto tot_limit_time_raw = LLPerfStats::StatsRecorder::getSceneStat(LLPerfStats::StatType_t::RENDER_FPSLIMIT);
+
+
+        // the time spent this frame on the "doFrame" call. Treated as "tot time for frame"
+        auto tot_frame_time_raw = LLPerfStats::StatsRecorder::getSceneStat(LLPerfStats::StatType_t::RENDER_FRAME);
+
+        if( tot_sleep_time_raw != 0 )
+        {
+            // Note: we do not average sleep 
+            // if at some point we need to, the averaging will need to take this into account or 
+            // we forever think we're in the background due to residuals.
+            LL_DEBUGS() << "No tuning when not in focus" << LL_ENDL;
+            LLPerfStats::lastSleepedFrame = gFrameCount;
+            return;
+        }
+
+        U32 target_fps = tunables.vsyncEnabled ? std::min(LLPerfStats::vsync_max_fps, tunables.userTargetFPS) : tunables.userTargetFPS;
+
+        if(LLPerfStats::lastSleepedFrame != 0)
+        {
+            // wait a short time after viewer regains focus
+            if((gFrameCount - LLPerfStats::lastSleepedFrame) > target_fps * 5)
+            {
+                LLPerfStats::lastSleepedFrame = 0;
+            }
+            else
+            {
+                return;
+            }
+        }
+        updateMeanFrameTime(tot_frame_time_raw);
+
+        if(tunables.userImpostorDistanceTuningEnabled)
+        {
+            // if we have less than the user's "max Non-Impostors" avatars within the desired range then adjust the limit.
+            // also adjusts back up again for nearby crowds.
+            auto count = countNearbyAvatars(std::min(LLPipeline::RenderFarClip, tunables.userImpostorDistance));
+            if( count != tunables.nonImpostors )
+            {
+                tunables.updateNonImposters( (count < LLVOAvatar::NON_IMPOSTORS_MAX_SLIDER)?count : LLVOAvatar::NON_IMPOSTORS_MAX_SLIDER );
+                LL_DEBUGS("AutoTune") << "There are " << count << "avatars within " << std::min(LLPipeline::RenderFarClip, tunables.userImpostorDistance) << "m of the camera" << LL_ENDL;
+            }
+        }
+
+        auto av_render_max_raw = LLPerfStats::StatsRecorder::getMax(ObjType_t::OT_AVATAR, LLPerfStats::StatType_t::RENDER_COMBINED);
+        // Is our target frame time lower than current? If so we need to take action to reduce draw overheads.
+        // cumulative avatar time (includes idle processing, attachments and base av)
+        auto tot_avatar_time_raw = LLPerfStats::StatsRecorder::getSum(ObjType_t::OT_AVATAR, LLPerfStats::StatType_t::RENDER_COMBINED);
+
+        // The frametime budget we have based on the target FPS selected
+        auto target_frame_time_raw = (U64)llround(LLPerfStats::cpu_hertz / (target_fps == 0 ? 1 : target_fps));
+        // LL_INFOS() << "Effective FPS(raw):" << tot_frame_time_raw << " Target:" << target_frame_time_raw << LL_ENDL;
+        auto inferredFPS{1000/(U32)std::max(raw_to_ms(tot_frame_time_raw),1.0)};
+        U32 settingsChangeFrequency{inferredFPS > 50?inferredFPS:50};
+        /*if( tot_limit_time_raw != 0)
+        {
+            // This could be problematic.
+            tot_frame_time_raw -= tot_limit_time_raw;
+        }*/
+        
+        F64 time_buf = target_frame_time_raw * 0.1;
+
+        // 1) Is the target frame time lower than current?
+        if ((target_frame_time_raw + time_buf) <= tot_frame_time_raw)
+        {
+            if (target_frame_time_raw - time_buf >= getMeanTotalFrameTime())
+            {
+                belowTargetFPS = false;
+                LLPerfStats::lastGlobalPrefChange = gFrameCount;
+                return;
+            }
+
+            if(belowTargetFPS == false)
+            {
+                // this is the first frame under. hold fire to add a little hysteresis
+                belowTargetFPS = true;
+                LLPerfStats::lastGlobalPrefChange = gFrameCount;
+            }
+            // if so we've got work to do
+
+            // how much of the frame was spent on non avatar related work?
+            U64 non_avatar_time_raw = tot_frame_time_raw - tot_avatar_time_raw;
+
+            // If the target frame time < scene time (estimated as non_avatar time)
+            U64 target_avatar_time_raw;
+            if(target_frame_time_raw < non_avatar_time_raw)
+            {
+                // we cannnot do this by avatar adjustment alone.
+                if((gFrameCount - LLPerfStats::lastGlobalPrefChange) > settingsChangeFrequency) // give  changes a short time to take effect.
+                {
+                    if(tunables.userFPSTuningStrategy != TUNE_AVATARS_ONLY)
+                    {
+                        // 1 - hack the water to opaque. all non opaque have a significant hit, this is a big boost for (arguably) a minor visual hit.
+                        // the other reflection options make comparatively little change and if this overshoots we'll be stepping back up later
+                        if(LLPipeline::RenderReflectionDetail != -2)
+                        {
+                            LLPerfStats::tunables.updateReflectionDetail(-2);
+                            LLPerfStats::lastGlobalPrefChange = gFrameCount;
+                            return;
+                        }
+                        else // deliberately "else" here so we only do one of these in any given frame
+                        {
+                            // step down the DD by 10m per update
+                            auto new_dd = (LLPipeline::RenderFarClip - DD_STEP > tunables.userMinDrawDistance)?(LLPipeline::RenderFarClip - DD_STEP) : tunables.userMinDrawDistance;
+                            if(new_dd != LLPipeline::RenderFarClip)
+                            {
+                                LLPerfStats::tunables.updateFarClip( new_dd );
+                                LLPerfStats::lastGlobalPrefChange = gFrameCount;
+                                return;
+                            }
+                        }
+                    }
+                    // if we reach here, we've no more changes to make to tune scenery so we'll resort to agressive Avatar tuning
+                    // Note: moved from outside "if changefrequency elapsed" to stop fallthrough and allow scenery changes time to take effect.
+                    target_avatar_time_raw = 0;
+                }
+                else 
+                {
+                    // we made a settings change recently so let's give it time.
+                    return;
+                }
+            }
+            else
+            {
+                // set desired avatar budget.
+                target_avatar_time_raw =  target_frame_time_raw - non_avatar_time_raw;
+            }
+
+            if ((target_avatar_time_raw < tot_avatar_time_raw) && (tunables.userFPSTuningStrategy != TUNE_SCENE_ONLY))
+            {
+                // we need to spend less time drawing avatars to meet our budget
+                auto new_render_limit_ns {LLPerfStats::raw_to_ns(av_render_max_raw)};
+                // max render this frame may be higher than the last (cos new entrants and jitter) so make sure we are heading in the right direction
+                if( new_render_limit_ns > renderAvatarMaxART_ns )
+                {
+                    new_render_limit_ns = renderAvatarMaxART_ns;
+                }
+                new_render_limit_ns -= LLPerfStats::ART_MIN_ADJUST_DOWN_NANOS;
+
+                // bounce at the bottom to prevent "no limit" 
+                new_render_limit_ns = std::max((U64)new_render_limit_ns, (U64)LLPerfStats::ART_MINIMUM_NANOS);
+
+                // assign the new value
+                if(renderAvatarMaxART_ns != new_render_limit_ns)
+                {
+                    renderAvatarMaxART_ns = new_render_limit_ns;
+                    tunables.updateSettingsFromRenderCostLimit();
+                }
+                // LL_DEBUGS() << "AUTO_TUNE: avatar_budget adjusted to:" << new_render_limit_ns << LL_ENDL;
+            }
+            // LL_DEBUGS() << "AUTO_TUNE: Target frame time:"<< LLPerfStats::raw_to_us(target_frame_time_raw) << "usecs (non_avatar is " << LLPerfStats::raw_to_us(non_avatar_time_raw) << "usecs) Max cost limited=" << renderAvatarMaxART_ns << LL_ENDL;
+        }
+        else if(( LLPerfStats::raw_to_ns(target_frame_time_raw) > (LLPerfStats::raw_to_ns(tot_frame_time_raw) + renderAvatarMaxART_ns) ) ||
+                 (tunables.vsyncEnabled && (target_fps == LLPerfStats::vsync_max_fps) && (target_frame_time_raw > getMeanTotalFrameTime())))
+        {
+            if(belowTargetFPS == true)
+            {
+                // we reached target, force a pause
+                lastGlobalPrefChange = gFrameCount;
+                belowTargetFPS = false;
+            }
+
+            // once we're over the FPS target we slow down further
+            if((gFrameCount - lastGlobalPrefChange) > settingsChangeFrequency*3)
+            {
+                if(!tunables.userAutoTuneLock)
+                {
+                    // we've reached the target and stayed long enough to consider stable.
+                    // turn off if we are not locked.
+                    tunables.updateUserAutoTuneEnabled(false);
+                }
+                if(renderAvatarMaxART_ns != 0 && LLPerfStats::tunedAvatars > 0 && (tunables.userFPSTuningStrategy != TUNE_SCENE_ONLY) )
+                {
+                    // if we have more time to spare let's shift up little in the hope we'll restore an avatar.
+                    U64 up_step = LLPerfStats::tunedAvatars > 2 ? LLPerfStats::ART_MIN_ADJUST_UP_NANOS : LLPerfStats::ART_MIN_ADJUST_UP_NANOS * 2;
+                    renderAvatarMaxART_ns += up_step;
+                    tunables.updateSettingsFromRenderCostLimit();
+                    return;
+                }
+                if(tunables.userFPSTuningStrategy != TUNE_AVATARS_ONLY)
+                {
+                    if( LLPipeline::RenderFarClip < tunables.userTargetDrawDistance ) 
+                    {
+                        LLPerfStats::tunables.updateFarClip( std::min(LLPipeline::RenderFarClip + DD_STEP, tunables.userTargetDrawDistance) );
+                        LLPerfStats::lastGlobalPrefChange = gFrameCount;
+                        return;
+                    }
+                    if( (tot_frame_time_raw * 1.5) < target_frame_time_raw )
+                    {
+                        // if everything else is "max" and we have >50% headroom let's knock the water quality up a notch at a time.
+                        LLPerfStats::tunables.updateReflectionDetail( std::min(LLPipeline::RenderReflectionDetail + 1, tunables.userTargetReflections) );
+                    }
+                }
+            }
+        }
+   }
+}