#4604 Restore system memory factor, but in LLMemory

8 files changed, 133 insertions, 13 deletions

diff --git a/indra/llcommon/llmemory.cpp b/indra/llcommon/llmemory.cpp
index 31424bfed3..4e44b9a56a 100644
--- a/indra/llcommon/llmemory.cpp
+++ b/indra/llcommon/llmemory.cpp
@@ -4,7 +4,7 @@
  *
  * $LicenseInfo:firstyear=2002&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2010, Linden Research, Inc.
+ * Copyright (C) 2026, 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
@@ -73,6 +73,12 @@ U32Kilobytes LLMemory::sAllocatedMemInKB(0);
 
 U32Kilobytes LLMemory::sAllocatedPageSizeInKB(0);
 
+LLFrameTimer LLMemory::sMemoryCheckTimer;
+F32 LLMemory::sSysMemoryFactor = 1.f;
+U32 LLMemory::sFactorLastFrameCount = 0;
+
+static const S32Megabytes MEM_LOW_THRESHOLD = S32Megabytes(256);
+
 
 static LLTrace::SampleStatHandle<F64Megabytes> sAllocatedMem("allocated_mem", "active memory in use by application");
 static LLTrace::SampleStatHandle<F64Megabytes> sVirtualMem("virtual_mem", "virtual memory assigned to application");
@@ -105,12 +111,13 @@ void LLMemory::updateMemoryInfo()
 {
     LL_PROFILE_ZONE_SCOPED;
 
+    sMemoryCheckTimer.reset();
     sMaxPhysicalMemInKB = gSysMemory.getPhysicalMemoryKB();
 
     LLMemoryInfo::updateAvailableMemory();
 
 #if LL_WINDOWS
-    // On windows getAvailableMemoryKB fills sAvailPhysicalMemInKB,
+    // On windows updateAvailableMemory fills sAvailPhysicalMemInKB,
     //sAllocatedMemInKB and sAllocatedPageSizeInKB
     sample(sVirtualMem, sAllocatedPageSizeInKB);
 
@@ -194,6 +201,86 @@ void LLMemory::logMemoryInfo(bool update)
     LL_INFOS() << llformat("Current max usable memory: %.2f MB", sMaxPhysicalMemInKB / 1024.0) << LL_ENDL;
 }
 
+void LLMemory::updateFreeSystemMemory()
+{
+    if (sMemoryCheckTimer.getElapsedTimeF32() >= 1.f) //once per second.
+    {
+        LLMemory::updateMemoryInfo(); // resets the timer
+    }
+}
+
+F32 LLMemory::getSystemMemoryBudgetFactor()
+{
+    // Only update once per frame
+    U32 current_frame = LLFrameTimer::getFrameCount();
+    if (sFactorLastFrameCount == current_frame)
+    {
+        return sSysMemoryFactor;
+    }
+    sFactorLastFrameCount = current_frame;
+
+    updateFreeSystemMemory();
+#if LL_WINDOWS
+    S32Megabytes free_sys_mem = getAvailableCommitMemMB();
+#else
+    S32Megabytes free_sys_mem = getAvailableMemKB();
+#endif
+    bool is_sys_low = free_sys_mem < MEM_LOW_THRESHOLD;
+    static bool was_low = false;
+
+    // sSysMemoryFactor affects draw distance
+    //
+    // We only decrement when more than 406MB is free, but increment
+    // when below 256MB free. This should provide a stable value
+    // in the 256-406MB range to avoid draw range fluctuations.
+    //
+    // Draw range reduction is a last resort, texture bias is supposed
+    // to free at least some memory before we get here.
+    // Note: textures were mostly moved to vram, we might want to
+    // detach texture bias from system memory.
+    if (is_sys_low)
+    {
+        // debt is a negative value since MIN_FREE_MAIN_MEMORY > free memory.
+        S32Megabytes sys_budget_debt = free_sys_mem - MEM_LOW_THRESHOLD;
+
+        // Leave some padding, otherwise we will crash out of memory before hitting factor 2.
+        const S32Megabytes PAD_BUFFER(32);
+        S32Megabytes budget_target = MEM_LOW_THRESHOLD - PAD_BUFFER;
+        if (!was_low)
+        {
+            // Result should range from 1 at 0 debt to 2 at -224 debt, 2.14 at -256MB
+            F32 new_factor = 1.f - (F32)sys_budget_debt.value() / (F32)budget_target.value();
+            sSysMemoryFactor = llmax(sSysMemoryFactor, new_factor);
+        }
+        else
+        {
+            // Slowly ramp up factor to free memory (increasing factor decreases draw range)
+            constexpr F32 MAX_INCREMENT = 0.05f;
+            F32 increment = MAX_INCREMENT * llmax(-(F32)sys_budget_debt.value() / (F32)budget_target.value(), 0.f);
+            sSysMemoryFactor += increment * LLFrameTimer::getFrameDeltaTimeF32();
+        }
+        sSysMemoryFactor = llclamp(sSysMemoryFactor, 1.f, 2.f);
+    }
+    else
+    {
+        // Only start ramping down when we have breathing room.
+        // This should be under the value of isSystemMemoryLow to not throw texture
+        // bias into 1.5+ territory each time we fluctuate around isSystemMemoryLow's
+        // threshold.
+        const S32Megabytes MEM_THRESHOLD = MEM_LOW_THRESHOLD + S32Megabytes(150);
+        if (free_sys_mem > MEM_THRESHOLD && sSysMemoryFactor > 1.f)
+        {
+            // Ramp down factor over time.
+            constexpr F32 DECREMENT = 0.02f;
+            sSysMemoryFactor -= DECREMENT * LLFrameTimer::getFrameDeltaTimeF32();
+            sSysMemoryFactor = llclamp(sSysMemoryFactor, 1.f, 2.f);
+        }
+    }
+    was_low = is_sys_low;
+
+    return sSysMemoryFactor;
+}
+
 #if LL_WINDOWS
 //static
 U32Megabytes LLMemory::getAvailableCommitMemMB()
diff --git a/indra/llcommon/llmemory.h b/indra/llcommon/llmemory.h
index 290f6e03d1..efcd7aadc4 100644
--- a/indra/llcommon/llmemory.h
+++ b/indra/llcommon/llmemory.h
@@ -4,7 +4,7 @@
  *
  * $LicenseInfo:firstyear=2002&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2010, Linden Research, Inc.
+ * Copyright (C) 2026, 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
@@ -27,6 +27,7 @@
 #define LLMEMORY_H
 
 #include "linden_common.h"
+#include "llframetimer.h"
 #include "llunits.h"
 #include "stdtypes.h"
 #if !LL_WINDOWS
@@ -428,6 +429,7 @@ public:
     static void initMaxHeapSizeGB(F32Gigabytes max_heap_size);
     static void updateMemoryInfo() ;
     static void logMemoryInfo(bool update = false);
+    static F32 getSystemMemoryBudgetFactor();
 
 #if LL_WINDOWS
     // Commit charge is a Windows-only concept, combines page file and ram
@@ -437,6 +439,7 @@ public:
     static U32Kilobytes getMaxMemKB() ;
     static U32Kilobytes getAllocatedMemKB() ;
 private:
+    static void updateFreeSystemMemory();
     // LLMemoryInfo directly updates memory stats
     friend class LLMemoryInfo;
 
@@ -447,6 +450,10 @@ private:
     static U32Kilobytes sAllocatedPageSizeInKB ;
 
     static U32Kilobytes sMaxHeapSizeInKB;
+
+    static LLFrameTimer sMemoryCheckTimer;
+    static F32 sSysMemoryFactor;
+    static U32 sFactorLastFrameCount;
 };
 
 // LLRefCount moved to llrefcount.h
diff --git a/indra/llcommon/llsys.cpp b/indra/llcommon/llsys.cpp
index 568a6b36dc..bc48fc0fd2 100644
--- a/indra/llcommon/llsys.cpp
+++ b/indra/llcommon/llsys.cpp
@@ -4,7 +4,7 @@
  *
  * $LicenseInfo:firstyear=2002&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2010, Linden Research, Inc.
+ * Copyright (C) 2026, 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
diff --git a/indra/llcommon/llsys.h b/indra/llcommon/llsys.h
index 709fb29a82..0abbe047ad 100644
--- a/indra/llcommon/llsys.h
+++ b/indra/llcommon/llsys.h
@@ -4,7 +4,7 @@
  *
  * $LicenseInfo:firstyear=2001&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2010, Linden Research, Inc.
+ * Copyright (C) 2026, 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
@@ -134,12 +134,12 @@ public:
     static U32Kilobytes getHardwareMemSize(); // Because some Mac linkers won't let us reference extern gSysMemory from a different lib.
 #endif
 
-    // Updates LLMemory's values (which ones is OS specific).
+    // Updates LLMemory's values.
     static void updateAvailableMemory();
 
     // Retrieve a map of memory statistics. The keys of the map are platform-
-    // dependent. The values are in kilobytes to try to avoid integer overflow.
-    // On windows updates LLMemory values.
+    // dependent.
+    // On Windows updates LLMemory values.
     LLSD getStatsMap() const;
 
     // Re-fetch memory data (as reported by stream() and getStatsMap()) from the
diff --git a/indra/newview/llappviewerwin32.cpp b/indra/newview/llappviewerwin32.cpp
index 5c2594e85c..8a9ddbcde6 100644
--- a/indra/newview/llappviewerwin32.cpp
+++ b/indra/newview/llappviewerwin32.cpp
@@ -82,6 +82,7 @@
 #include "BugSplat.h"
 #include "boost/json.hpp"                 // Boost.Json
 #include "llagent.h"                // for agent location
+#include "llmemory.h"
 #include "llstartup.h"
 #include "llviewerregion.h"
 #include "llvoavatarself.h"         // for agent name
@@ -181,11 +182,15 @@ namespace
             sBugSplatSender->setAttribute(WCSTR(L"VRAM"), WCSTR(STRINGIZE(gGLManager.mVRAM)));
             sBugSplatSender->setAttribute(WCSTR(L"RAM"), WCSTR(STRINGIZE(gSysMemory.getPhysicalMemoryKB().value())));
 
-            // Memory usage at crash time (can be 1s obsolete)
-            sBugSplatSender->setAttribute(WCSTR(L"MemAllocatedKB"), WCSTR(std::to_string(LLMemory::getAllocatedMemKB().value())));
-            sBugSplatSender->setAttribute(WCSTR(L"MemAvailableKB"), WCSTR(std::to_string(LLMemory::getAvailableMemKB().value())));
-            sBugSplatSender->setAttribute(WCSTR(L"MemMaxPhysicalKB"), WCSTR(std::to_string(LLMemory::getMaxMemKB().value())));
-            sBugSplatSender->setAttribute(WCSTR(L"MemAvailCommitMB"), WCSTR(std::to_string(LLMemory::getAvailableCommitMemMB().value())));
+            const U32 avail_kb = LLMemory::getAvailableMemKB().value();
+            if (avail_kb != U32_MAX) // filter out initial values, if one is not set, all are not set
+            {
+                // Memory usage at crash time (can be 1s obsolete)
+                sBugSplatSender->setAttribute(WCSTR(L"MemAllocatedKB"), WCSTR(std::to_string(LLMemory::getAllocatedMemKB().value())));
+                sBugSplatSender->setAttribute(WCSTR(L"MemAvailableKB"), WCSTR(std::to_string(LLMemory::getAvailableMemKB().value())));
+                sBugSplatSender->setAttribute(WCSTR(L"MemMaxPhysicalKB"), WCSTR(std::to_string(LLMemory::getMaxMemKB().value())));
+                sBugSplatSender->setAttribute(WCSTR(L"MemAvailCommitMB"), WCSTR(std::to_string(LLMemory::getAvailableCommitMemMB().value())));
+            }
 
             if (gAgent.getRegion())
             {
diff --git a/indra/newview/llviewerdisplay.cpp b/indra/newview/llviewerdisplay.cpp
index 9f1b0d75f3..0d50ba6fe2 100644
--- a/indra/newview/llviewerdisplay.cpp
+++ b/indra/newview/llviewerdisplay.cpp
@@ -217,6 +217,11 @@ void display_update_camera()
     {
         final_far *= 0.5f;
     }
+    // When system memory is critically low or recovering, shrink draw distance.
+    else if (const F32 mem_factor = LLMemory::getSystemMemoryBudgetFactor(); mem_factor > 1.f)
+    {
+        final_far = llmax(32.f, final_far / mem_factor);
+    }
     LLViewerCamera::getInstance()->setFar(final_far);
     LLVOAvatar::sRenderDistance = llclamp(final_far, 16.f, 256.f);
     gViewerWindow->setup3DRender();
diff --git a/indra/newview/llviewermessage.cpp b/indra/newview/llviewermessage.cpp
index 09f17fec40..8863dfb501 100644
--- a/indra/newview/llviewermessage.cpp
+++ b/indra/newview/llviewermessage.cpp
@@ -40,6 +40,7 @@
 #include "llinventorydefines.h"
 #include "lllslconstants.h"
 #include "llmaterialtable.h"
+#include "llmemory.h"
 #include "llregionhandle.h"
 #include "llsd.h"
 #include "llsdserialize.h"
@@ -3371,6 +3372,13 @@ void send_agent_update(bool force_send, bool send_reliable)
 
     static F32 last_draw_disatance_step = 1024;
     F32 memory_limited_draw_distance = gAgentCamera.mDrawDistance;
+    const F32 mem_factor = LLMemory::getSystemMemoryBudgetFactor();
+    if (mem_factor > 1.f)
+    {
+        // We are critically low on memory or recovering,
+        // limit requested draw distance
+        memory_limited_draw_distance = llmax(gAgentCamera.mDrawDistance / mem_factor, gAgentCamera.mDrawDistance / 2.f);
+    }
 
     if (tp_state == LLAgent::TELEPORT_ARRIVING || LLStartUp::getStartupState() < STATE_MISC)
     {
diff --git a/indra/newview/llvocache.cpp b/indra/newview/llvocache.cpp
index f3efe3f3bb..e513a3813f 100644
--- a/indra/newview/llvocache.cpp
+++ b/indra/newview/llvocache.cpp
@@ -32,6 +32,7 @@
 #include "lldrawable.h"
 #include "llviewerregion.h"
 #include "llagentcamera.h"
+#include "llmemory.h"
 #include "llsdserialize.h"
 #include "llworld.h" // For LLWorld::getInstance()
 //static variables
@@ -488,6 +489,13 @@ void LLVOCacheEntry::updateDebugSettings()
     static const F32 MIN_RADIUS = 1.0f;
 
     F32 draw_radius = gAgentCamera.mDrawDistance;
+    const F32 mem_factor = LLMemory::getSystemMemoryBudgetFactor();
+    if (mem_factor > 1.f)
+    {
+        // Factor is intended to go from 1.0 to 2.0
+        // For safety cap reduction at 50%, we don't want to go below half of draw distance
+        draw_radius = llmax(draw_radius / mem_factor, draw_radius / 2.f);
+    }
     const F32 clamped_min_radius = llclamp((F32) min_radius, MIN_RADIUS, draw_radius); // [1, mDrawDistance]
     sNearRadius = MIN_RADIUS + ((clamped_min_radius - MIN_RADIUS) * adjust_factor);