1 files changed, 28 insertions, 20 deletions

diff --git a/indra/newview/llviewertexture.cpp b/indra/newview/llviewertexture.cpp
index bb16fec32a..d16656abfc 100644
--- a/indra/newview/llviewertexture.cpp
+++ b/indra/newview/llviewertexture.cpp
@@ -511,12 +511,33 @@ void LLViewerTexture::updateClass()
 
     F32 over_pct = (used - target) / target;
 
-    bool is_low = over_pct > 0.f;
+    bool is_sys_low = isSystemMemoryLow();
+    bool is_low = is_sys_low || over_pct > 0.f;
 
-    if (isSystemMemoryLow())
+    static bool was_low = false;
+    static bool was_sys_low = false;
+
+    if (is_low && !was_low)
+    {
+        // slam to 1.5 bias the moment we hit low memory (discards off screen textures immediately)
+        sDesiredDiscardBias = llmax(sDesiredDiscardBias, 1.5f);
+
+        if (is_sys_low)
+        { // if we're low on system memory, emergency purge off screen textures to avoid a death spiral
+            LL_WARNS() << "Low system memory detected, emergency downrezzing off screen textures" << LL_ENDL;
+            for (auto& image : gTextureList)
+            {
+                gTextureList.updateImageDecodePriority(image, false /*will modify gTextureList otherwise!*/);
+            }
+        }
+    }
+
+    was_low = is_low;
+    was_sys_low = is_sys_low;
+
+    if (is_low)
     {
-        is_low = true;
-        // System RAM is low -> ramp up discard bias over time to free memory
+        // ramp up discard bias over time to free memory
         if (sEvaluationTimer.getElapsedTimeF32() > MEMORY_CHECK_WAIT_TIME)
         {
             static LLCachedControl<F32> low_mem_min_discard_increment(gSavedSettings, "RenderLowMemMinDiscardIncrement", .1f);
@@ -526,29 +547,16 @@ void LLViewerTexture::updateClass()
     }
     else
     {
-        sDesiredDiscardBias = llmax(sDesiredDiscardBias, 1.f + over_pct);
+        // don't execute above until the slam to 1.5 has a chance to take effect
+        sEvaluationTimer.reset();
 
+        // lower discard bias over time when free memory is available
         if (sDesiredDiscardBias > 1.f && over_pct < 0.f)
         {
             sDesiredDiscardBias -= gFrameIntervalSeconds * 0.01f;
         }
     }
 
-    static bool was_low = false;
-    if (is_low && !was_low)
-    {
-        LL_WARNS() << "Low system memory detected, emergency downrezzing off screen textures" << LL_ENDL;
-        sDesiredDiscardBias = llmax(sDesiredDiscardBias, 1.5f);
-
-        for (auto& image : gTextureList)
-        {
-            gTextureList.updateImageDecodePriority(image, false /*will modify gTextureList otherwise!*/);
-        }
-    }
-
-    was_low = is_low;
-
-
     // set to max discard bias if the window has been backgrounded for a while
     static bool was_backgrounded = false;
     static LLFrameTimer backgrounded_timer;