#3364 Fix update rate being stuck high due to bias

if bias stays unchanged at 4.f, there is no reason to keep refreshing
at high rate.

Author: akleshchev

indra/newview/llviewertexture.cpp

@@ -87,6 +87,7 @@ S32 LLViewerTexture::sRawCount = 0;
 S32 LLViewerTexture::sAuxCount = 0;
 LLFrameTimer LLViewerTexture::sEvaluationTimer;
 F32 LLViewerTexture::sDesiredDiscardBias = 0.f;
+U32 LLViewerTexture::sBiasTexturesUpdated = 0;
 
 S32 LLViewerTexture::sMaxSculptRez = 128; //max sculpt image size
 constexpr S32 MAX_CACHED_RAW_IMAGE_AREA = 64 * 64;
@@ -518,6 +519,7 @@ void LLViewerTexture::updateClass()
 
     bool is_sys_low = isSystemMemoryLow();
     bool is_low = is_sys_low || over_pct > 0.f;
+    F32 discard_bias = sDesiredDiscardBias;
 
     static bool was_low = false;
     static bool was_sys_low = false;
@@ -604,6 +606,12 @@ void LLViewerTexture::updateClass()
     }
 
     sDesiredDiscardBias = llclamp(sDesiredDiscardBias, 1.f, 4.f);
+    if (discard_bias != sDesiredDiscardBias)
+    {
+        // bias changed, reset texture update counter to
+        // let updates happen at an increased rate.
+        sBiasTexturesUpdated = 0;
+    }
 
     LLViewerTexture::sFreezeImageUpdates = false;
 }

indra/newview/llviewertexture.h

@@ -220,6 +220,7 @@ class LLViewerTexture : public LLGLTexture
     static S32 sAuxCount;
     static LLFrameTimer sEvaluationTimer;
     static F32 sDesiredDiscardBias;
+    static U32 sBiasTexturesUpdated;
     static S32 sMaxSculptRez ;
     static U32 sMinLargeImageSize ;
     static U32 sMaxSmallImageSize ;

indra/newview/llviewertexturelist.cpp

@@ -1198,10 +1198,17 @@ F32 LLViewerTextureList::updateImagesFetchTextures(F32 max_time)
 
     //update MIN_UPDATE_COUNT or 5% of other textures, whichever is greater
     update_count = llmax((U32) MIN_UPDATE_COUNT, (U32) mUUIDMap.size()/20);
-    if (LLViewerTexture::sDesiredDiscardBias > 1.f)
+    if (LLViewerTexture::sDesiredDiscardBias > 1.f
+        && LLViewerTexture::sBiasTexturesUpdated < (U32)mUUIDMap.size())
     {
-        // we are over memory target, update more agresively
+        // We are over memory target. Bias affects discard rates, so update
+        // existing textures agresively to free memory faster.
         update_count = (S32)(update_count * LLViewerTexture::sDesiredDiscardBias);
+
+        // This isn't particularly precise and can overshoot, but it doesn't need
+        // to be, just making sure it did a full circle and doesn't get stuck updating
+        // at bias = 4 with 4 times the rate permanently.
+        LLViewerTexture::sBiasTexturesUpdated += update_count;
     }
     update_count = llmin(update_count, (U32) mUUIDMap.size());