bg fixes - without approx free

Author: byrnedj

cachelib/allocator/CacheAllocator-inl.h

@@ -385,7 +385,7 @@ template <typename CacheTrait>
 bool CacheAllocator<CacheTrait>::shouldWakeupBgEvictor(TierId tid, PoolId pid, ClassId cid) {
   // TODO: should we also work on lower tiers? should we have separate set of params?
   if (tid == 1) return false;
-  return getACStats(tid, pid, cid).approxFreePercent <= config_.lowEvictionAcWatermark;
+  return getACStats(tid, pid, cid).usageFraction()*100 <= config_.lowEvictionAcWatermark;
 }
 
 template <typename CacheTrait>

cachelib/allocator/CacheAllocator.h

@@ -1980,9 +1980,9 @@ auto& mmContainer = getMMContainer(tid, pid, cid);
         if (candidate->markMoving(true)) {
           mmContainer.remove(itr);
           candidates.push_back(candidate);
+        } else {
+            ++itr;
         }
-
-        ++itr;
       }
     });
 

cachelib/allocator/FreeThresholdStrategy.cpp

@@ -36,12 +36,12 @@ std::vector<size_t> FreeThresholdStrategy::calculateBatchSizes(
   std::vector<size_t> batches{};
   for (auto [tid, pid, cid] : acVec) {
     auto stats = cache.getACStats(tid, pid, cid);
-    if (stats.approxFreePercent >= highEvictionAcWatermark) {
+    if (stats.usageFraction()*100 >= highEvictionAcWatermark) {
       batches.push_back(0);
     } else {
-      auto toFreeMemPercent = highEvictionAcWatermark - stats.approxFreePercent;
+      auto toFreeMemPercent = highEvictionAcWatermark - stats.usageFraction()*100;
       auto toFreeItems = static_cast<size_t>(
-          toFreeMemPercent * stats.memorySize / stats.allocSize);
+          toFreeMemPercent * (stats.totalSlabs() * Slab::kSize) / stats.allocSize);
       batches.push_back(toFreeItems);
     }
   }

cachelib/allocator/PromotionStrategy.h

@@ -40,12 +40,12 @@ class PromotionStrategy : public BackgroundMoverStrategy {
     for (auto [tid, pid, cid] : acVec) {
       XDCHECK(tid > 0);
       auto stats = cache.getACStats(tid - 1, pid, cid);
-      if (stats.approxFreePercent < promotionAcWatermark)
+      if (stats.usageFraction()*100 < promotionAcWatermark)
         batches.push_back(0);
       else {
         auto maxPossibleItemsToPromote = static_cast<size_t>(
-            (promotionAcWatermark - stats.approxFreePercent) *
-            stats.memorySize / stats.allocSize);
+            (promotionAcWatermark - stats.usageFraction()*100) *
+            (stats.totalSlabs() * Slab::kSize) / stats.allocSize);
         batches.push_back(maxPossibleItemsToPromote);
       }
     }

cachelib/allocator/tests/AllocatorMemoryTiersTest.h

@@ -124,12 +124,12 @@ class AllocatorMemoryTiersTest : public AllocatorTest<AllocatorT> {
     const auto& mpStats = allocator->getPoolByTid(poolId, 0).getStats(); 
     //cache is 10MB should move about 1MB to reach 10% free
     uint32_t approxEvict = (1024*1024)/mpStats.acStats.at(cid).allocSize;
-    while (stats.evictionStats.numMovedItems < approxEvict*0.95 && slabStats.approxFreePercent >= 9.5) {
+    while (stats.evictionStats.numMovedItems < approxEvict*0.95 && slabStats.usageFraction() >= 0.095) {
         std::this_thread::sleep_for(std::chrono::seconds(1));
         stats = allocator->getGlobalCacheStats();
         slabStats = allocator->getACStats(0,0,cid);
     }
-    ASSERT_GE(slabStats.approxFreePercent,9.5);
+    ASSERT_GE(slabStats.usageFraction(),0.095);
 
     auto perclassEstats = allocator->getBackgroundMoverClassStats(MoverDir::Evict);
     auto perclassPstats = allocator->getBackgroundMoverClassStats(MoverDir::Promote);