Adds createPutToken and switches findEviction

to utilize combined locking.

Author: byrnedj

cachelib/allocator/CacheAllocator.h

@@ -1481,11 +1481,11 @@ class CacheAllocator : public CacheBase {
   // Given an existing item, allocate a new one for the
   // existing one to later be moved into.
   //
-  // @param oldItem    the item we want to allocate a new item for
+  // @param item   reference to the item we want to allocate a new item for
   //
   // @return  handle to the newly allocated item
   //
-  WriteHandle allocateNewItemForOldItem(const Item& oldItem);
+  WriteHandle allocateNewItemForOldItem(const Item& item);
 
   // internal helper that grabs a refcounted handle to the item. This does
   // not record the access to reflect in the mmContainer.
@@ -1544,7 +1544,7 @@ class CacheAllocator : public CacheBase {
   // callback is responsible for copying the contents and fixing the semantics
   // of chained item.
   //
-  // @param oldItem     Reference to the item being moved
+  // @param oldItem     item being moved
   // @param newItemHdl  Reference to the handle of the new item being moved into
   //
   // @return true  If the move was completed, and the containers were updated
@@ -1980,18 +1980,14 @@ class CacheAllocator : public CacheBase {
   std::optional<bool> saveNvmCache();
   void saveRamCache();
 
-  static bool itemExclusivePredicate(const Item& item) {
-    return item.getRefCount() == 0;
+  static bool itemSlabMovePredicate(const Item& item) {
+    return item.isMoving() && item.getRefCount() == 0;
   }
 
   static bool itemExpiryPredicate(const Item& item) {
     return item.getRefCount() == 1 && item.isExpired();
   }
 
-  static bool parentEvictForSlabReleasePredicate(const Item& item) {
-    return item.getRefCount() == 1 && !item.isMoving();
-  }
-
   std::unique_ptr<Deserializer> createDeserializer();
 
   // Execute func on each item. `func` can throw exception but must ensure
@@ -3663,12 +3659,9 @@ CacheAllocator<CacheTrait>::getNextCandidate(PoolId pid,
               ? &toRecycle_->asChainedItem().getParentItem(compressor_)
               : toRecycle_;
 
-      const bool evictToNvmCache = shouldWriteToNvmCache(*candidate_);
-      auto putToken = evictToNvmCache
-                          ? nvmCache_->createPutToken(candidate_->getKey())
-                          : typename NvmCacheT::PutToken{};
+      auto putToken = createPutToken(*candidate_);
 
-      if (evictToNvmCache && !putToken.isValid()) {
+      if (shouldWriteToNvmCache(*candidate_) && !putToken.isValid()) {
         stats_.evictFailConcurrentFill.inc();
         ++itr;
         continue;
@@ -4291,13 +4284,13 @@ std::vector<std::string> CacheAllocator<CacheTrait>::dumpEvictionIterator(
   std::vector<std::string> content;
 
   auto& mm = *mmContainers_[pid][cid];
-  auto evictItr = mm.getEvictionIterator();
-  size_t i = 0;
-  while (evictItr && i < numItems) {
-    content.push_back(evictItr->toString());
-    ++evictItr;
-    ++i;
-  }
+
+  mm.withEvictionIterator([&content, numItems](auto&& itr) {
+    while (itr && content.size() < numItems) {
+      content.push_back(itr->toString());
+      ++itr;
+    }
+  });
 
   return content;
 }
@@ -4942,6 +4935,7 @@ bool CacheAllocator<CacheTrait>::moveForSlabRelease(Item& oldItem) {
 template <typename CacheTrait>
 typename CacheAllocator<CacheTrait>::WriteHandle
 CacheAllocator<CacheTrait>::allocateNewItemForOldItem(const Item& oldItem) {
+  XDCHECK(oldItem.isMoving());
   if (oldItem.isChainedItem()) {
     const Item& parentItem = oldItem.asChainedItem().getParentItem(compressor_);
 
@@ -4955,7 +4949,7 @@ CacheAllocator<CacheTrait>::allocateNewItemForOldItem(const Item& oldItem) {
     XDCHECK_EQ(newItemHdl->getSize(), oldChainedItem.getSize());
     XDCHECK_EQ(reinterpret_cast<uintptr_t>(&parentItem),
                reinterpret_cast<uintptr_t>(
-                   &oldChainedItem.getParentItem(compressor_)));
+                   &newItemHdl->asChainedItem().getParentItem(compressor_)));
 
     return newItemHdl;
   }

cachelib/allocator/MM2Q.h

@@ -66,6 +66,7 @@ class MM2Q {
   enum LruType { Warm, WarmTail, Hot, Cold, ColdTail, NumTypes };
 
   // Config class for MM2Q
+  // TODO: implement support for useCombinedLockForIterators
   struct Config {
     // Create from serialized config
     explicit Config(SerializationConfigType configState)

cachelib/allocator/tests/BaseAllocatorTest.h

@@ -4182,15 +4182,16 @@ class BaseAllocatorTest : public AllocatorTest<AllocatorT> {
   // Check that item is in the expected container.
   bool findItem(AllocatorT& allocator, typename AllocatorT::Item* item) {
     auto& container = allocator.getMMContainer(*item);
-    auto itr = container.getEvictionIterator();
     bool found = false;
-    while (itr) {
-      if (itr.get() == item) {
-        found = true;
-        break;
+    container.withEvictionIterator([&found, &item](auto&& itr) {
+      while (itr) {
+        if (itr.get() == item) {
+          found = true;
+          break;
+        }
+        ++itr;
       }
-      ++itr;
-    }
+    });
     return found;
   }
 
@@ -5482,8 +5483,12 @@ class BaseAllocatorTest : public AllocatorTest<AllocatorT> {
       ASSERT_TRUE(big->isInMMContainer());
 
       auto& mmContainer = alloc.getMMContainer(*big);
-      auto itr = mmContainer.getEvictionIterator();
-      ASSERT_EQ(big.get(), &(*itr));
+
+      typename AllocatorT::Item* evictionCandidate = nullptr;
+      mmContainer.withEvictionIterator(
+          [&evictionCandidate](auto&& itr) { evictionCandidate = itr.get(); });
+
+      ASSERT_EQ(big.get(), evictionCandidate);
 
       alloc.remove("hello");
     }
@@ -5497,8 +5502,11 @@ class BaseAllocatorTest : public AllocatorTest<AllocatorT> {
       ASSERT_TRUE(small2->isInMMContainer());
 
       auto& mmContainer = alloc.getMMContainer(*small2);
-      auto itr = mmContainer.getEvictionIterator();
-      ASSERT_EQ(small2.get(), &(*itr));
+
+      typename AllocatorT::Item* evictionCandidate = nullptr;
+      mmContainer.withEvictionIterator(
+          [&evictionCandidate](auto&& itr) { evictionCandidate = itr.get(); });
+      ASSERT_EQ(small2.get(), evictionCandidate);
 
       alloc.remove("hello");
     }