Preload l0 index partitions

Summary:
This fixes the existing logic for pinning l0 index partitions. The patch preloads the partitions into block cache and pin them if they belong to level 0 and pin_l0 is set.

The drawback is that it does many small IOs when preloading all the partitions into the cache is direct io is enabled. Working for a solution for that.
Closes https://github.com/facebook/rocksdb/pull/2661

Differential Revision: D5554010

Pulled By: maysamyabandeh

fbshipit-source-id: 1e6f32a3524d71355c77d4138516dcfb601ca7b2

HISTORY.md

@@ -1,5 +1,7 @@
 # Rocksdb Change Log
 ## Unreleased
+
+## 5.7.8 (08/14/2017)
 ### New Features
 * Add Iterator::Refresh(), which allows users to update the iterator state so that they can avoid some initialization costs of recreating iterators.
 * Replace dynamic_cast<> (except unit test) so people can choose to build with RTTI off. With make, release mode is by default built with -fno-rtti and debug mode is built without it. Users can override it by setting USE_RTTI=0 or 1.

include/rocksdb/version.h

@@ -5,7 +5,7 @@
 #pragma once
 
 #define ROCKSDB_MAJOR 5
-#define ROCKSDB_MINOR 7
+#define ROCKSDB_MINOR 8
 #define ROCKSDB_PATCH 0
 
 // Do not use these. We made the mistake of declaring macros starting with

table/block_based_table_reader.cc

@@ -186,23 +186,87 @@ class PartitionIndexReader : public IndexReader, public Cleanable {
     // Filters are already checked before seeking the index
     const bool skip_filters = true;
     const bool is_index = true;
-    Cleanable* block_cache_cleaner = nullptr;
-    const bool pin_cached_indexes =
-        level_ == 0 &&
-        table_->rep_->table_options.pin_l0_filter_and_index_blocks_in_cache;
-    if (pin_cached_indexes) {
-      // Keep partition indexes into the cache as long as the partition index
-      // reader object is alive
-      block_cache_cleaner = this;
-    }
     return NewTwoLevelIterator(
         new BlockBasedTable::BlockEntryIteratorState(
             table_, ReadOptions(), icomparator_, skip_filters, is_index,
-            block_cache_cleaner),
+            partition_map_.size() ? &partition_map_ : nullptr),
         index_block_->NewIterator(icomparator_, nullptr, true));
     // TODO(myabandeh): Update TwoLevelIterator to be able to make use of
-    // on-stack
-    // BlockIter while the state is on heap
+    // on-stack BlockIter while the state is on heap. Currentlly it assumes
+    // the first level iter is always on heap and will attempt to delete it
+    // in its destructor.
+  }
+
+  virtual void CacheDependencies(bool pin) override {
+    // Before read partitions, prefetch them to avoid lots of IOs
+    auto rep = table_->rep_;
+    BlockIter biter;
+    BlockHandle handle;
+    index_block_->NewIterator(icomparator_, &biter, true);
+    // Index partitions are assumed to be consecuitive. Prefetch them all.
+    // Read the first block offset
+    biter.SeekToFirst();
+    Slice input = biter.value();
+    Status s = handle.DecodeFrom(&input);
+    assert(s.ok());
+    if (!s.ok()) {
+      ROCKS_LOG_WARN(rep->ioptions.info_log,
+                     "Could not read first index partition");
+      return;
+    }
+    uint64_t prefetch_off = handle.offset();
+
+    // Read the last block's offset
+    biter.SeekToLast();
+    input = biter.value();
+    s = handle.DecodeFrom(&input);
+    assert(s.ok());
+    if (!s.ok()) {
+      ROCKS_LOG_WARN(rep->ioptions.info_log,
+                     "Could not read last index partition");
+      return;
+    }
+    uint64_t last_off = handle.offset() + handle.size() + kBlockTrailerSize;
+    uint64_t prefetch_len = last_off - prefetch_off;
+    std::unique_ptr<FilePrefetchBuffer> prefetch_buffer;
+    auto& file = table_->rep_->file;
+    prefetch_buffer.reset(new FilePrefetchBuffer());
+    s = prefetch_buffer->Prefetch(file.get(), prefetch_off, prefetch_len);
+
+    // After prefetch, read the partitions one by one
+    biter.SeekToFirst();
+    auto ro = ReadOptions();
+    Cache* block_cache = rep->table_options.block_cache.get();
+    for (; biter.Valid(); biter.Next()) {
+      input = biter.value();
+      s = handle.DecodeFrom(&input);
+      assert(s.ok());
+      if (!s.ok()) {
+        ROCKS_LOG_WARN(rep->ioptions.info_log,
+                       "Could not read index partition");
+        continue;
+      }
+
+      BlockBasedTable::CachableEntry<Block> block;
+      Slice compression_dict;
+      if (rep->compression_dict_block) {
+        compression_dict = rep->compression_dict_block->data;
+      }
+      const bool is_index = true;
+      s = table_->MaybeLoadDataBlockToCache(prefetch_buffer.get(), rep, ro,
+                                            handle, compression_dict, &block,
+                                            is_index);
+
+      if (s.ok() && block.value != nullptr) {
+        assert(block.cache_handle != nullptr);
+        if (pin) {
+          partition_map_[handle.offset()] = block;
+          RegisterCleanup(&ReleaseCachedEntry, block_cache, block.cache_handle);
+        } else {
+          block_cache->Release(block.cache_handle);
+        }
+      }
+    }
   }
 
   virtual size_t size() const override { return index_block_->size(); }
@@ -222,13 +286,12 @@ class PartitionIndexReader : public IndexReader, public Cleanable {
                        const int level)
       : IndexReader(icomparator, stats),
         table_(table),
-        index_block_(std::move(index_block)),
-        level_(level) {
+        index_block_(std::move(index_block)) {
     assert(index_block_ != nullptr);
   }
   BlockBasedTable* table_;
   std::unique_ptr<Block> index_block_;
-  int level_;
+  std::map<uint64_t, BlockBasedTable::CachableEntry<Block>> partition_map_;
 };
 
 // Index that allows binary search lookup for the first key of each block.
@@ -708,10 +771,9 @@ Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions,
   } else {
     if (found_range_del_block && !rep->range_del_handle.IsNull()) {
       ReadOptions read_options;
-      // TODO: try to use prefetched buffer too.
-      s = MaybeLoadDataBlockToCache(rep, read_options, rep->range_del_handle,
-                                    Slice() /* compression_dict */,
-                                    &rep->range_del_entry);
+      s = MaybeLoadDataBlockToCache(
+          prefetch_buffer.get(), rep, read_options, rep->range_del_handle,
+          Slice() /* compression_dict */, &rep->range_del_entry);
       if (!s.ok()) {
         ROCKS_LOG_WARN(
             rep->ioptions.info_log,
@@ -740,21 +802,22 @@ Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions,
   // Always prefetch index and filter for level 0
   if (table_options.cache_index_and_filter_blocks) {
     if (prefetch_index_and_filter_in_cache || level == 0) {
+      const bool pin =
+          rep->table_options.pin_l0_filter_and_index_blocks_in_cache &&
+          level == 0;
       assert(table_options.block_cache != nullptr);
       // Hack: Call NewIndexIterator() to implicitly add index to the
       // block_cache
 
-      // if pin_l0_filter_and_index_blocks_in_cache is true and this is
-      // a level0 file, then we will pass in this pointer to rep->index
-      // to NewIndexIterator(), which will save the index block in there
-      // else it's a nullptr and nothing special happens
-      CachableEntry<IndexReader>* index_entry = nullptr;
-      if (rep->table_options.pin_l0_filter_and_index_blocks_in_cache &&
-          level == 0) {
-        index_entry = &rep->index_entry;
-      }
+      CachableEntry<IndexReader> index_entry;
       unique_ptr<InternalIterator> iter(
-          new_table->NewIndexIterator(ReadOptions(), nullptr, index_entry));
+          new_table->NewIndexIterator(ReadOptions(), nullptr, &index_entry));
+      index_entry.value->CacheDependencies(pin);
+      if (pin) {
+        rep->index_entry = std::move(index_entry);
+      } else {
+        index_entry.Release(table_options.block_cache.get());
+      }
       s = iter->status();
 
       if (s.ok()) {
@@ -764,8 +827,7 @@ Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions,
         // a level0 file, then save it in rep_->filter_entry; it will be
         // released in the destructor only, hence it will be pinned in the
         // cache while this reader is alive
-        if (rep->table_options.pin_l0_filter_and_index_blocks_in_cache &&
-            level == 0) {
+        if (pin) {
           rep->filter_entry = filter_entry;
           if (rep->filter_entry.value != nullptr) {
             rep->filter_entry.value->SetLevel(level);
@@ -1305,8 +1367,8 @@ InternalIterator* BlockBasedTable::NewDataBlockIterator(
     if (rep->compression_dict_block) {
       compression_dict = rep->compression_dict_block->data;
     }
-    s = MaybeLoadDataBlockToCache(rep, ro, handle, compression_dict, &block,
-                                  is_index);
+    s = MaybeLoadDataBlockToCache(nullptr /*prefetch_buffer*/, rep, ro, handle,
+                                  compression_dict, &block, is_index);
   }
 
   // Didn't get any data from block caches.
@@ -1355,8 +1417,9 @@ InternalIterator* BlockBasedTable::NewDataBlockIterator(
 }
 
 Status BlockBasedTable::MaybeLoadDataBlockToCache(
-    Rep* rep, const ReadOptions& ro, const BlockHandle& handle,
-    Slice compression_dict, CachableEntry<Block>* block_entry, bool is_index) {
+    FilePrefetchBuffer* prefetch_buffer, Rep* rep, const ReadOptions& ro,
+    const BlockHandle& handle, Slice compression_dict,
+    CachableEntry<Block>* block_entry, bool is_index) {
   const bool no_io = (ro.read_tier == kBlockCacheTier);
   Cache* block_cache = rep->table_options.block_cache.get();
   Cache* block_cache_compressed =
@@ -1392,12 +1455,11 @@ Status BlockBasedTable::MaybeLoadDataBlockToCache(
       std::unique_ptr<Block> raw_block;
       {
         StopWatch sw(rep->ioptions.env, statistics, READ_BLOCK_GET_MICROS);
-        s = ReadBlockFromFile(rep->file.get(), nullptr /* prefetch_buffer*/,
-                              rep->footer, ro, handle, &raw_block,
-                              rep->ioptions, block_cache_compressed == nullptr,
-                              compression_dict, rep->persistent_cache_options,
-                              rep->global_seqno,
-                              rep->table_options.read_amp_bytes_per_bit);
+        s = ReadBlockFromFile(
+            rep->file.get(), prefetch_buffer, rep->footer, ro, handle,
+            &raw_block, rep->ioptions, block_cache_compressed == nullptr,
+            compression_dict, rep->persistent_cache_options, rep->global_seqno,
+            rep->table_options.read_amp_bytes_per_bit);
       }
 
       if (s.ok()) {
@@ -1420,14 +1482,14 @@ Status BlockBasedTable::MaybeLoadDataBlockToCache(
 BlockBasedTable::BlockEntryIteratorState::BlockEntryIteratorState(
     BlockBasedTable* table, const ReadOptions& read_options,
     const InternalKeyComparator* icomparator, bool skip_filters, bool is_index,
-    Cleanable* block_cache_cleaner)
+    std::map<uint64_t, CachableEntry<Block>>* block_map)
     : TwoLevelIteratorState(table->rep_->ioptions.prefix_extractor != nullptr),
       table_(table),
       read_options_(read_options),
       icomparator_(icomparator),
       skip_filters_(skip_filters),
       is_index_(is_index),
-      block_cache_cleaner_(block_cache_cleaner) {}
+      block_map_(block_map) {}
 
 InternalIterator*
 BlockBasedTable::BlockEntryIteratorState::NewSecondaryIterator(
@@ -1436,23 +1498,15 @@ BlockBasedTable::BlockEntryIteratorState::NewSecondaryIterator(
   BlockHandle handle;
   Slice input = index_value;
   Status s = handle.DecodeFrom(&input);
-  auto iter = NewDataBlockIterator(table_->rep_, read_options_, handle, nullptr,
-                                   is_index_, s);
-  if (block_cache_cleaner_) {
-    uint64_t offset = handle.offset();
-    {
-      ReadLock rl(&cleaner_mu);
-      if (cleaner_set.find(offset) != cleaner_set.end()) {
-        // already have a reference to the block cache objects
-        return iter;
-      }
-    }
-    WriteLock wl(&cleaner_mu);
-    cleaner_set.insert(offset);
-    // Keep the data into cache until the cleaner cleansup
-    iter->DelegateCleanupsTo(block_cache_cleaner_);
-  }
-  return iter;
+  auto rep = table_->rep_;
+  if (block_map_) {
+    auto block = block_map_->find(handle.offset());
+    assert(block != block_map_->end());
+    return block->second.value->NewIterator(&rep->internal_comparator, nullptr,
+                                            true, rep->ioptions.statistics);
+  }
+  return NewDataBlockIterator(rep, read_options_, handle, nullptr, is_index_,
+                              s);
 }
 
 bool BlockBasedTable::BlockEntryIteratorState::PrefixMayMatch(

table/block_based_table_reader.h

@@ -181,6 +181,8 @@ class BlockBasedTable : public TableReader {
     // that was allocated in block cache.
     virtual size_t ApproximateMemoryUsage() const = 0;
 
+    virtual void CacheDependencies(bool /* unused */) {}
+
    protected:
     const InternalKeyComparator* icomparator_;
 
@@ -227,7 +229,8 @@ class BlockBasedTable : public TableReader {
   // @param block_entry value is set to the uncompressed block if found. If
   //    in uncompressed block cache, also sets cache_handle to reference that
   //    block.
-  static Status MaybeLoadDataBlockToCache(Rep* rep, const ReadOptions& ro,
+  static Status MaybeLoadDataBlockToCache(FilePrefetchBuffer* prefetch_buffer,
+                                          Rep* rep, const ReadOptions& ro,
                                           const BlockHandle& handle,
                                           Slice compression_dict,
                                           CachableEntry<Block>* block_entry,
@@ -345,11 +348,11 @@ class BlockBasedTable : public TableReader {
 // Maitaning state of a two-level iteration on a partitioned index structure
 class BlockBasedTable::BlockEntryIteratorState : public TwoLevelIteratorState {
  public:
-  BlockEntryIteratorState(BlockBasedTable* table,
-                          const ReadOptions& read_options,
-                          const InternalKeyComparator* icomparator,
-                          bool skip_filters, bool is_index = false,
-                          Cleanable* block_cache_cleaner = nullptr);
+  BlockEntryIteratorState(
+      BlockBasedTable* table, const ReadOptions& read_options,
+      const InternalKeyComparator* icomparator, bool skip_filters,
+      bool is_index = false,
+      std::map<uint64_t, CachableEntry<Block>>* block_map = nullptr);
   InternalIterator* NewSecondaryIterator(const Slice& index_value) override;
   bool PrefixMayMatch(const Slice& internal_key) override;
   bool KeyReachedUpperBound(const Slice& internal_key) override;
@@ -362,8 +365,7 @@ class BlockBasedTable::BlockEntryIteratorState : public TwoLevelIteratorState {
   bool skip_filters_;
   // true if the 2nd level iterator is on indexes instead of on user data.
   bool is_index_;
-  Cleanable* block_cache_cleaner_;
-  std::set<uint64_t> cleaner_set;
+  std::map<uint64_t, CachableEntry<Block>>* block_map_;
   port::RWMutex cleaner_mu;
 };
 

table/table_test.cc

@@ -2174,7 +2174,7 @@ std::map<std::string, size_t> MockCache::marked_data_in_cache_;
 
 // Block cache can contain raw data blocks as well as general objects. If an
 // object depends on the table to be live, it then must be destructed before the
-// table is closed. This test makese sure that the only items remains in the
+// table is closed. This test makes sure that the only items remains in the
 // cache after the table is closed are raw data blocks.
 TEST_F(BlockBasedTableTest, NoObjectInCacheAfterTableClose) {
   for (auto index_type :