Add insert hints for each writebatch (facebook#5728)

Summary:
Add insert hints for each writebatch so that they can be used in concurrent write, and add write option to enable it.

Bench result (qps):

`./db_bench --benchmarks=fillseq -allow_concurrent_memtable_write=true -num=4000000 -batch-size=1 -threads=1 -db=/data3/ylj/tmp -write_buffer_size=536870912 -num_column_families=4`

master:

| batch size \ thread num | 1       | 2       | 4       | 8       |
| ----------------------- | ------- | ------- | ------- | ------- |
| 1                       | 387883  | 220790  | 308294  | 490998  |
| 10                      | 1397208 | 978911  | 1275684 | 1733395 |
| 100                     | 2045414 | 1589927 | 1798782 | 2681039 |
| 1000                    | 2228038 | 1698252 | 1839877 | 2863490 |

fillseq with writebatch hint:

| batch size \ thread num | 1       | 2       | 4       | 8       |
| ----------------------- | ------- | ------- | ------- | ------- |
| 1                       | 286005  | 223570  | 300024  | 466981  |
| 10                      | 970374  | 813308  | 1399299 | 1753588 |
| 100                     | 1962768 | 1983023 | 2676577 | 3086426 |
| 1000                    | 2195853 | 2676782 | 3231048 | 3638143 |
Pull Request resolved: facebook#5728

Differential Revision: D17297240

fbshipit-source-id: b053590a6d77871f1ef2f911a7bd013b3899b26c

Author: Jing118

db/c.cc

@@ -3224,6 +3224,11 @@ void rocksdb_writeoptions_set_low_pri(
   opt->rep.low_pri = v;
 }
 
+void rocksdb_writeoptions_set_memtable_insert_hint_per_batch(
+    rocksdb_writeoptions_t* opt, unsigned char v) {
+  opt->rep.memtable_insert_hint_per_batch = v;
+}
+
 rocksdb_compactoptions_t* rocksdb_compactoptions_create() {
   return new rocksdb_compactoptions_t;
 }

db/db_impl/db_impl_write.cc

@@ -174,7 +174,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
           &trim_history_scheduler_,
           write_options.ignore_missing_column_families, 0 /*log_number*/, this,
           true /*concurrent_memtable_writes*/, seq_per_batch_, w.batch_cnt,
-          batch_per_txn_);
+          batch_per_txn_, write_options.memtable_insert_hint_per_batch);
 
       PERF_TIMER_START(write_pre_and_post_process_time);
     }
@@ -397,7 +397,8 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
               &trim_history_scheduler_,
               write_options.ignore_missing_column_families, 0 /*log_number*/,
               this, true /*concurrent_memtable_writes*/, seq_per_batch_,
-              w.batch_cnt, batch_per_txn_);
+              w.batch_cnt, batch_per_txn_,
+              write_options.memtable_insert_hint_per_batch);
         }
       }
       if (seq_used != nullptr) {
@@ -564,7 +565,9 @@ Status DBImpl::PipelinedWriteImpl(const WriteOptions& write_options,
     w.status = WriteBatchInternal::InsertInto(
         &w, w.sequence, &column_family_memtables, &flush_scheduler_,
         &trim_history_scheduler_, write_options.ignore_missing_column_families,
-        0 /*log_number*/, this, true /*concurrent_memtable_writes*/);
+        0 /*log_number*/, this, true /*concurrent_memtable_writes*/,
+        false /*seq_per_batch*/, 0 /*batch_cnt*/, true /*batch_per_txn*/,
+        write_options.memtable_insert_hint_per_batch);
     if (write_thread_.CompleteParallelMemTableWriter(&w)) {
       MemTableInsertStatusCheck(w.status);
       versions_->SetLastSequence(w.write_group->last_sequence);
@@ -603,7 +606,8 @@ Status DBImpl::UnorderedWriteMemtable(const WriteOptions& write_options,
         &w, w.sequence, &column_family_memtables, &flush_scheduler_,
         &trim_history_scheduler_, write_options.ignore_missing_column_families,
         0 /*log_number*/, this, true /*concurrent_memtable_writes*/,
-        seq_per_batch_, sub_batch_cnt);
+        seq_per_batch_, sub_batch_cnt, true /*batch_per_txn*/,
+        write_options.memtable_insert_hint_per_batch);
 
     WriteStatusCheck(w.status);
     if (write_options.disableWAL) {

db/memtable.cc

@@ -469,7 +469,7 @@ MemTable::MemTableStats MemTable::ApproximateStats(const Slice& start_ikey,
 bool MemTable::Add(SequenceNumber s, ValueType type,
                    const Slice& key, /* user key */
                    const Slice& value, bool allow_concurrent,
-                   MemTablePostProcessInfo* post_process_info) {
+                   MemTablePostProcessInfo* post_process_info, void** hint) {
   // Format of an entry is concatenation of:
   //  key_size     : varint32 of internal_key.size()
   //  key bytes    : char[internal_key.size()]
@@ -547,7 +547,9 @@ bool MemTable::Add(SequenceNumber s, ValueType type,
     assert(post_process_info == nullptr);
     UpdateFlushState();
   } else {
-    bool res = table->InsertKeyConcurrently(handle);
+    bool res = (hint == nullptr)
+                   ? table->InsertKeyConcurrently(handle)
+                   : table->InsertKeyWithHintConcurrently(handle, hint);
     if (UNLIKELY(!res)) {
       return res;
     }

db/memtable.h

@@ -182,7 +182,8 @@ class MemTable {
   // the <key, seq> already exists.
   bool Add(SequenceNumber seq, ValueType type, const Slice& key,
            const Slice& value, bool allow_concurrent = false,
-           MemTablePostProcessInfo* post_process_info = nullptr);
+           MemTablePostProcessInfo* post_process_info = nullptr,
+           void** hint = nullptr);
 
   // Used to Get value associated with key or Get Merge Operands associated
   // with key.

db/write_batch.cc

@@ -39,6 +39,7 @@
 #include <stack>
 #include <stdexcept>
 #include <type_traits>
+#include <unordered_map>
 #include <vector>
 
 #include "db/column_family.h"
@@ -1225,6 +1226,22 @@ class MemTableInserter : public WriteBatch::Handler {
   DupDetector       duplicate_detector_;
   bool              dup_dectector_on_;
 
+  bool hint_per_batch_;
+  bool hint_created_;
+  // Hints for this batch
+  using HintMap = std::unordered_map<MemTable*, void*>;
+  using HintMapType = std::aligned_storage<sizeof(HintMap)>::type;
+  HintMapType hint_;
+
+  HintMap& GetHintMap() {
+    assert(hint_per_batch_);
+    if (!hint_created_) {
+      new (&hint_) HintMap();
+      hint_created_ = true;
+    }
+    return *reinterpret_cast<HintMap*>(&hint_);
+  }
+
   MemPostInfoMap& GetPostMap() {
     assert(concurrent_memtable_writes_);
     if(!post_info_created_) {
@@ -1258,7 +1275,7 @@ class MemTableInserter : public WriteBatch::Handler {
                    uint64_t recovering_log_number, DB* db,
                    bool concurrent_memtable_writes,
                    bool* has_valid_writes = nullptr, bool seq_per_batch = false,
-                   bool batch_per_txn = true)
+                   bool batch_per_txn = true, bool hint_per_batch = false)
       : sequence_(_sequence),
         cf_mems_(cf_mems),
         flush_scheduler_(flush_scheduler),
@@ -1282,7 +1299,9 @@ class MemTableInserter : public WriteBatch::Handler {
         write_before_prepare_(!batch_per_txn),
         unprepared_batch_(false),
         duplicate_detector_(),
-        dup_dectector_on_(false) {
+        dup_dectector_on_(false),
+        hint_per_batch_(hint_per_batch),
+        hint_created_(false) {
     assert(cf_mems_);
   }
 
@@ -1295,6 +1314,12 @@ class MemTableInserter : public WriteBatch::Handler {
       reinterpret_cast<MemPostInfoMap*>
         (&mem_post_info_map_)->~MemPostInfoMap();
     }
+    if (hint_created_) {
+      for (auto iter : GetHintMap()) {
+        delete[] reinterpret_cast<char*>(iter.second);
+      }
+      reinterpret_cast<HintMap*>(&hint_)->~HintMap();
+    }
     delete rebuilding_trx_;
   }
 
@@ -1404,7 +1429,8 @@ class MemTableInserter : public WriteBatch::Handler {
     if (!moptions->inplace_update_support) {
       bool mem_res =
           mem->Add(sequence_, value_type, key, value,
-                   concurrent_memtable_writes_, get_post_process_info(mem));
+                   concurrent_memtable_writes_, get_post_process_info(mem),
+                   hint_per_batch_ ? &GetHintMap()[mem] : nullptr);
       if (UNLIKELY(!mem_res)) {
         assert(seq_per_batch_);
         ret_status = Status::TryAgain("key+seq exists");
@@ -1487,7 +1513,8 @@ class MemTableInserter : public WriteBatch::Handler {
     MemTable* mem = cf_mems_->GetMemTable();
     bool mem_res =
         mem->Add(sequence_, delete_type, key, value,
-                 concurrent_memtable_writes_, get_post_process_info(mem));
+                 concurrent_memtable_writes_, get_post_process_info(mem),
+                 hint_per_batch_ ? &GetHintMap()[mem] : nullptr);
     if (UNLIKELY(!mem_res)) {
       assert(seq_per_batch_);
       ret_status = Status::TryAgain("key+seq exists");
@@ -1962,7 +1989,7 @@ Status WriteBatchInternal::InsertInto(
     TrimHistoryScheduler* trim_history_scheduler,
     bool ignore_missing_column_families, uint64_t log_number, DB* db,
     bool concurrent_memtable_writes, bool seq_per_batch, size_t batch_cnt,
-    bool batch_per_txn) {
+    bool batch_per_txn, bool hint_per_batch) {
 #ifdef NDEBUG
   (void)batch_cnt;
 #endif
@@ -1971,7 +1998,7 @@ Status WriteBatchInternal::InsertInto(
       sequence, memtables, flush_scheduler, trim_history_scheduler,
       ignore_missing_column_families, log_number, db,
       concurrent_memtable_writes, nullptr /*has_valid_writes*/, seq_per_batch,
-      batch_per_txn);
+      batch_per_txn, hint_per_batch);
   SetSequence(writer->batch, sequence);
   inserter.set_log_number_ref(writer->log_ref);
   Status s = writer->batch->Iterate(&inserter);

db/write_batch_internal.h

@@ -188,7 +188,8 @@ class WriteBatchInternal {
                            uint64_t log_number = 0, DB* db = nullptr,
                            bool concurrent_memtable_writes = false,
                            bool seq_per_batch = false, size_t batch_cnt = 0,
-                           bool batch_per_txn = true);
+                           bool batch_per_txn = true,
+                           bool hint_per_batch = false);
 
   static Status Append(WriteBatch* dst, const WriteBatch* src,
                        const bool WAL_only = false);

include/rocksdb/c.h

@@ -1263,6 +1263,9 @@ extern ROCKSDB_LIBRARY_API void rocksdb_writeoptions_set_no_slowdown(
     rocksdb_writeoptions_t*, unsigned char);
 extern ROCKSDB_LIBRARY_API void rocksdb_writeoptions_set_low_pri(
     rocksdb_writeoptions_t*, unsigned char);
+extern ROCKSDB_LIBRARY_API void
+rocksdb_writeoptions_set_memtable_insert_hint_per_batch(rocksdb_writeoptions_t*,
+                                                        unsigned char);
 
 /* Compact range options */
 

include/rocksdb/memtablerep.h

@@ -120,6 +120,28 @@ class MemTableRep {
     return true;
   }
 
+  // Same as ::InsertWithHint, but allow concurrnet write
+  //
+  // If hint points to nullptr, a new hint will be allocated on heap, otherwise
+  // the hint will be updated to reflect the last insert location. The hint is
+  // owned by the caller and it is the caller's responsibility to delete the
+  // hint later.
+  //
+  // Currently only skip-list based memtable implement the interface. Other
+  // implementations will fallback to InsertConcurrently() by default.
+  virtual void InsertWithHintConcurrently(KeyHandle handle, void** /*hint*/) {
+    // Ignore the hint by default.
+    InsertConcurrently(handle);
+  }
+
+  // Same as ::InsertWithHintConcurrently
+  // Returns false if MemTableRepFactory::CanHandleDuplicatedKey() is true and
+  // the <key, seq> already exists.
+  virtual bool InsertKeyWithHintConcurrently(KeyHandle handle, void** hint) {
+    InsertWithHintConcurrently(handle, hint);
+    return true;
+  }
+
   // Like Insert(handle), but may be called concurrent with other calls
   // to InsertConcurrently for other handles.
   //

include/rocksdb/options.h

@@ -1356,6 +1356,15 @@ struct WriteOptions {
   // Default: false
   bool low_pri;
 
+  // If true, this writebatch will maintain the last insert positions of each
+  // memtable as hints in concurrent write. It can improve write performance
+  // in concurrent writes if keys in one writebatch are sequential. In
+  // non-concurrent writes (when concurrent_memtable_writes is false) this
+  // option will be ignored.
+  //
+  // Default: false
+  bool memtable_insert_hint_per_batch;
+
   // Timestamp of write operation, e.g. Put. All timestamps of the same
   // database must share the same length and format. The user is also
   // responsible for providing a customized compare function via Comparator to
@@ -1373,6 +1382,7 @@ struct WriteOptions {
         ignore_missing_column_families(false),
         no_slowdown(false),
         low_pri(false),
+        memtable_insert_hint_per_batch(false),
         timestamp(nullptr) {}
 };
 

memtable/inlineskiplist.h

@@ -86,6 +86,9 @@ class InlineSkipList {
   // Allocate a splice using allocator.
   Splice* AllocateSplice();
 
+  // Allocate a splice on heap.
+  Splice* AllocateSpliceOnHeap();
+
   // Inserts a key allocated by AllocateKey, after the actual key value
   // has been filled in.
   //
@@ -105,6 +108,12 @@ class InlineSkipList {
   // REQUIRES: no concurrent calls to any of inserts.
   bool InsertWithHint(const char* key, void** hint);
 
+  // Like InsertConcurrently, but with a hint
+  //
+  // REQUIRES: nothing that compares equal to key is currently in the list.
+  // REQUIRES: no concurrent calls that use same hint
+  bool InsertWithHintConcurrently(const char* key, void** hint);
+
   // Like Insert, but external synchronization is not required.
   bool InsertConcurrently(const char* key);
 
@@ -642,6 +651,18 @@ InlineSkipList<Comparator>::AllocateSplice() {
   return splice;
 }
 
+template <class Comparator>
+typename InlineSkipList<Comparator>::Splice*
+InlineSkipList<Comparator>::AllocateSpliceOnHeap() {
+  size_t array_size = sizeof(Node*) * (kMaxHeight_ + 1);
+  char* raw = new char[sizeof(Splice) + array_size * 2];
+  Splice* splice = reinterpret_cast<Splice*>(raw);
+  splice->height_ = 0;
+  splice->prev_ = reinterpret_cast<Node**>(raw + sizeof(Splice));
+  splice->next_ = reinterpret_cast<Node**>(raw + sizeof(Splice) + array_size);
+  return splice;
+}
+
 template <class Comparator>
 bool InlineSkipList<Comparator>::Insert(const char* key) {
   return Insert<false>(key, seq_splice_, false);
@@ -668,6 +689,18 @@ bool InlineSkipList<Comparator>::InsertWithHint(const char* key, void** hint) {
   return Insert<false>(key, splice, true);
 }
 
+template <class Comparator>
+bool InlineSkipList<Comparator>::InsertWithHintConcurrently(const char* key,
+                                                            void** hint) {
+  assert(hint != nullptr);
+  Splice* splice = reinterpret_cast<Splice*>(*hint);
+  if (splice == nullptr) {
+    splice = AllocateSpliceOnHeap();
+    *hint = reinterpret_cast<void*>(splice);
+  }
+  return Insert<true>(key, splice, true);
+}
+
 template <class Comparator>
 template <bool prefetch_before>
 void InlineSkipList<Comparator>::FindSpliceForLevel(const DecodedKey& key,