Avoid dynamic memory allocation on read path (#10453)

Summary:
lambda function dynamicly allocates memory from heap if it needs to
capture multiple values, which could be expensive.
Switch to explictly use local functor from stack.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10453

Test Plan:
CI
db_bench shows ~2-3% read improvement:
```
# before the change
TEST_TMPDIR=/tmp/dbbench4 ./db_bench_main --benchmarks=filluniquerandom,readrandom -compression_type=none -max_background_jobs=12 -num=10000000
readrandom   :       8.528 micros/op 117265 ops/sec 85.277 seconds 10000000 operations;   13.0 MB/s (10000000 of 10000000 found)
# after the change
TEST_TMPDIR=/tmp/dbbench5 ./db_bench_new --benchmarks=filluniquerandom,readrandom -compression_type=none -max_background_jobs=12 -num=10000000
readrandom   :       8.263 micros/op 121015 ops/sec 82.634 seconds 10000000 operations;   13.4 MB/s (10000000 of 10000000 found)
```
details: https://gist.github.com/jay-zhuang/5ac0628db8fc9cbcb499e056d4cb5918

Micro-benchmark shows a similar improvement ~1-2%:
before the change:
https://gist.github.com/jay-zhuang/9dc0ebf51bbfbf4af82f6193d43cf75b
after the change:
https://gist.github.com/jay-zhuang/fc061f1813cd8f441109ad0b0fe7c185

Reviewed By: ajkr

Differential Revision: D38345056

Pulled By: jay-zhuang

fbshipit-source-id: f3597aeeee338a804d37bf2e81386d5a100665e0

HISTORY.md

@@ -30,6 +30,7 @@
 
 ### Performance Improvements
 * Instead of constructing `FragmentedRangeTombstoneList` during every read operation, it is now constructed once and stored in immutable memtables. This improves speed of querying range tombstones from immutable memtables.  
+* Improve read performance by avoiding dynamic memory allocation.
 
 ## 7.5.0 (07/15/2022)
 ### New Features

table/block_based/block_based_table_reader.cc

@@ -1253,8 +1253,12 @@ Status BlockBasedTable::GetDataBlockFromCache(
   Statistics* statistics = rep_->ioptions.statistics.get();
   bool using_zstd = rep_->blocks_definitely_zstd_compressed;
   const FilterPolicy* filter_policy = rep_->filter_policy;
-  Cache::CreateCallback create_cb = GetCreateCallback<TBlocklike>(
+  CacheCreateCallback<TBlocklike> callback(read_amp_bytes_per_bit, statistics,
-      read_amp_bytes_per_bit, statistics, using_zstd, filter_policy);
+                                           using_zstd, filter_policy);
+  // avoid dynamic memory allocation by using the reference (std::ref) of the
+  // callback. Otherwise, binding a functor to std::function will allocate extra
+  // memory from heap.
+  Cache::CreateCallback create_cb(std::ref(callback));
 
   // Lookup uncompressed cache first
   if (block_cache != nullptr) {
@@ -1284,8 +1288,11 @@ Status BlockBasedTable::GetDataBlockFromCache(
   BlockContents contents;
   if (rep_->ioptions.lowest_used_cache_tier ==
       CacheTier::kNonVolatileBlockTier) {
-    Cache::CreateCallback create_cb_special = GetCreateCallback<BlockContents>(
+    CacheCreateCallback<BlockContents> special_callback(
         read_amp_bytes_per_bit, statistics, using_zstd, filter_policy);
+    // avoid dynamic memory allocation by using the reference (std::ref) of the
+    // callback. Make sure the callback is only used within this code block.
+    Cache::CreateCallback create_cb_special(std::ref(special_callback));
     block_cache_compressed_handle = block_cache_compressed->Lookup(
         cache_key,
         BlocklikeTraits<BlockContents>::GetCacheItemHelper(block_type),

table/block_based/block_like_traits.h

@@ -21,24 +21,42 @@ template <typename T, CacheEntryRole R>
 Cache::CacheItemHelper* GetCacheItemHelperForRole();
 
 template <typename TBlocklike>
-Cache::CreateCallback GetCreateCallback(size_t read_amp_bytes_per_bit,
+class CacheCreateCallback {
+ public:
+  CacheCreateCallback() = delete;
+  CacheCreateCallback(const CacheCreateCallback&) = delete;
+  CacheCreateCallback(CacheCreateCallback&&) = delete;
+  CacheCreateCallback& operator=(const CacheCreateCallback&) = delete;
+  CacheCreateCallback& operator=(CacheCreateCallback&&) = delete;
+
+  explicit CacheCreateCallback(size_t read_amp_bytes_per_bit,
                                Statistics* statistics, bool using_zstd,
-                                        const FilterPolicy* filter_policy) {
+                               const FilterPolicy* filter_policy)
-  return [read_amp_bytes_per_bit, statistics, using_zstd, filter_policy](
+      : read_amp_bytes_per_bit_(read_amp_bytes_per_bit),
-             const void* buf, size_t size, void** out_obj,
+        statistics_(statistics),
-             size_t* charge) -> Status {
+        using_zstd_(using_zstd),
+        filter_policy_(filter_policy) {}
+
+  Status operator()(const void* buf, size_t size, void** out_obj,
+                    size_t* charge) {
     assert(buf != nullptr);
     std::unique_ptr<char[]> buf_data(new char[size]());
     memcpy(buf_data.get(), buf, size);
     BlockContents bc = BlockContents(std::move(buf_data), size);
     TBlocklike* ucd_ptr = BlocklikeTraits<TBlocklike>::Create(
-        std::move(bc), read_amp_bytes_per_bit, statistics, using_zstd,
+        std::move(bc), read_amp_bytes_per_bit_, statistics_, using_zstd_,
-        filter_policy);
+        filter_policy_);
     *out_obj = reinterpret_cast<void*>(ucd_ptr);
     *charge = size;
     return Status::OK();
-  };
+  }
-}
+
+ private:
+  const size_t read_amp_bytes_per_bit_;
+  Statistics* statistics_;
+  const bool using_zstd_;
+  const FilterPolicy* filter_policy_;
+};
 
 template <>
 class BlocklikeTraits<BlockContents> {