Add a new per level counter for block cache hit (#4796)

Summary:
Add a new per level counter for block cache hits, increase it by one on every successful attempt to get an entry from cache.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4796

Differential Revision: D13513688

Pulled By: zinoale

fbshipit-source-id: 104df038f1232e3356e162eb2d8ca138e34a8281

db/perf_context_test.cc

@@ -696,6 +696,10 @@ TEST_F(PerfContextTest, PerfContextByLevelGetSet) {
   PERF_COUNTER_BY_LEVEL_ADD(bloom_filter_useful, 1, 7);
   PERF_COUNTER_BY_LEVEL_ADD(bloom_filter_useful, 1, 7);
   PERF_COUNTER_BY_LEVEL_ADD(bloom_filter_full_true_positive, 1, 2);
+  PERF_COUNTER_BY_LEVEL_ADD(block_cache_hit_count, 1, 0);
+  PERF_COUNTER_BY_LEVEL_ADD(block_cache_hit_count, 5, 2);
+  PERF_COUNTER_BY_LEVEL_ADD(block_cache_miss_count, 2, 3);
+  PERF_COUNTER_BY_LEVEL_ADD(block_cache_miss_count, 4, 1);
   ASSERT_EQ(
       0, (*(get_perf_context()->level_to_perf_context))[0].bloom_filter_useful);
   ASSERT_EQ(
@@ -706,6 +710,14 @@ TEST_F(PerfContextTest, PerfContextByLevelGetSet) {
                    .bloom_filter_full_positive);
   ASSERT_EQ(1, (*(get_perf_context()->level_to_perf_context))[2]
                    .bloom_filter_full_true_positive);
+  ASSERT_EQ(1, (*(get_perf_context()->level_to_perf_context))[0]
+                  .block_cache_hit_count);
+  ASSERT_EQ(5, (*(get_perf_context()->level_to_perf_context))[2]
+                  .block_cache_hit_count);
+  ASSERT_EQ(2, (*(get_perf_context()->level_to_perf_context))[3]
+                  .block_cache_miss_count);
+  ASSERT_EQ(4, (*(get_perf_context()->level_to_perf_context))[1]
+                  .block_cache_miss_count);
   std::string zero_excluded = get_perf_context()->ToString(true);
   ASSERT_NE(std::string::npos,
             zero_excluded.find("bloom_filter_useful = 1@level5, 2@level7"));
@@ -713,6 +725,10 @@ TEST_F(PerfContextTest, PerfContextByLevelGetSet) {
             zero_excluded.find("bloom_filter_full_positive = 1@level0"));
   ASSERT_NE(std::string::npos,
             zero_excluded.find("bloom_filter_full_true_positive = 1@level2"));
+  ASSERT_NE(std::string::npos,
+            zero_excluded.find("block_cache_hit_count = 1@level0, 5@level2"));
+  ASSERT_NE(std::string::npos,
+            zero_excluded.find("block_cache_miss_count = 4@level1, 2@level3"));
 }
 }  // namespace rocksdb
 

include/rocksdb/perf_context.h

@@ -35,6 +35,9 @@ struct PerfContextByLevel {
   // total nanos spent on reading data from SST files
   uint64_t get_from_table_nanos;
 
+  uint64_t block_cache_hit_count = 0;     // total number of block cache hits
+  uint64_t block_cache_miss_count = 0;    // total number of block cache misses
+
   void Reset(); // reset all performance counters to zero
 };
 

monitoring/perf_context.cc

@@ -144,6 +144,8 @@ void PerfContextByLevel::Reset() {
   bloom_filter_useful = 0;
   bloom_filter_full_positive = 0;
   bloom_filter_full_true_positive = 0;
+  block_cache_hit_count = 0;
+  block_cache_miss_count = 0;
 #endif
 }
 
@@ -229,6 +231,8 @@ std::string PerfContext::ToString(bool exclude_zero_counters) const {
   PERF_CONTEXT_BY_LEVEL_OUTPUT_ONE_COUNTER(bloom_filter_useful);
   PERF_CONTEXT_BY_LEVEL_OUTPUT_ONE_COUNTER(bloom_filter_full_positive);
   PERF_CONTEXT_BY_LEVEL_OUTPUT_ONE_COUNTER(bloom_filter_full_true_positive);
+  PERF_CONTEXT_BY_LEVEL_OUTPUT_ONE_COUNTER(block_cache_hit_count);
+  PERF_CONTEXT_BY_LEVEL_OUTPUT_ONE_COUNTER(block_cache_miss_count);
   return ss.str();
 #endif
 }

table/block_based_table_reader.cc

@@ -151,6 +151,7 @@ Slice GetCacheKeyFromOffset(const char* cache_key_prefix,
 }
 
 Cache::Handle* GetEntryFromCache(Cache* block_cache, const Slice& key,
+                                 int level,
                                  Tickers block_cache_miss_ticker,
                                  Tickers block_cache_hit_ticker,
                                  uint64_t* block_cache_miss_stats,
@@ -160,6 +161,8 @@ Cache::Handle* GetEntryFromCache(Cache* block_cache, const Slice& key,
   auto cache_handle = block_cache->Lookup(key, statistics);
   if (cache_handle != nullptr) {
     PERF_COUNTER_ADD(block_cache_hit_count, 1);
+    PERF_COUNTER_BY_LEVEL_ADD(block_cache_hit_count, 1,
+      static_cast<uint32_t>(level));
     if (get_context != nullptr) {
       // overall cache hit
       get_context->get_context_stats_.num_cache_hit++;
@@ -177,6 +180,8 @@ Cache::Handle* GetEntryFromCache(Cache* block_cache, const Slice& key,
       RecordTick(statistics, block_cache_hit_ticker);
     }
   } else {
+    PERF_COUNTER_BY_LEVEL_ADD(block_cache_miss_count, 1,
+      static_cast<uint32_t>(level));
     if (get_context != nullptr) {
       // overall cache miss
       get_context->get_context_stats_.num_cache_miss++;
@@ -1284,7 +1289,7 @@ Status BlockBasedTable::GetDataBlockFromCache(
   // Lookup uncompressed cache first
   if (block_cache != nullptr) {
     block->cache_handle = GetEntryFromCache(
-        block_cache, block_cache_key,
+        block_cache, block_cache_key, rep->level,
         is_index ? BLOCK_CACHE_INDEX_MISS : BLOCK_CACHE_DATA_MISS,
         is_index ? BLOCK_CACHE_INDEX_HIT : BLOCK_CACHE_DATA_HIT,
         get_context
@@ -1613,7 +1618,8 @@ BlockBasedTable::CachableEntry<FilterBlockReader> BlockBasedTable::GetFilter(
 
   Statistics* statistics = rep_->ioptions.statistics;
   auto cache_handle = GetEntryFromCache(
-      block_cache, key, BLOCK_CACHE_FILTER_MISS, BLOCK_CACHE_FILTER_HIT,
+      block_cache, key, rep_->level,
+      BLOCK_CACHE_FILTER_MISS, BLOCK_CACHE_FILTER_HIT,
       get_context ? &get_context->get_context_stats_.num_cache_filter_miss
                   : nullptr,
       get_context ? &get_context->get_context_stats_.num_cache_filter_hit
@@ -1696,7 +1702,8 @@ InternalIteratorBase<BlockHandle>* BlockBasedTable::NewIndexIterator(
                             rep_->dummy_index_reader_offset, cache_key);
   Statistics* statistics = rep_->ioptions.statistics;
   auto cache_handle = GetEntryFromCache(
-      block_cache, key, BLOCK_CACHE_INDEX_MISS, BLOCK_CACHE_INDEX_HIT,
+      block_cache, key, rep_->level,
+      BLOCK_CACHE_INDEX_MISS, BLOCK_CACHE_INDEX_HIT,
       get_context ? &get_context->get_context_stats_.num_cache_index_miss
                   : nullptr,
       get_context ? &get_context->get_context_stats_.num_cache_index_hit