draft

Author: hx235

HISTORY.md

@@ -8,6 +8,7 @@
 
 ### New Features
 * Add statistics rocksdb.secondary.cache.filter.hits, rocksdb.secondary.cache.index.hits, and rocksdb.secondary.cache.filter.hits
+* Add new stat rocksdb.table.prefetch.tail.read.bytes to report number of bytes read in prefetching contents from the end of SST tables during table open
 
 ## 8.0.0 (02/19/2023)
 ### Behavior changes

include/rocksdb/statistics.h

@@ -533,6 +533,10 @@ enum Histograms : uint32_t {
   // Wait time for aborting async read in FilePrefetchBuffer destructor
   ASYNC_PREFETCH_ABORT_MICROS,
 
+  // Number of bytes read in prefetching contents from the end of SST tables
+  // during table open
+  TABLE_PREFETCH_TAIL_READ_BYTES,
+
   HISTOGRAM_ENUM_MAX
 };
 

java/rocksjni/portal.h

@@ -5609,6 +5609,8 @@ class HistogramTypeJni {
         return 0x37;
       case ASYNC_PREFETCH_ABORT_MICROS:
         return 0x38;
+      case ROCKSDB_NAMESPACE::Histograms::TABLE_PREFETCH_TAIL_READ_BYTES:
+        return 0x39;
       case ROCKSDB_NAMESPACE::Histograms::HISTOGRAM_ENUM_MAX:
         // 0x1F for backwards compatibility on current minor version.
         return 0x1F;
@@ -5725,6 +5727,8 @@ class HistogramTypeJni {
         return ROCKSDB_NAMESPACE::Histograms::NUM_LEVEL_READ_PER_MULTIGET;
       case 0x38:
         return ROCKSDB_NAMESPACE::Histograms::ASYNC_PREFETCH_ABORT_MICROS;
+      case 0x39:
+        return ROCKSDB_NAMESPACE::Histograms::TABLE_PREFETCH_TAIL_READ_BYTES;
       case 0x1F:
         // 0x1F for backwards compatibility on current minor version.
         return ROCKSDB_NAMESPACE::Histograms::HISTOGRAM_ENUM_MAX;

java/src/main/java/org/rocksdb/HistogramType.java

@@ -162,6 +162,8 @@ public enum HistogramType {
 
   ASYNC_READ_BYTES((byte) 0x33),
 
+  TABLE_PREFETCH_TAIL_READ_BYTES((byte) 0x39),
+
   // 0x1F for backwards compatibility on current minor version.
   HISTOGRAM_ENUM_MAX((byte) 0x1F);
 

monitoring/statistics.cc

@@ -272,6 +272,7 @@ const std::vector<std::pair<Histograms, std::string>> HistogramsNameMap = {
     {MULTIGET_IO_BATCH_SIZE, "rocksdb.multiget.io.batch.size"},
     {NUM_LEVEL_READ_PER_MULTIGET, "rocksdb.num.level.read.per.multiget"},
     {ASYNC_PREFETCH_ABORT_MICROS, "rocksdb.async.prefetch.abort.micros"},
+    {TABLE_PREFETCH_TAIL_READ_BYTES, "rocksdb.table.prefetch.tail.read.bytes"},
 };
 
 std::shared_ptr<Statistics> CreateDBStatistics() {

table/block_based/block_based_table_reader.cc

@@ -591,7 +591,7 @@ Status BlockBasedTable::Open(
   if (!ioptions.allow_mmap_reads) {
     s = PrefetchTail(ro, file.get(), file_size, force_direct_prefetch,
                      tail_prefetch_stats, prefetch_all, preload_all,
-                     &prefetch_buffer);
+                     &prefetch_buffer, ioptions.stats);
     // Return error in prefetch path to users.
     if (!s.ok()) {
       return s;
@@ -802,7 +802,7 @@ Status BlockBasedTable::PrefetchTail(
     const ReadOptions& ro, RandomAccessFileReader* file, uint64_t file_size,
     bool force_direct_prefetch, TailPrefetchStats* tail_prefetch_stats,
     const bool prefetch_all, const bool preload_all,
-    std::unique_ptr<FilePrefetchBuffer>* prefetch_buffer) {
+    std::unique_ptr<FilePrefetchBuffer>* prefetch_buffer, Statistics* stats) {
   size_t tail_prefetch_size = 0;
   if (tail_prefetch_stats != nullptr) {
     // Multiple threads may get a 0 (no history) when running in parallel,
@@ -852,6 +852,7 @@ Status BlockBasedTable::PrefetchTail(
     s = (*prefetch_buffer)
             ->Prefetch(opts, file, prefetch_off, prefetch_len,
                        ro.rate_limiter_priority);
+    RecordInHistogram(stats, TABLE_PREFETCH_TAIL_READ_BYTES, prefetch_len);
   }
   return s;
 }

table/block_based/block_based_table_reader.h

@@ -444,7 +444,7 @@ class BlockBasedTable : public TableReader {
       const ReadOptions& ro, RandomAccessFileReader* file, uint64_t file_size,
       bool force_direct_prefetch, TailPrefetchStats* tail_prefetch_stats,
       const bool prefetch_all, const bool preload_all,
-      std::unique_ptr<FilePrefetchBuffer>* prefetch_buffer);
+      std::unique_ptr<FilePrefetchBuffer>* prefetch_buffer, Statistics* stats);
   Status ReadMetaIndexBlock(const ReadOptions& ro,
                             FilePrefetchBuffer* prefetch_buffer,
                             std::unique_ptr<Block>* metaindex_block,