Add rate limiter priority to ReadOptions (#9424)

Summary:
Users can set the priority for file reads associated with their operation by setting `ReadOptions::rate_limiter_priority` to something other than `Env::IO_TOTAL`. Rate limiting `VerifyChecksum()` and `VerifyFileChecksums()` is the motivation for this PR, so it also includes benchmarks and minor bug fixes to get that working.

`RandomAccessFileReader::Read()` already had support for rate limiting compaction reads. I changed that rate limiting to be non-specific to compaction, but rather performed according to the passed in `Env::IOPriority`. Now the compaction read rate limiting is supported by setting `rate_limiter_priority = Env::IO_LOW` on its `ReadOptions`.

There is no default value for the new `Env::IOPriority` parameter to `RandomAccessFileReader::Read()`. That means this PR goes through all callers (in some cases multiple layers up the call stack) to find a `ReadOptions` to provide the priority. There are TODOs for cases I believe it would be good to let user control the priority some day (e.g., file footer reads), and no TODO in cases I believe it doesn't matter (e.g., trace file reads).

The API doc only lists the missing cases where a file read associated with a provided `ReadOptions` cannot be rate limited. For cases like file ingestion checksum calculation, there is no API to provide `ReadOptions` or `Env::IOPriority`, so I didn't count that as missing.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9424

Test Plan:
- new unit tests
- new benchmarks on ~50MB database with 1MB/s read rate limit and 100ms refill interval; verified with strace reads are chunked (at 0.1MB per chunk) and spaced roughly 100ms apart.
  - setup command: `./db_bench -benchmarks=fillrandom,compact -db=/tmp/testdb -target_file_size_base=1048576 -disable_auto_compactions=true -file_checksum=true`
  - benchmarks command: `strace -ttfe pread64 ./db_bench -benchmarks=verifychecksum,verifyfilechecksums -use_existing_db=true -db=/tmp/testdb -rate_limiter_bytes_per_sec=1048576 -rate_limit_bg_reads=1 -rate_limit_user_ops=true -file_checksum=true`
- crash test using IO_USER priority on non-validation reads with https://github.com/facebook/rocksdb/issues/9567 reverted: `python3 tools/db_crashtest.py blackbox --max_key=1000000 --write_buffer_size=524288 --target_file_size_base=524288 --level_compaction_dynamic_level_bytes=true --duration=3600 --rate_limit_bg_reads=true --rate_limit_user_ops=true --rate_limiter_bytes_per_sec=10485760 --interval=10`

Reviewed By: hx235

Differential Revision: D33747386

Pulled By: ajkr

fbshipit-source-id: a2d985e97912fba8c54763798e04f006ccc56e0c

CMakeLists.txt

@@ -1196,6 +1196,7 @@ if(WITH_TESTS)
         db/db_options_test.cc
         db/db_properties_test.cc
         db/db_range_del_test.cc
+        db/db_rate_limiter_test.cc
         db/db_secondary_test.cc
         db/db_sst_test.cc
         db/db_statistics_test.cc

HISTORY.md

@@ -13,6 +13,7 @@
 
 ### Public API changes
 * Require C++17 compatible compiler (GCC >= 7, Clang >= 5, Visual Studio >= 2017). See #9388.
+* Added `ReadOptions::rate_limiter_priority`. When set to something other than `Env::IO_TOTAL`, the internal rate limiter (`DBOptions::rate_limiter`) will be charged at the specified priority for file reads associated with the API to which the `ReadOptions` was provided.
 * Remove HDFS support from main repo.
 * Remove librados support from main repo.
 * Remove obsolete backupable_db.h and type alias `BackupableDBOptions`. Use backup_engine.h and `BackupEngineOptions`. Similar renamings are in the C and Java APIs.

Makefile

@@ -1533,6 +1533,9 @@ db_options_test: $(OBJ_DIR)/db/db_options_test.o $(TEST_LIBRARY) $(LIBRARY)
 db_range_del_test: $(OBJ_DIR)/db/db_range_del_test.o $(TEST_LIBRARY) $(LIBRARY)
 	$(AM_LINK)
 
+db_rate_limiter_test: $(OBJ_DIR)/db/db_rate_limiter_test.o $(TEST_LIBRARY) $(LIBRARY)
+	$(AM_LINK)
+
 db_sst_test: $(OBJ_DIR)/db/db_sst_test.o $(TEST_LIBRARY) $(LIBRARY)
 	$(AM_LINK)
 

TARGETS

@@ -1441,6 +1441,13 @@ ROCKS_TESTS = [
         [],
         [],
     ],
+    [
+        "db_rate_limiter_test",
+        "db/db_rate_limiter_test.cc",
+        "parallel",
+        [],
+        [],
+    ],
     [
         "db_secondary_test",
         "db/db_secondary_test.cc",

db/blob/blob_file_reader.cc

@@ -148,9 +148,10 @@ Status BlobFileReader::ReadHeader(const RandomAccessFileReader* file_reader,
     constexpr uint64_t read_offset = 0;
     constexpr size_t read_size = BlobLogHeader::kSize;
 
-    const Status s =
+    // TODO: rate limit reading headers from blob files.
-        ReadFromFile(file_reader, read_offset, read_size, statistics,
+    const Status s = ReadFromFile(file_reader, read_offset, read_size,
-                     &header_slice, &buf, &aligned_buf);
+                                  statistics, &header_slice, &buf, &aligned_buf,
+                                  Env::IO_TOTAL /* rate_limiter_priority */);
     if (!s.ok()) {
       return s;
     }
@@ -198,9 +199,10 @@ Status BlobFileReader::ReadFooter(const RandomAccessFileReader* file_reader,
     const uint64_t read_offset = file_size - BlobLogFooter::kSize;
     constexpr size_t read_size = BlobLogFooter::kSize;
 
-    const Status s =
+    // TODO: rate limit reading footers from blob files.
-        ReadFromFile(file_reader, read_offset, read_size, statistics,
+    const Status s = ReadFromFile(file_reader, read_offset, read_size,
-                     &footer_slice, &buf, &aligned_buf);
+                                  statistics, &footer_slice, &buf, &aligned_buf,
+                                  Env::IO_TOTAL /* rate_limiter_priority */);
     if (!s.ok()) {
       return s;
     }
@@ -230,7 +232,8 @@ Status BlobFileReader::ReadFooter(const RandomAccessFileReader* file_reader,
 Status BlobFileReader::ReadFromFile(const RandomAccessFileReader* file_reader,
                                     uint64_t read_offset, size_t read_size,
                                     Statistics* statistics, Slice* slice,
-                                    Buffer* buf, AlignedBuf* aligned_buf) {
+                                    Buffer* buf, AlignedBuf* aligned_buf,
+                                    Env::IOPriority rate_limiter_priority) {
   assert(slice);
   assert(buf);
   assert(aligned_buf);
@@ -245,13 +248,13 @@ Status BlobFileReader::ReadFromFile(const RandomAccessFileReader* file_reader,
     constexpr char* scratch = nullptr;
 
     s = file_reader->Read(IOOptions(), read_offset, read_size, slice, scratch,
-                          aligned_buf);
+                          aligned_buf, rate_limiter_priority);
   } else {
     buf->reset(new char[read_size]);
     constexpr AlignedBuf* aligned_scratch = nullptr;
 
     s = file_reader->Read(IOOptions(), read_offset, read_size, slice,
-                          buf->get(), aligned_scratch);
+                          buf->get(), aligned_scratch, rate_limiter_priority);
   }
 
   if (!s.ok()) {
@@ -323,7 +326,8 @@ Status BlobFileReader::GetBlob(const ReadOptions& read_options,
 
     prefetched = prefetch_buffer->TryReadFromCache(
         IOOptions(), file_reader_.get(), record_offset,
-        static_cast<size_t>(record_size), &record_slice, &s, for_compaction);
+        static_cast<size_t>(record_size), &record_slice, &s,
+        read_options.rate_limiter_priority, for_compaction);
     if (!s.ok()) {
       return s;
     }
@@ -334,7 +338,8 @@ Status BlobFileReader::GetBlob(const ReadOptions& read_options,
 
     const Status s = ReadFromFile(file_reader_.get(), record_offset,
                                   static_cast<size_t>(record_size), statistics_,
-                                  &record_slice, &buf, &aligned_buf);
+                                  &record_slice, &buf, &aligned_buf,
+                                  read_options.rate_limiter_priority);
     if (!s.ok()) {
       return s;
     }
@@ -424,7 +429,8 @@ void BlobFileReader::MultiGetBlob(
   }
   TEST_SYNC_POINT("BlobFileReader::MultiGetBlob:ReadFromFile");
   s = file_reader_->MultiRead(IOOptions(), read_reqs.data(), read_reqs.size(),
-                              direct_io ? &aligned_buf : nullptr);
+                              direct_io ? &aligned_buf : nullptr,
+                              read_options.rate_limiter_priority);
   if (!s.ok()) {
     for (auto& req : read_reqs) {
       req.status.PermitUncheckedError();

db/blob/blob_file_reader.h

@@ -83,7 +83,8 @@ class BlobFileReader {
   static Status ReadFromFile(const RandomAccessFileReader* file_reader,
                              uint64_t read_offset, size_t read_size,
                              Statistics* statistics, Slice* slice, Buffer* buf,
-                             AlignedBuf* aligned_buf);
+                             AlignedBuf* aligned_buf,
+                             Env::IOPriority rate_limiter_priority);
 
   static Status VerifyBlob(const Slice& record_slice, const Slice& user_key,
                            uint64_t value_size);

db/blob/blob_log_sequential_reader.cc

@@ -28,8 +28,10 @@ Status BlobLogSequentialReader::ReadSlice(uint64_t size, Slice* slice,
   assert(file_);
 
   StopWatch read_sw(clock_, statistics_, BLOB_DB_BLOB_FILE_READ_MICROS);
-  Status s = file_->Read(IOOptions(), next_byte_, static_cast<size_t>(size),
+  // TODO: rate limit `BlobLogSequentialReader` reads (it appears unused?)
-                         slice, buf, nullptr);
+  Status s =
+      file_->Read(IOOptions(), next_byte_, static_cast<size_t>(size), slice,
+                  buf, nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
   next_byte_ += size;
   if (!s.ok()) {
     return s;

db/compaction/compaction_job.cc

@@ -1264,6 +1264,7 @@ void CompactionJob::ProcessKeyValueCompaction(SubcompactionState* sub_compact) {
   ReadOptions read_options;
   read_options.verify_checksums = true;
   read_options.fill_cache = false;
+  read_options.rate_limiter_priority = Env::IO_LOW;
   // Compaction iterators shouldn't be confined to a single prefix.
   // Compactions use Seek() for
   // (a) concurrent compactions,

db/convenience.cc

@@ -56,7 +56,10 @@ Status VerifySstFileChecksum(const Options& options,
   }
   std::unique_ptr<TableReader> table_reader;
   std::unique_ptr<RandomAccessFileReader> file_reader(
-      new RandomAccessFileReader(std::move(file), file_path));
+      new RandomAccessFileReader(
+          std::move(file), file_path, ioptions.clock, nullptr /* io_tracer */,
+          nullptr /* stats */, 0 /* hist_type */, nullptr /* file_read_hist */,
+          ioptions.rate_limiter.get()));
   const bool kImmortal = true;
   s = ioptions.table_factory->NewTableReader(
       TableReaderOptions(ioptions, options.prefix_extractor, env_options,

db/db_impl/db_impl.cc

@@ -5175,7 +5175,8 @@ Status DBImpl::VerifyFullFileChecksum(const std::string& file_checksum_expected,
       fs_.get(), fname, immutable_db_options_.file_checksum_gen_factory.get(),
       func_name_expected, &file_checksum, &func_name,
       read_options.readahead_size, immutable_db_options_.allow_mmap_reads,
-      io_tracer_, immutable_db_options_.rate_limiter.get());
+      io_tracer_, immutable_db_options_.rate_limiter.get(),
+      read_options.rate_limiter_priority);
   if (s.ok()) {
     assert(func_name_expected == func_name);
     if (file_checksum != file_checksum_expected) {

db/db_rate_limiter_test.cc

@@ -0,0 +1,262 @@
+//  Copyright (c) 2022-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "db/db_test_util.h"
+#include "port/stack_trace.h"
+#include "util/file_checksum_helper.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class DBRateLimiterTest
+    : public DBTestBase,
+      public ::testing::WithParamInterface<std::tuple<bool, bool, bool>> {
+ public:
+  DBRateLimiterTest()
+      : DBTestBase("db_rate_limiter_test", /*env_do_fsync=*/false),
+        use_direct_io_(std::get<0>(GetParam())),
+        use_block_cache_(std::get<1>(GetParam())),
+        use_readahead_(std::get<2>(GetParam())) {}
+
+  void Init() {
+    options_ = GetOptions();
+    Reopen(options_);
+    for (int i = 0; i < kNumFiles; ++i) {
+      for (int j = 0; j < kNumKeysPerFile; ++j) {
+        ASSERT_OK(Put(Key(i * kNumKeysPerFile + j), "val"));
+      }
+      ASSERT_OK(Flush());
+    }
+    MoveFilesToLevel(1);
+  }
+
+  BlockBasedTableOptions GetTableOptions() {
+    BlockBasedTableOptions table_options;
+    table_options.no_block_cache = !use_block_cache_;
+    return table_options;
+  }
+
+  ReadOptions GetReadOptions() {
+    ReadOptions read_options;
+    read_options.rate_limiter_priority = Env::IO_USER;
+    read_options.readahead_size = use_readahead_ ? kReadaheadBytes : 0;
+    return read_options;
+  }
+
+  Options GetOptions() {
+    Options options = CurrentOptions();
+    options.disable_auto_compactions = true;
+    options.file_checksum_gen_factory.reset(new FileChecksumGenCrc32cFactory());
+    options.rate_limiter.reset(NewGenericRateLimiter(
+        1 << 20 /* rate_bytes_per_sec */, 100 * 1000 /* refill_period_us */,
+        10 /* fairness */, RateLimiter::Mode::kAllIo));
+    options.table_factory.reset(NewBlockBasedTableFactory(GetTableOptions()));
+    options.use_direct_reads = use_direct_io_;
+    return options;
+  }
+
+ protected:
+  const static int kNumKeysPerFile = 1;
+  const static int kNumFiles = 3;
+  const static int kReadaheadBytes = 32 << 10;  // 32KB
+
+  Options options_;
+  const bool use_direct_io_;
+  const bool use_block_cache_;
+  const bool use_readahead_;
+};
+
+std::string GetTestNameSuffix(
+    ::testing::TestParamInfo<std::tuple<bool, bool, bool>> info) {
+  std::ostringstream oss;
+  if (std::get<0>(info.param)) {
+    oss << "DirectIO";
+  } else {
+    oss << "BufferedIO";
+  }
+  if (std::get<1>(info.param)) {
+    oss << "_BlockCache";
+  } else {
+    oss << "_NoBlockCache";
+  }
+  if (std::get<2>(info.param)) {
+    oss << "_Readahead";
+  } else {
+    oss << "_NoReadahead";
+  }
+  return oss.str();
+}
+
+#ifndef ROCKSDB_LITE
+INSTANTIATE_TEST_CASE_P(DBRateLimiterTest, DBRateLimiterTest,
+                        ::testing::Combine(::testing::Bool(), ::testing::Bool(),
+                                           ::testing::Bool()),
+                        GetTestNameSuffix);
+#else   // ROCKSDB_LITE
+// Cannot use direct I/O in lite mode.
+INSTANTIATE_TEST_CASE_P(DBRateLimiterTest, DBRateLimiterTest,
+                        ::testing::Combine(::testing::Values(false),
+                                           ::testing::Bool(),
+                                           ::testing::Bool()),
+                        GetTestNameSuffix);
+#endif  // ROCKSDB_LITE
+
+TEST_P(DBRateLimiterTest, Get) {
+  if (use_direct_io_ && !IsDirectIOSupported()) {
+    return;
+  }
+  Init();
+
+  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+
+  int expected = 0;
+  for (int i = 0; i < kNumFiles; ++i) {
+    {
+      std::string value;
+      ASSERT_OK(db_->Get(GetReadOptions(), Key(i * kNumKeysPerFile), &value));
+      ++expected;
+    }
+    ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+
+    {
+      std::string value;
+      ASSERT_OK(db_->Get(GetReadOptions(), Key(i * kNumKeysPerFile), &value));
+      if (!use_block_cache_) {
+        ++expected;
+      }
+    }
+    ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+  }
+}
+
+TEST_P(DBRateLimiterTest, NewMultiGet) {
+  // The new void-returning `MultiGet()` APIs use `MultiRead()`, which does not
+  // yet support rate limiting.
+  if (use_direct_io_ && !IsDirectIOSupported()) {
+    return;
+  }
+  Init();
+
+  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+
+  const int kNumKeys = kNumFiles * kNumKeysPerFile;
+  {
+    std::vector<std::string> key_bufs;
+    key_bufs.reserve(kNumKeys);
+    std::vector<Slice> keys;
+    keys.reserve(kNumKeys);
+    for (int i = 0; i < kNumKeys; ++i) {
+      key_bufs.emplace_back(Key(i));
+      keys.emplace_back(key_bufs[i]);
+    }
+    std::vector<Status> statuses(kNumKeys);
+    std::vector<PinnableSlice> values(kNumKeys);
+    db_->MultiGet(GetReadOptions(), dbfull()->DefaultColumnFamily(), kNumKeys,
+                  keys.data(), values.data(), statuses.data());
+    for (int i = 0; i < kNumKeys; ++i) {
+      ASSERT_TRUE(statuses[i].IsNotSupported());
+    }
+  }
+  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+}
+
+TEST_P(DBRateLimiterTest, OldMultiGet) {
+  // The old `vector<Status>`-returning `MultiGet()` APIs use `Read()`, which
+  // supports rate limiting.
+  if (use_direct_io_ && !IsDirectIOSupported()) {
+    return;
+  }
+  Init();
+
+  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+
+  const int kNumKeys = kNumFiles * kNumKeysPerFile;
+  int expected = 0;
+  {
+    std::vector<std::string> key_bufs;
+    key_bufs.reserve(kNumKeys);
+    std::vector<Slice> keys;
+    keys.reserve(kNumKeys);
+    for (int i = 0; i < kNumKeys; ++i) {
+      key_bufs.emplace_back(Key(i));
+      keys.emplace_back(key_bufs[i]);
+    }
+    std::vector<std::string> values;
+    std::vector<Status> statuses =
+        db_->MultiGet(GetReadOptions(), keys, &values);
+    for (int i = 0; i < kNumKeys; ++i) {
+      ASSERT_OK(statuses[i]);
+    }
+  }
+  expected += kNumKeys;
+  ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+}
+
+TEST_P(DBRateLimiterTest, Iterator) {
+  if (use_direct_io_ && !IsDirectIOSupported()) {
+    return;
+  }
+  Init();
+
+  std::unique_ptr<Iterator> iter(db_->NewIterator(GetReadOptions()));
+  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+
+  int expected = 0;
+  for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+    ++expected;
+    ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+  }
+
+  for (iter->SeekToLast(); iter->Valid(); iter->Prev()) {
+    // When `use_block_cache_ == true`, the reverse scan will access the blocks
+    // loaded to cache during the above forward scan, in which case no further
+    // file reads are expected.
+    if (!use_block_cache_) {
+      ++expected;
+    }
+  }
+  // Reverse scan does not read evenly (one block per iteration) due to
+  // descending seqno ordering, so wait until after the loop to check total.
+  ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+}
+
+#if !defined(ROCKSDB_LITE)
+
+TEST_P(DBRateLimiterTest, VerifyChecksum) {
+  if (use_direct_io_ && !IsDirectIOSupported()) {
+    return;
+  }
+  Init();
+
+  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+
+  ASSERT_OK(db_->VerifyChecksum(GetReadOptions()));
+  // The files are tiny so there should have just been one read per file.
+  int expected = kNumFiles;
+  ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+}
+
+TEST_P(DBRateLimiterTest, VerifyFileChecksums) {
+  if (use_direct_io_ && !IsDirectIOSupported()) {
+    return;
+  }
+  Init();
+
+  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+
+  ASSERT_OK(db_->VerifyFileChecksums(GetReadOptions()));
+  // The files are tiny so there should have just been one read per file.
+  int expected = kNumFiles;
+  ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+}
+
+#endif  // !defined(ROCKSDB_LITE)
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ROCKSDB_NAMESPACE::port::InstallStackTraceHandler();
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}

db/db_test2.cc

@@ -3937,68 +3937,74 @@ TEST_F(DBTest2, RateLimitedCompactionReads) {
   const int kBytesPerKey = 1024;
   const int kNumL0Files = 4;
 
-  for (auto use_direct_io : {false, true}) {
+  for (int compaction_readahead_size : {0, 32 << 10}) {
-    if (use_direct_io && !IsDirectIOSupported()) {
+    for (auto use_direct_io : {false, true}) {
-      continue;
+      if (use_direct_io && !IsDirectIOSupported()) {
-    }
+        continue;
-    Options options = CurrentOptions();
-    options.compression = kNoCompression;
-    options.level0_file_num_compaction_trigger = kNumL0Files;
-    options.memtable_factory.reset(
-        test::NewSpecialSkipListFactory(kNumKeysPerFile));
-    // takes roughly one second, split into 100 x 10ms intervals. Each interval
-    // permits 5.12KB, which is smaller than the block size, so this test
-    // exercises the code for chunking reads.
-    options.rate_limiter.reset(NewGenericRateLimiter(
-        static_cast<int64_t>(kNumL0Files * kNumKeysPerFile *
-                             kBytesPerKey) /* rate_bytes_per_sec */,
-        10 * 1000 /* refill_period_us */, 10 /* fairness */,
-        RateLimiter::Mode::kReadsOnly));
-    options.use_direct_reads = options.use_direct_io_for_flush_and_compaction =
-        use_direct_io;
-    BlockBasedTableOptions bbto;
-    bbto.block_size = 16384;
-    bbto.no_block_cache = true;
-    options.table_factory.reset(NewBlockBasedTableFactory(bbto));
-    DestroyAndReopen(options);
-
-    for (int i = 0; i < kNumL0Files; ++i) {
-      for (int j = 0; j <= kNumKeysPerFile; ++j) {
-        ASSERT_OK(Put(Key(j), DummyString(kBytesPerKey)));
       }
-      ASSERT_OK(dbfull()->TEST_WaitForFlushMemTable());
+      Options options = CurrentOptions();
-      if (i + 1 < kNumL0Files) {
+      options.compaction_readahead_size = compaction_readahead_size;
-        ASSERT_EQ(i + 1, NumTableFilesAtLevel(0));
+      options.compression = kNoCompression;
+      options.level0_file_num_compaction_trigger = kNumL0Files;
+      options.memtable_factory.reset(
+          test::NewSpecialSkipListFactory(kNumKeysPerFile));
+      // takes roughly one second, split into 100 x 10ms intervals. Each
+      // interval permits 5.12KB, which is smaller than the block size, so this
+      // test exercises the code for chunking reads.
+      options.rate_limiter.reset(NewGenericRateLimiter(
+          static_cast<int64_t>(kNumL0Files * kNumKeysPerFile *
+                               kBytesPerKey) /* rate_bytes_per_sec */,
+          10 * 1000 /* refill_period_us */, 10 /* fairness */,
+          RateLimiter::Mode::kReadsOnly));
+      options.use_direct_reads =
+          options.use_direct_io_for_flush_and_compaction = use_direct_io;
+      BlockBasedTableOptions bbto;
+      bbto.block_size = 16384;
+      bbto.no_block_cache = true;
+      options.table_factory.reset(NewBlockBasedTableFactory(bbto));
+      DestroyAndReopen(options);
+
+      for (int i = 0; i < kNumL0Files; ++i) {
+        for (int j = 0; j <= kNumKeysPerFile; ++j) {
+          ASSERT_OK(Put(Key(j), DummyString(kBytesPerKey)));
+        }
+        ASSERT_OK(dbfull()->TEST_WaitForFlushMemTable());
+        if (i + 1 < kNumL0Files) {
+          ASSERT_EQ(i + 1, NumTableFilesAtLevel(0));
+        }
       }
-    }
+      ASSERT_OK(dbfull()->TEST_WaitForCompact());
-    ASSERT_OK(dbfull()->TEST_WaitForCompact());
+      ASSERT_EQ(0, NumTableFilesAtLevel(0));
-    ASSERT_EQ(0, NumTableFilesAtLevel(0));
 
-    ASSERT_EQ(0, options.rate_limiter->GetTotalBytesThrough(Env::IO_HIGH));
+      // should be slightly above 512KB due to non-data blocks read. Arbitrarily
-    // should be slightly above 512KB due to non-data blocks read. Arbitrarily
+      // chose 1MB as the upper bound on the total bytes read.
-    // chose 1MB as the upper bound on the total bytes read.
+      size_t rate_limited_bytes =
-    size_t rate_limited_bytes =
+          options.rate_limiter->GetTotalBytesThrough(Env::IO_TOTAL);
-        options.rate_limiter->GetTotalBytesThrough(Env::IO_LOW);
+      // There must be no charges at non-`IO_LOW` priorities.
-    // Include the explicit prefetch of the footer in direct I/O case.
+      ASSERT_EQ(rate_limited_bytes,
-    size_t direct_io_extra = use_direct_io ? 512 * 1024 : 0;
+                static_cast<size_t>(
-    ASSERT_GE(
+                    options.rate_limiter->GetTotalBytesThrough(Env::IO_LOW)));
-        rate_limited_bytes,
+      // Include the explicit prefetch of the footer in direct I/O case.
-        static_cast<size_t>(kNumKeysPerFile * kBytesPerKey * kNumL0Files));
+      size_t direct_io_extra = use_direct_io ? 512 * 1024 : 0;
-    ASSERT_LT(
+      ASSERT_GE(
-        rate_limited_bytes,
+          rate_limited_bytes,
-        static_cast<size_t>(2 * kNumKeysPerFile * kBytesPerKey * kNumL0Files +
+          static_cast<size_t>(kNumKeysPerFile * kBytesPerKey * kNumL0Files));
-                            direct_io_extra));
+      ASSERT_LT(
+          rate_limited_bytes,
+          static_cast<size_t>(2 * kNumKeysPerFile * kBytesPerKey * kNumL0Files +
+                              direct_io_extra));
 
-    Iterator* iter = db_->NewIterator(ReadOptions());
+      Iterator* iter = db_->NewIterator(ReadOptions());
-    ASSERT_OK(iter->status());
+      ASSERT_OK(iter->status());
-    for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
+      for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
-      ASSERT_EQ(iter->value().ToString(), DummyString(kBytesPerKey));
+        ASSERT_EQ(iter->value().ToString(), DummyString(kBytesPerKey));
+      }
+      delete iter;
+      // bytes read for user iterator shouldn't count against the rate limit.
+      ASSERT_EQ(rate_limited_bytes,
+                static_cast<size_t>(
+                    options.rate_limiter->GetTotalBytesThrough(Env::IO_LOW)));
     }
-    delete iter;
-    // bytes read for user iterator shouldn't count against the rate limit.
-    ASSERT_EQ(rate_limited_bytes,
-              static_cast<size_t>(
-                  options.rate_limiter->GetTotalBytesThrough(Env::IO_LOW)));
   }
 }
 #endif  // ROCKSDB_LITE

db/external_sst_file_ingestion_job.cc

@@ -212,6 +212,8 @@ Status ExternalSstFileIngestionJob::Prepare(
         std::string generated_checksum;
         std::string generated_checksum_func_name;
         std::string requested_checksum_func_name;
+        // TODO: rate limit file reads for checksum calculation during file
+        // ingestion.
         IOStatus io_s = GenerateOneFileChecksum(
             fs_.get(), files_to_ingest_[i].internal_file_path,
             db_options_.file_checksum_gen_factory.get(),
@@ -219,7 +221,8 @@ Status ExternalSstFileIngestionJob::Prepare(
             &generated_checksum_func_name,
             ingestion_options_.verify_checksums_readahead_size,
             db_options_.allow_mmap_reads, io_tracer_,
-            db_options_.rate_limiter.get());
+            db_options_.rate_limiter.get(),
+            Env::IO_TOTAL /* rate_limiter_priority */);
         if (!io_s.ok()) {
           status = io_s;
           ROCKS_LOG_WARN(db_options_.info_log,
@@ -907,12 +910,14 @@ IOStatus ExternalSstFileIngestionJob::GenerateChecksumForIngestedFile(
   std::string file_checksum;
   std::string file_checksum_func_name;
   std::string requested_checksum_func_name;
+  // TODO: rate limit file reads for checksum calculation during file ingestion.
   IOStatus io_s = GenerateOneFileChecksum(
       fs_.get(), file_to_ingest->internal_file_path,
       db_options_.file_checksum_gen_factory.get(), requested_checksum_func_name,
       &file_checksum, &file_checksum_func_name,
       ingestion_options_.verify_checksums_readahead_size,
-      db_options_.allow_mmap_reads, io_tracer_, db_options_.rate_limiter.get());
+      db_options_.allow_mmap_reads, io_tracer_, db_options_.rate_limiter.get(),
+      Env::IO_TOTAL /* rate_limiter_priority */);
   if (!io_s.ok()) {
     return io_s;
   }

db_stress_tool/cf_consistency_stress.cc

@@ -286,6 +286,8 @@ class CfConsistencyStressTest : public StressTest {
   }
 
   void VerifyDb(ThreadState* thread) const override {
+    // This `ReadOptions` is for validation purposes. Ignore
+    // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
     ReadOptions options(FLAGS_verify_checksum, true);
     // We must set total_order_seek to true because we are doing a SeekToFirst
     // on a column family whose memtables may support (by default) prefix-based
@@ -472,6 +474,8 @@ class CfConsistencyStressTest : public StressTest {
       *checksum = ret;
       return iter->status();
     };
+    // This `ReadOptions` is for validation purposes. Ignore
+    // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
     ReadOptions ropts;
     ropts.total_order_seek = true;
     ropts.snapshot = snapshot_guard.get();

db_stress_tool/db_stress_common.h

@@ -175,6 +175,7 @@ DECLARE_double(max_bytes_for_level_multiplier);
 DECLARE_int32(range_deletion_width);
 DECLARE_uint64(rate_limiter_bytes_per_sec);
 DECLARE_bool(rate_limit_bg_reads);
+DECLARE_bool(rate_limit_user_ops);
 DECLARE_uint64(sst_file_manager_bytes_per_sec);
 DECLARE_uint64(sst_file_manager_bytes_per_truncate);
 DECLARE_bool(use_txn);

db_stress_tool/db_stress_gflags.cc

@@ -546,6 +546,10 @@ DEFINE_uint64(rate_limiter_bytes_per_sec, 0, "Set options.rate_limiter value.");
 DEFINE_bool(rate_limit_bg_reads, false,
             "Use options.rate_limiter on compaction reads");
 
+DEFINE_bool(rate_limit_user_ops, false,
+            "When true use Env::IO_USER priority level to charge internal rate "
+            "limiter for reads associated with user operations.");
+
 DEFINE_uint64(sst_file_manager_bytes_per_sec, 0,
               "Set `Options::sst_file_manager` to delete at this rate. By "
               "default the deletion rate is unbounded.");

db_stress_tool/db_stress_test_base.cc

@@ -349,6 +349,8 @@ bool StressTest::VerifySecondaries() {
       fprintf(stderr, "Secondary failed to catch up with primary\n");
       return false;
     }
+    // This `ReadOptions` is for validation purposes. Ignore
+    // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
     ReadOptions ropts;
     ropts.total_order_seek = true;
     // Verify only the default column family since the primary may have
@@ -397,6 +399,8 @@ Status StressTest::AssertSame(DB* db, ColumnFamilyHandle* cf,
   if (cf->GetName() != snap_state.cf_at_name) {
     return s;
   }
+  // This `ReadOptions` is for validation purposes. Ignore
+  // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
   ReadOptions ropt;
   ropt.snapshot = snap_state.snapshot;
   Slice ts;
@@ -633,6 +637,8 @@ Status StressTest::RollbackTxn(Transaction* txn) {
 
 void StressTest::OperateDb(ThreadState* thread) {
   ReadOptions read_opts(FLAGS_verify_checksum, true);
+  read_opts.rate_limiter_priority =
+      FLAGS_rate_limit_user_ops ? Env::IO_USER : Env::IO_TOTAL;
   WriteOptions write_opts;
   auto shared = thread->shared;
   char value[100];
@@ -1133,6 +1139,8 @@ Status StressTest::TestIterate(ThreadState* thread,
     // to bounds, prefix extractor or reseeking. Sometimes we are comparing
     // iterators with the same set-up, and it doesn't hurt to check them
     // to be equal.
+    // This `ReadOptions` is for validation purposes. Ignore
+    // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
     ReadOptions cmp_ro;
     cmp_ro.timestamp = readoptionscopy.timestamp;
     cmp_ro.snapshot = snapshot;
@@ -1573,6 +1581,8 @@ Status StressTest::TestBackupRestore(
     std::string key_str = Key(rand_keys[0]);
     Slice key = key_str;
     std::string restored_value;
+    // This `ReadOptions` is for validation purposes. Ignore
+    // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
     ReadOptions read_opts;
     std::string ts_str;
     Slice ts;
@@ -1943,6 +1953,8 @@ void StressTest::TestAcquireSnapshot(ThreadState* thread,
                                      const std::string& keystr, uint64_t i) {
   Slice key = keystr;
   ColumnFamilyHandle* column_family = column_families_[rand_column_family];
+  // This `ReadOptions` is for validation purposes. Ignore
+  // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
   ReadOptions ropt;
 #ifndef ROCKSDB_LITE
   auto db_impl = static_cast_with_check<DBImpl>(db_->GetRootDB());
@@ -2096,6 +2108,8 @@ uint32_t StressTest::GetRangeHash(ThreadState* thread, const Snapshot* snapshot,
                                   const Slice& end_key) {
   const std::string kCrcCalculatorSepearator = ";";
   uint32_t crc = 0;
+  // This `ReadOptions` is for validation purposes. Ignore
+  // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
   ReadOptions ro;
   ro.snapshot = snapshot;
   ro.total_order_seek = true;

db_stress_tool/multi_ops_txns_stress.cc

@@ -477,6 +477,8 @@ Status MultiOpsTxnsStressTest::PrimaryKeyUpdateTxn(ThreadState* thread,
   });
 
   ReadOptions ropts;
+  ropts.rate_limiter_priority =
+      FLAGS_rate_limit_user_ops ? Env::IO_USER : Env::IO_TOTAL;
   std::string value;
   s = txn->GetForUpdate(ropts, old_pk, &value);
   if (!s.ok()) {
@@ -596,6 +598,8 @@ Status MultiOpsTxnsStressTest::SecondaryKeyUpdateTxn(ThreadState* thread,
   }
   ropts.total_order_seek = true;
   ropts.iterate_upper_bound = &iter_ub;
+  ropts.rate_limiter_priority =
+      FLAGS_rate_limit_user_ops ? Env::IO_USER : Env::IO_TOTAL;
   it = txn->GetIterator(ropts);
 
   assert(it);
@@ -620,6 +624,8 @@ Status MultiOpsTxnsStressTest::SecondaryKeyUpdateTxn(ThreadState* thread,
     std::string pk = Record::EncodePrimaryKey(record.a_value());
     std::string value;
     ReadOptions read_opts;
+    read_opts.rate_limiter_priority =
+        FLAGS_rate_limit_user_ops ? Env::IO_USER : Env::IO_TOTAL;
     read_opts.snapshot = txn->GetSnapshot();
     s = txn->GetForUpdate(read_opts, pk, &value);
     if (s.IsBusy() || s.IsTimedOut() || s.IsTryAgain() ||
@@ -722,6 +728,8 @@ Status MultiOpsTxnsStressTest::UpdatePrimaryIndexValueTxn(ThreadState* thread,
     RollbackTxn(txn).PermitUncheckedError();
   });
   ReadOptions ropts;
+  ropts.rate_limiter_priority =
+      FLAGS_rate_limit_user_ops ? Env::IO_USER : Env::IO_TOTAL;
   std::string value;
   s = txn->GetForUpdate(ropts, pk_str, &value);
   if (!s.ok()) {
@@ -851,6 +859,8 @@ void MultiOpsTxnsStressTest::VerifyDb(ThreadState* thread) const {
     std::string iter_ub_str(buf, sizeof(buf));
     Slice iter_ub = iter_ub_str;
 
+    // This `ReadOptions` is for validation purposes. Ignore
+    // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
     ReadOptions ropts;
     ropts.snapshot = snapshot;
     ropts.total_order_seek = true;
@@ -870,6 +880,8 @@ void MultiOpsTxnsStressTest::VerifyDb(ThreadState* thread) const {
     std::reverse(buf, buf + sizeof(buf));
     const std::string start_key(buf, sizeof(buf));
 
+    // This `ReadOptions` is for validation purposes. Ignore
+    // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
     ReadOptions ropts;
     ropts.snapshot = snapshot;
     ropts.total_order_seek = true;

db_stress_tool/no_batched_ops_stress.cc

@@ -21,6 +21,8 @@ class NonBatchedOpsStressTest : public StressTest {
   virtual ~NonBatchedOpsStressTest() {}
 
   void VerifyDb(ThreadState* thread) const override {
+    // This `ReadOptions` is for validation purposes. Ignore
+    // `FLAGS_rate_limit_user_ops` to avoid slowing any validation.
     ReadOptions options(FLAGS_verify_checksum, true);
     std::string ts_str;
     Slice ts;

file/file_prefetch_buffer.cc

@@ -24,7 +24,7 @@ namespace ROCKSDB_NAMESPACE {
 Status FilePrefetchBuffer::Prefetch(const IOOptions& opts,
                                     RandomAccessFileReader* reader,
                                     uint64_t offset, size_t n,
-                                    bool for_compaction) {
+                                    Env::IOPriority rate_limiter_priority) {
   if (!enable_ || reader == nullptr) {
     return Status::OK();
   }
@@ -90,7 +90,8 @@ Status FilePrefetchBuffer::Prefetch(const IOOptions& opts,
   Slice result;
   size_t read_len = static_cast<size_t>(roundup_len - chunk_len);
   s = reader->Read(opts, rounddown_offset + chunk_len, read_len, &result,
-                   buffer_.BufferStart() + chunk_len, nullptr, for_compaction);
+                   buffer_.BufferStart() + chunk_len, nullptr,
+                   rate_limiter_priority);
   if (!s.ok()) {
     return s;
   }
@@ -111,7 +112,8 @@ bool FilePrefetchBuffer::TryReadFromCache(const IOOptions& opts,
                                           RandomAccessFileReader* reader,
                                           uint64_t offset, size_t n,
                                           Slice* result, Status* status,
-                                          bool for_compaction) {
+                                          Env::IOPriority rate_limiter_priority,
+                                          bool for_compaction /* = false */) {
   if (track_min_offset_ && offset < min_offset_read_) {
     min_offset_read_ = static_cast<size_t>(offset);
   }
@@ -132,7 +134,7 @@ bool FilePrefetchBuffer::TryReadFromCache(const IOOptions& opts,
       Status s;
       if (for_compaction) {
         s = Prefetch(opts, reader, offset, std::max(n, readahead_size_),
-                     for_compaction);
+                     rate_limiter_priority);
       } else {
         if (implicit_auto_readahead_) {
           // Prefetch only if this read is sequential otherwise reset
@@ -152,7 +154,8 @@ bool FilePrefetchBuffer::TryReadFromCache(const IOOptions& opts,
             return false;
           }
         }
-        s = Prefetch(opts, reader, offset, n + readahead_size_, for_compaction);
+        s = Prefetch(opts, reader, offset, n + readahead_size_,
+                     rate_limiter_priority);
       }
       if (!s.ok()) {
         if (status) {

file/file_prefetch_buffer.h

@@ -68,12 +68,14 @@ class FilePrefetchBuffer {
         num_file_reads_(kMinNumFileReadsToStartAutoReadahead + 1) {}
 
   // Load data into the buffer from a file.
-  // reader : the file reader.
+  // reader                : the file reader.
-  // offset : the file offset to start reading from.
+  // offset                : the file offset to start reading from.
-  // n      : the number of bytes to read.
+  // n                     : the number of bytes to read.
-  // for_compaction : if prefetch is done for compaction read.
+  // rate_limiter_priority : rate limiting priority, or `Env::IO_TOTAL` to
+  //                         bypass.
   Status Prefetch(const IOOptions& opts, RandomAccessFileReader* reader,
-                  uint64_t offset, size_t n, bool for_compaction = false);
+                  uint64_t offset, size_t n,
+                  Env::IOPriority rate_limiter_priority);
 
   // Tries returning the data for a file read from this buffer if that data is
   // in the buffer.
@@ -81,15 +83,18 @@ class FilePrefetchBuffer {
   // It also does the exponential readahead when readahead_size is set as part
   // of the constructor.
   //
-  // opts           : the IO options to use.
+  // opts                  : the IO options to use.
-  // reader         : the file reader.
+  // reader                : the file reader.
-  // offset         : the file offset.
+  // offset                : the file offset.
-  // n              : the number of bytes.
+  // n                     : the number of bytes.
-  // result         : output buffer to put the data into.
+  // result                : output buffer to put the data into.
-  // s              : output status.
+  // s                     : output status.
-  // for_compaction : true if cache read is done for compaction read.
+  // rate_limiter_priority : rate limiting priority, or `Env::IO_TOTAL` to
+  //                         bypass.
+  // for_compaction        : true if cache read is done for compaction read.
   bool TryReadFromCache(const IOOptions& opts, RandomAccessFileReader* reader,
                         uint64_t offset, size_t n, Slice* result, Status* s,
+                        Env::IOPriority rate_limiter_priority,
                         bool for_compaction = false);
 
   // The minimum `offset` ever passed to TryReadFromCache(). This will nly be

file/file_util.cc

@@ -123,7 +123,8 @@ IOStatus GenerateOneFileChecksum(
     const std::string& requested_checksum_func_name, std::string* file_checksum,
     std::string* file_checksum_func_name,
     size_t verify_checksums_readahead_size, bool allow_mmap_reads,
-    std::shared_ptr<IOTracer>& io_tracer, RateLimiter* rate_limiter) {
+    std::shared_ptr<IOTracer>& io_tracer, RateLimiter* rate_limiter,
+    Env::IOPriority rate_limiter_priority) {
   if (checksum_factory == nullptr) {
     return IOStatus::InvalidArgument("Checksum factory is invalid");
   }
@@ -195,7 +196,8 @@ IOStatus GenerateOneFileChecksum(
         static_cast<size_t>(std::min(uint64_t{readahead_size}, size));
     if (!prefetch_buffer.TryReadFromCache(
             opts, reader.get(), offset, bytes_to_read, &slice,
-            nullptr /* status */, false /* for_compaction */)) {
+            nullptr /* status */, rate_limiter_priority,
+            false /* for_compaction */)) {
       return IOStatus::Corruption("file read failed");
     }
     if (slice.size() == 0) {

file/file_util.h

@@ -51,20 +51,8 @@ extern IOStatus GenerateOneFileChecksum(
     const std::string& requested_checksum_func_name, std::string* file_checksum,
     std::string* file_checksum_func_name,
     size_t verify_checksums_readahead_size, bool allow_mmap_reads,
-    std::shared_ptr<IOTracer>& io_tracer, RateLimiter* rate_limiter = nullptr);
+    std::shared_ptr<IOTracer>& io_tracer, RateLimiter* rate_limiter,
-
+    Env::IOPriority rate_limiter_priority);
-inline IOStatus GenerateOneFileChecksum(
-    const std::shared_ptr<FileSystem>& fs, const std::string& file_path,
-    FileChecksumGenFactory* checksum_factory,
-    const std::string& requested_checksum_func_name, std::string* file_checksum,
-    std::string* file_checksum_func_name,
-    size_t verify_checksums_readahead_size, bool allow_mmap_reads,
-    std::shared_ptr<IOTracer>& io_tracer) {
-  return GenerateOneFileChecksum(
-      fs.get(), file_path, checksum_factory, requested_checksum_func_name,
-      file_checksum, file_checksum_func_name, verify_checksums_readahead_size,
-      allow_mmap_reads, io_tracer);
-}
 
 inline IOStatus PrepareIOFromReadOptions(const ReadOptions& ro,
                                          SystemClock* clock, IOOptions& opts) {

file/random_access_file_reader.cc

@@ -116,10 +116,10 @@ IOStatus RandomAccessFileReader::Create(
   return io_s;
 }
 
-IOStatus RandomAccessFileReader::Read(const IOOptions& opts, uint64_t offset,
+IOStatus RandomAccessFileReader::Read(
-                                      size_t n, Slice* result, char* scratch,
+    const IOOptions& opts, uint64_t offset, size_t n, Slice* result,
-                                      AlignedBuf* aligned_buf,
+    char* scratch, AlignedBuf* aligned_buf,
-                                      bool for_compaction) const {
+    Env::IOPriority rate_limiter_priority) const {
   (void)aligned_buf;
 
   TEST_SYNC_POINT_CALLBACK("RandomAccessFileReader::Read", nullptr);
@@ -153,10 +153,11 @@ IOStatus RandomAccessFileReader::Read(const IOOptions& opts, uint64_t offset,
       buf.AllocateNewBuffer(read_size);
       while (buf.CurrentSize() < read_size) {
         size_t allowed;
-        if (for_compaction && rate_limiter_ != nullptr) {
+        if (rate_limiter_priority != Env::IO_TOTAL &&
+            rate_limiter_ != nullptr) {
           allowed = rate_limiter_->RequestToken(
               buf.Capacity() - buf.CurrentSize(), buf.Alignment(),
-              Env::IOPriority::IO_LOW, stats_, RateLimiter::OpType::kRead);
+              rate_limiter_priority, stats_, RateLimiter::OpType::kRead);
         } else {
           assert(buf.CurrentSize() == 0);
           allowed = read_size;
@@ -212,12 +213,13 @@ IOStatus RandomAccessFileReader::Read(const IOOptions& opts, uint64_t offset,
       const char* res_scratch = nullptr;
       while (pos < n) {
         size_t allowed;
-        if (for_compaction && rate_limiter_ != nullptr) {
+        if (rate_limiter_priority != Env::IO_TOTAL &&
+            rate_limiter_ != nullptr) {
           if (rate_limiter_->IsRateLimited(RateLimiter::OpType::kRead)) {
             sw.DelayStart();
           }
           allowed = rate_limiter_->RequestToken(n - pos, 0 /* alignment */,
-                                                Env::IOPriority::IO_LOW, stats_,
+                                                rate_limiter_priority, stats_,
                                                 RateLimiter::OpType::kRead);
           if (rate_limiter_->IsRateLimited(RateLimiter::OpType::kRead)) {
             sw.DelayStop();
@@ -311,10 +313,12 @@ bool TryMerge(FSReadRequest* dest, const FSReadRequest& src) {
   return true;
 }
 
-IOStatus RandomAccessFileReader::MultiRead(const IOOptions& opts,
+IOStatus RandomAccessFileReader::MultiRead(
-                                           FSReadRequest* read_reqs,
+    const IOOptions& opts, FSReadRequest* read_reqs, size_t num_reqs,
-                                           size_t num_reqs,
+    AlignedBuf* aligned_buf, Env::IOPriority rate_limiter_priority) const {
-                                           AlignedBuf* aligned_buf) const {
+  if (rate_limiter_priority != Env::IO_TOTAL) {
+    return IOStatus::NotSupported("Unable to rate limit MultiRead()");
+  }
   (void)aligned_buf;  // suppress warning of unused variable in LITE mode
   assert(num_reqs > 0);
 

file/random_access_file_reader.h

@@ -139,17 +139,26 @@ class RandomAccessFileReader {
   // 2. Otherwise, scratch is not used and can be null, the aligned_buf owns
   // the internally allocated buffer on return, and the result refers to a
   // region in aligned_buf.
+  //
+  // `rate_limiter_priority` is used to charge the internal rate limiter when
+  // enabled. The special value `Env::IO_TOTAL` makes this operation bypass the
+  // rate limiter.
   IOStatus Read(const IOOptions& opts, uint64_t offset, size_t n, Slice* result,
                 char* scratch, AlignedBuf* aligned_buf,
-                bool for_compaction = false) const;
+                Env::IOPriority rate_limiter_priority) const;
 
   // REQUIRES:
   // num_reqs > 0, reqs do not overlap, and offsets in reqs are increasing.
   // In non-direct IO mode, aligned_buf should be null;
   // In direct IO mode, aligned_buf stores the aligned buffer allocated inside
   // MultiRead, the result Slices in reqs refer to aligned_buf.
+  //
+  // `rate_limiter_priority` will be used to charge the internal rate limiter.
+  // It is not yet supported so the client must provide the special value
+  // `Env::IO_TOTAL` to bypass the rate limiter.
   IOStatus MultiRead(const IOOptions& opts, FSReadRequest* reqs,
-                     size_t num_reqs, AlignedBuf* aligned_buf) const;
+                     size_t num_reqs, AlignedBuf* aligned_buf,
+                     Env::IOPriority rate_limiter_priority) const;
 
   IOStatus Prefetch(uint64_t offset, size_t n) const {
     return file_->Prefetch(offset, n, IOOptions(), nullptr);

file/random_access_file_reader_test.cc

@@ -85,9 +85,9 @@ TEST_F(RandomAccessFileReaderTest, ReadDirectIO) {
   size_t len = page_size / 3;
   Slice result;
   AlignedBuf buf;
-  for (bool for_compaction : {true, false}) {
+  for (Env::IOPriority rate_limiter_priority : {Env::IO_LOW, Env::IO_TOTAL}) {
     ASSERT_OK(r->Read(IOOptions(), offset, len, &result, nullptr, &buf,
-                      for_compaction));
+                      rate_limiter_priority));
     ASSERT_EQ(result.ToString(), content.substr(offset, len));
   }
 }
@@ -138,8 +138,8 @@ TEST_F(RandomAccessFileReaderTest, MultiReadDirectIO) {
     reqs.push_back(std::move(r0));
     reqs.push_back(std::move(r1));
     AlignedBuf aligned_buf;
-    ASSERT_OK(
+    ASSERT_OK(r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf,
-        r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf));
+                           Env::IO_TOTAL /* rate_limiter_priority */));
 
     AssertResult(content, reqs);
 
@@ -183,8 +183,8 @@ TEST_F(RandomAccessFileReaderTest, MultiReadDirectIO) {
     reqs.push_back(std::move(r1));
     reqs.push_back(std::move(r2));
     AlignedBuf aligned_buf;
-    ASSERT_OK(
+    ASSERT_OK(r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf,
-        r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf));
+                           Env::IO_TOTAL /* rate_limiter_priority */));
 
     AssertResult(content, reqs);
 
@@ -228,8 +228,8 @@ TEST_F(RandomAccessFileReaderTest, MultiReadDirectIO) {
     reqs.push_back(std::move(r1));
     reqs.push_back(std::move(r2));
     AlignedBuf aligned_buf;
-    ASSERT_OK(
+    ASSERT_OK(r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf,
-        r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf));
+                           Env::IO_TOTAL /* rate_limiter_priority */));
 
     AssertResult(content, reqs);
 
@@ -265,8 +265,8 @@ TEST_F(RandomAccessFileReaderTest, MultiReadDirectIO) {
     reqs.push_back(std::move(r0));
     reqs.push_back(std::move(r1));
     AlignedBuf aligned_buf;
-    ASSERT_OK(
+    ASSERT_OK(r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf,
-        r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf));
+                           Env::IO_TOTAL /* rate_limiter_priority */));
 
     AssertResult(content, reqs);
 

include/rocksdb/options.h

@@ -491,9 +491,18 @@ struct DBOptions {
   // Default: Env::Default()
   Env* env = Env::Default();
 
-  // Use to control write/read rate of flush and compaction. Flush has higher
+  // Limits internal file read/write bandwidth:
-  // priority than compaction. Rate limiting is disabled if nullptr.
+  //
-  // If rate limiter is enabled, bytes_per_sync is set to 1MB by default.
+  // - Flush requests write bandwidth at `Env::IOPriority::IO_HIGH`
+  // - Compaction requests read and write bandwidth at
+  //   `Env::IOPriority::IO_LOW`
+  // - Reads associated with a `ReadOptions` can be charged at
+  //   `ReadOptions::rate_limiter_priority` (see that option's API doc for usage
+  //   and limitations).
+  //
+  // Rate limiting is disabled if nullptr. If rate limiter is enabled,
+  // bytes_per_sync is set to 1MB by default.
+  //
   // Default: nullptr
   std::shared_ptr<RateLimiter> rate_limiter = nullptr;
 
@@ -1560,6 +1569,26 @@ struct ReadOptions {
   // Default: false
   bool adaptive_readahead;
 
+  // For file reads associated with this option, charge the internal rate
+  // limiter (see `DBOptions::rate_limiter`) at the specified priority. The
+  // special value `Env::IO_TOTAL` disables charging the rate limiter.
+  //
+  // The rate limiting is bypassed no matter this option's value for file reads
+  // on plain tables (these can exist when `ColumnFamilyOptions::table_factory`
+  // is a `PlainTableFactory`) and cuckoo tables (these can exist when
+  // `ColumnFamilyOptions::table_factory` is a `CuckooTableFactory`).
+  //
+  // The new `DB::MultiGet()` APIs (i.e., the ones returning `void`) will return
+  // `Status::NotSupported` when that operation requires file read(s) and
+  // `rate_limiter_priority != Env::IO_TOTAL`.
+  //
+  // The bytes charged to rate limiter may not exactly match the file read bytes
+  // since there are some seemingly insignificant reads, like for file
+  // headers/footers, that we currently do not charge to rate limiter.
+  //
+  // Default: `Env::IO_TOTAL`.
+  Env::IOPriority rate_limiter_priority = Env::IO_TOTAL;
+
   ReadOptions();
   ReadOptions(bool cksum, bool cache);
 };

src.mk

@@ -445,6 +445,7 @@ TEST_MAIN_SOURCES =                                                     \
   db/db_options_test.cc                                                 \
   db/db_properties_test.cc                                              \
   db/db_range_del_test.cc                                               \
+  db/db_rate_limiter_test.cc                                            \
   db/db_secondary_test.cc                                               \
   db/db_sst_test.cc                                                     \
   db/db_statistics_test.cc                                              \

table/block_based/block_based_table_reader.cc

@@ -771,7 +771,9 @@ Status BlockBasedTable::PrefetchTail(
   IOOptions opts;
   Status s = file->PrepareIOOptions(ro, opts);
   if (s.ok()) {
-    s = (*prefetch_buffer)->Prefetch(opts, file, prefetch_off, prefetch_len);
+    s = (*prefetch_buffer)
+            ->Prefetch(opts, file, prefetch_off, prefetch_len,
+                       ro.rate_limiter_priority);
   }
   return s;
 }
@@ -1730,8 +1732,8 @@ void BlockBasedTable::RetrieveMultipleBlocks(
     IOOptions opts;
     IOStatus s = file->PrepareIOOptions(options, opts);
     if (s.ok()) {
-      s = file->MultiRead(opts, &read_reqs[0], read_reqs.size(),
+      s = file->MultiRead(opts, &read_reqs[0], read_reqs.size(), &direct_io_buf,
-                          &direct_io_buf);
+                          options.rate_limiter_priority);
     }
     if (!s.ok()) {
       // Discard all the results in this batch if there is any time out
@@ -2981,7 +2983,7 @@ Status BlockBasedTable::VerifyChecksumInBlocks(
     BlockHandle handle = index_iter->value().handle;
     BlockContents contents;
     BlockFetcher block_fetcher(
-        rep_->file.get(), &prefetch_buffer, rep_->footer, ReadOptions(), handle,
+        rep_->file.get(), &prefetch_buffer, rep_->footer, read_options, handle,
         &contents, rep_->ioptions, false /* decompress */,
         false /*maybe_compressed*/, BlockType::kData,
         UncompressionDict::GetEmptyDict(), rep_->persistent_cache_options);

table/block_based/partitioned_filter_block.cc

@@ -503,7 +503,8 @@ Status PartitionedFilterBlockReader::CacheDependencies(const ReadOptions& ro,
   s = rep->file->PrepareIOOptions(ro, opts);
   if (s.ok()) {
     s = prefetch_buffer->Prefetch(opts, rep->file.get(), prefetch_off,
-                                  static_cast<size_t>(prefetch_len));
+                                  static_cast<size_t>(prefetch_len),
+                                  ro.rate_limiter_priority);
   }
   if (!s.ok()) {
     return s;

table/block_based/partitioned_index_reader.cc

@@ -158,7 +158,8 @@ Status PartitionIndexReader::CacheDependencies(const ReadOptions& ro,
     Status s = rep->file->PrepareIOOptions(ro, opts);
     if (s.ok()) {
       s = prefetch_buffer->Prefetch(opts, rep->file.get(), prefetch_off,
-                                    static_cast<size_t>(prefetch_len));
+                                    static_cast<size_t>(prefetch_len),
+                                    ro.rate_limiter_priority);
     }
     if (!s.ok()) {
       return s;

table/block_fetcher.cc

@@ -70,9 +70,9 @@ inline bool BlockFetcher::TryGetFromPrefetchBuffer() {
     IOOptions opts;
     IOStatus io_s = file_->PrepareIOOptions(read_options_, opts);
     if (io_s.ok() &&
-        prefetch_buffer_->TryReadFromCache(opts, file_, handle_.offset(),
+        prefetch_buffer_->TryReadFromCache(
-                                           block_size_with_trailer_, &slice_,
+            opts, file_, handle_.offset(), block_size_with_trailer_, &slice_,
-                                           &io_s, for_compaction_)) {
+            &io_s, read_options_.rate_limiter_priority, for_compaction_)) {
       ProcessTrailerIfPresent();
       if (!io_status_.ok()) {
         return true;
@@ -245,17 +245,17 @@ IOStatus BlockFetcher::ReadBlockContents() {
     if (io_status_.ok()) {
       if (file_->use_direct_io()) {
         PERF_TIMER_GUARD(block_read_time);
-        io_status_ =
+        io_status_ = file_->Read(
-            file_->Read(opts, handle_.offset(), block_size_with_trailer_,
+            opts, handle_.offset(), block_size_with_trailer_, &slice_, nullptr,
-                        &slice_, nullptr, &direct_io_buf_, for_compaction_);
+            &direct_io_buf_, read_options_.rate_limiter_priority);
         PERF_COUNTER_ADD(block_read_count, 1);
         used_buf_ = const_cast<char*>(slice_.data());
       } else {
         PrepareBufferForBlockFromFile();
         PERF_TIMER_GUARD(block_read_time);
-        io_status_ =
+        io_status_ = file_->Read(opts, handle_.offset(),
-            file_->Read(opts, handle_.offset(), block_size_with_trailer_,
+                                 block_size_with_trailer_, &slice_, used_buf_,
-                        &slice_, used_buf_, nullptr, for_compaction_);
+                                 nullptr, read_options_.rate_limiter_priority);
         PERF_COUNTER_ADD(block_read_count, 1);
 #ifndef NDEBUG
         if (slice_.data() == &stack_buf_[0]) {

table/cuckoo/cuckoo_table_builder_test.cc

@@ -114,7 +114,8 @@ class CuckooBuilderTest : public testing::Test {
     for (uint32_t i = 0; i + 1 < table_size + cuckoo_block_size; ++i) {
       Slice read_slice;
       ASSERT_OK(file_reader->Read(IOOptions(), i * bucket_size, bucket_size,
-                                  &read_slice, nullptr, nullptr));
+                                  &read_slice, nullptr, nullptr,
+                                  Env::IO_TOTAL /* rate_limiter_priority */));
       size_t key_idx =
           std::find(expected_locations.begin(), expected_locations.end(), i) -
           expected_locations.begin();

table/cuckoo/cuckoo_table_reader.cc

@@ -141,8 +141,10 @@ CuckooTableReader::CuckooTableReader(
   cuckoo_block_size_ = *reinterpret_cast<const uint32_t*>(
       cuckoo_block_size->second.data());
   cuckoo_block_bytes_minus_one_ = cuckoo_block_size_ * bucket_length_ - 1;
-  status_ = file_->Read(IOOptions(), 0, static_cast<size_t>(file_size),
+  // TODO: rate limit reads of whole cuckoo tables.
-                        &file_data_, nullptr, nullptr);
+  status_ =
+      file_->Read(IOOptions(), 0, static_cast<size_t>(file_size), &file_data_,
+                  nullptr, nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
 }
 
 Status CuckooTableReader::Get(const ReadOptions& /*readOptions*/,

table/format.cc

@@ -369,17 +369,20 @@ Status ReadFooterFromFile(const IOOptions& opts, RandomAccessFileReader* file,
   // the required data is not in the prefetch buffer. Once deadline is enabled
   // for iterator, TryReadFromCache might do a readahead. Revisit to see if we
   // need to pass a timeout at that point
+  // TODO: rate limit footer reads.
   if (prefetch_buffer == nullptr ||
-      !prefetch_buffer->TryReadFromCache(IOOptions(), file, read_offset,
+      !prefetch_buffer->TryReadFromCache(
-                                         Footer::kMaxEncodedLength,
+          IOOptions(), file, read_offset, Footer::kMaxEncodedLength,
-                                         &footer_input, nullptr)) {
+          &footer_input, nullptr, Env::IO_TOTAL /* rate_limiter_priority */)) {
     if (file->use_direct_io()) {
       s = file->Read(opts, read_offset, Footer::kMaxEncodedLength,
-                     &footer_input, nullptr, &internal_buf);
+                     &footer_input, nullptr, &internal_buf,
+                     Env::IO_TOTAL /* rate_limiter_priority */);
     } else {
       footer_buf.reserve(Footer::kMaxEncodedLength);
       s = file->Read(opts, read_offset, Footer::kMaxEncodedLength,
-                     &footer_input, &footer_buf[0], nullptr);
+                     &footer_input, &footer_buf[0], nullptr,
+                     Env::IO_TOTAL /* rate_limiter_priority */);
     }
     if (!s.ok()) return s;
   }

table/mock_table.cc

@@ -291,7 +291,8 @@ Status MockTableFactory::GetIDFromFile(RandomAccessFileReader* file,
                                        uint32_t* id) const {
   char buf[4];
   Slice result;
-  Status s = file->Read(IOOptions(), 0, 4, &result, buf, nullptr);
+  Status s = file->Read(IOOptions(), 0, 4, &result, buf, nullptr,
+                        Env::IO_TOTAL /* rate_limiter_priority */);
   assert(result.size() == 4);
   *id = DecodeFixed32(buf);
   return s;

table/plain/plain_table_key_coding.cc

@@ -212,9 +212,11 @@ bool PlainTableFileReader::ReadNonMmap(uint32_t file_offset, uint32_t len,
     new_buffer->buf_len = 0;
   }
   Slice read_result;
+  // TODO: rate limit plain table reads.
   Status s =
       file_info_->file->Read(IOOptions(), file_offset, size_to_read,
-                             &read_result, new_buffer->buf.get(), nullptr);
+                             &read_result, new_buffer->buf.get(), nullptr,
+                             Env::IO_TOTAL /* rate_limiter_priority */);
   if (!s.ok()) {
     status_ = s;
     return false;

table/plain/plain_table_reader.cc

@@ -288,9 +288,9 @@ void PlainTableReader::FillBloom(const std::vector<uint32_t>& prefix_hashes) {
 Status PlainTableReader::MmapDataIfNeeded() {
   if (file_info_.is_mmap_mode) {
     // Get mmapped memory.
-    return file_info_.file->Read(IOOptions(), 0,
+    return file_info_.file->Read(
-                                 static_cast<size_t>(file_size_),
+        IOOptions(), 0, static_cast<size_t>(file_size_), &file_info_.file_data,
-                                 &file_info_.file_data, nullptr, nullptr);
+        nullptr, nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
   }
   return Status::OK();
 }

table/sst_file_dumper.cc

@@ -107,7 +107,8 @@ Status SstFileDumper::GetTableReader(const std::string& file_path) {
     uint64_t prefetch_off = file_size - prefetch_size;
     IOOptions opts;
     s = prefetch_buffer.Prefetch(opts, file_.get(), prefetch_off,
-                                 static_cast<size_t>(prefetch_size));
+                                 static_cast<size_t>(prefetch_size),
+                                 Env::IO_TOTAL /* rate_limiter_priority */);
 
     s = ReadFooterFromFile(opts, file_.get(), &prefetch_buffer, file_size,
                            &footer);

table/table_test.cc

@@ -1319,7 +1319,7 @@ class FileChecksumTestHelper {
     uint64_t offset = 0;
     Status s;
     s = file_reader_->Read(IOOptions(), offset, 2048, &result, scratch.get(),
-                           nullptr, false);
+                           nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
     if (!s.ok()) {
       return s;
     }
@@ -1327,7 +1327,8 @@ class FileChecksumTestHelper {
       file_checksum_generator->Update(scratch.get(), result.size());
       offset += static_cast<uint64_t>(result.size());
       s = file_reader_->Read(IOOptions(), offset, 2048, &result, scratch.get(),
-                             nullptr, false);
+                             nullptr,
+                             Env::IO_TOTAL /* rate_limiter_priority */);
       if (!s.ok()) {
         return s;
       }
@@ -5001,13 +5002,16 @@ TEST_F(BBTTailPrefetchTest, FilePrefetchBufferMinOffset) {
   IOOptions opts;
   buffer.TryReadFromCache(opts, nullptr /* reader */, 500 /* offset */,
                           10 /* n */, nullptr /* result */,
-                          nullptr /* status */);
+                          nullptr /* status */,
+                          Env::IO_TOTAL /* rate_limiter_priority */);
   buffer.TryReadFromCache(opts, nullptr /* reader */, 480 /* offset */,
                           10 /* n */, nullptr /* result */,
-                          nullptr /* status */);
+                          nullptr /* status */,
+                          Env::IO_TOTAL /* rate_limiter_priority */);
   buffer.TryReadFromCache(opts, nullptr /* reader */, 490 /* offset */,
                           10 /* n */, nullptr /* result */,
-                          nullptr /* status */);
+                          nullptr /* status */,
+                          Env::IO_TOTAL /* rate_limiter_priority */);
   ASSERT_EQ(480, buffer.min_offset_read());
 }
 

tools/db_bench_tool.cc

@@ -77,6 +77,7 @@
 #include "util/cast_util.h"
 #include "util/compression.h"
 #include "util/crc32c.h"
+#include "util/file_checksum_helper.h"
 #include "util/gflags_compat.h"
 #include "util/mutexlock.h"
 #include "util/random.h"
@@ -1077,6 +1078,14 @@ DEFINE_bool(adaptive_readahead, false,
             "carry forward internal auto readahead size from one file to next "
             "file at each level during iteration");
 
+DEFINE_bool(rate_limit_user_ops, false,
+            "When true use Env::IO_USER priority level to charge internal rate "
+            "limiter for reads associated with user operations.");
+
+DEFINE_bool(file_checksum, false,
+            "When true use FileChecksumGenCrc32cFactory for "
+            "file_checksum_gen_factory.");
+
 static enum ROCKSDB_NAMESPACE::CompressionType StringToCompressionType(
     const char* ctype) {
   assert(ctype);
@@ -3047,6 +3056,8 @@ class Benchmark {
       read_options_ = ReadOptions(FLAGS_verify_checksum, true);
       read_options_.total_order_seek = FLAGS_total_order_seek;
       read_options_.prefix_same_as_start = FLAGS_prefix_same_as_start;
+      read_options_.rate_limiter_priority =
+          FLAGS_rate_limit_user_ops ? Env::IO_USER : Env::IO_TOTAL;
       read_options_.tailing = FLAGS_use_tailing_iterator;
       read_options_.readahead_size = FLAGS_readahead_size;
       read_options_.adaptive_readahead = FLAGS_adaptive_readahead;
@@ -3313,6 +3324,12 @@ class Benchmark {
 #endif  // ROCKSDB_LITE
       } else if (name == "getmergeoperands") {
         method = &Benchmark::GetMergeOperands;
+#ifndef ROCKSDB_LITE
+      } else if (name == "verifychecksum") {
+        method = &Benchmark::VerifyChecksum;
+      } else if (name == "verifyfilechecksums") {
+        method = &Benchmark::VerifyFileChecksums;
+#endif                             // ROCKSDB_LITE
       } else if (!name.empty()) {  // No error message for empty name
         fprintf(stderr, "unknown benchmark '%s'\n", name.c_str());
         ErrorExit();
@@ -4267,6 +4284,11 @@ class Benchmark {
 
     options.listeners.emplace_back(listener_);
 
+    if (FLAGS_file_checksum) {
+      options.file_checksum_gen_factory.reset(
+          new FileChecksumGenCrc32cFactory());
+    }
+
     if (FLAGS_num_multi_db <= 1) {
       OpenDb(options, FLAGS_db, &db_);
     } else {
@@ -7207,6 +7229,35 @@ class Benchmark {
   }
 
 #ifndef ROCKSDB_LITE
+  void VerifyChecksum(ThreadState* thread) {
+    DB* db = SelectDB(thread);
+    ReadOptions ro;
+    ro.adaptive_readahead = FLAGS_adaptive_readahead;
+    ro.rate_limiter_priority =
+        FLAGS_rate_limit_user_ops ? Env::IO_USER : Env::IO_TOTAL;
+    ro.readahead_size = FLAGS_readahead_size;
+    Status s = db->VerifyChecksum(ro);
+    if (!s.ok()) {
+      fprintf(stderr, "VerifyChecksum() failed: %s\n", s.ToString().c_str());
+      exit(1);
+    }
+  }
+
+  void VerifyFileChecksums(ThreadState* thread) {
+    DB* db = SelectDB(thread);
+    ReadOptions ro;
+    ro.adaptive_readahead = FLAGS_adaptive_readahead;
+    ro.rate_limiter_priority =
+        FLAGS_rate_limit_user_ops ? Env::IO_USER : Env::IO_TOTAL;
+    ro.readahead_size = FLAGS_readahead_size;
+    Status s = db->VerifyFileChecksums(ro);
+    if (!s.ok()) {
+      fprintf(stderr, "VerifyFileChecksums() failed: %s\n",
+              s.ToString().c_str());
+      exit(1);
+    }
+  }
+
   // This benchmark stress tests Transactions.  For a given --duration (or
   // total number of --writes, a Transaction will perform a read-modify-write
   // to increment the value of a key in each of N(--transaction-sets) sets of

utilities/blob_db/blob_db_impl.cc

@@ -1541,15 +1541,16 @@ Status BlobDBImpl::GetRawBlobFromFile(const Slice& key, uint64_t file_number,
 
   {
     StopWatch read_sw(clock_, statistics_, BLOB_DB_BLOB_FILE_READ_MICROS);
+    // TODO: rate limit old blob DB file reads.
     if (reader->use_direct_io()) {
       s = reader->Read(IOOptions(), record_offset,
                        static_cast<size_t>(record_size), &blob_record, nullptr,
-                       &aligned_buf);
+                       &aligned_buf, Env::IO_TOTAL /* rate_limiter_priority */);
     } else {
       buf.reserve(static_cast<size_t>(record_size));
       s = reader->Read(IOOptions(), record_offset,
                        static_cast<size_t>(record_size), &blob_record, &buf[0],
-                       nullptr);
+                       nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
     }
     RecordTick(statistics_, BLOB_DB_BLOB_FILE_BYTES_READ, blob_record.size());
   }

utilities/blob_db/blob_dump_tool.cc

@@ -103,8 +103,8 @@ Status BlobDumpTool::Read(uint64_t offset, size_t size, Slice* result) {
     }
     buffer_.reset(new char[buffer_size_]);
   }
-  Status s =
+  Status s = reader_->Read(IOOptions(), offset, size, result, buffer_.get(),
-      reader_->Read(IOOptions(), offset, size, result, buffer_.get(), nullptr);
+                           nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
   if (!s.ok()) {
     return s;
   }

utilities/blob_db/blob_file.cc

@@ -112,13 +112,16 @@ Status BlobFile::ReadFooter(BlobLogFooter* bf) {
   std::string buf;
   AlignedBuf aligned_buf;
   Status s;
+  // TODO: rate limit reading footers from blob files.
   if (ra_file_reader_->use_direct_io()) {
     s = ra_file_reader_->Read(IOOptions(), footer_offset, BlobLogFooter::kSize,
-                              &result, nullptr, &aligned_buf);
+                              &result, nullptr, &aligned_buf,
+                              Env::IO_TOTAL /* rate_limiter_priority */);
   } else {
     buf.reserve(BlobLogFooter::kSize + 10);
     s = ra_file_reader_->Read(IOOptions(), footer_offset, BlobLogFooter::kSize,
-                              &result, &buf[0], nullptr);
+                              &result, &buf[0], nullptr,
+                              Env::IO_TOTAL /* rate_limiter_priority */);
   }
   if (!s.ok()) return s;
   if (result.size() != BlobLogFooter::kSize) {
@@ -235,13 +238,16 @@ Status BlobFile::ReadMetadata(const std::shared_ptr<FileSystem>& fs,
   std::string header_buf;
   AlignedBuf aligned_buf;
   Slice header_slice;
+  // TODO: rate limit reading headers from blob files.
   if (file_reader->use_direct_io()) {
     s = file_reader->Read(IOOptions(), 0, BlobLogHeader::kSize, &header_slice,
-                          nullptr, &aligned_buf);
+                          nullptr, &aligned_buf,
+                          Env::IO_TOTAL /* rate_limiter_priority */);
   } else {
     header_buf.reserve(BlobLogHeader::kSize);
     s = file_reader->Read(IOOptions(), 0, BlobLogHeader::kSize, &header_slice,
-                          &header_buf[0], nullptr);
+                          &header_buf[0], nullptr,
+                          Env::IO_TOTAL /* rate_limiter_priority */);
   }
   if (!s.ok()) {
     ROCKS_LOG_ERROR(info_log_,
@@ -275,15 +281,17 @@ Status BlobFile::ReadMetadata(const std::shared_ptr<FileSystem>& fs,
   }
   std::string footer_buf;
   Slice footer_slice;
+  // TODO: rate limit reading footers from blob files.
   if (file_reader->use_direct_io()) {
     s = file_reader->Read(IOOptions(), file_size - BlobLogFooter::kSize,
                           BlobLogFooter::kSize, &footer_slice, nullptr,
-                          &aligned_buf);
+                          &aligned_buf,
+                          Env::IO_TOTAL /* rate_limiter_priority */);
   } else {
     footer_buf.reserve(BlobLogFooter::kSize);
     s = file_reader->Read(IOOptions(), file_size - BlobLogFooter::kSize,
                           BlobLogFooter::kSize, &footer_slice, &footer_buf[0],
-                          nullptr);
+                          nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
   }
   if (!s.ok()) {
     ROCKS_LOG_ERROR(info_log_,

utilities/cache_dump_load_impl.h

@@ -258,7 +258,8 @@ class FromFileCacheDumpReader : public CacheDumpReader {
 
     while (to_read > 0) {
       io_s = file_reader_->Read(IOOptions(), offset_, to_read, &result_,
-                                buffer_, nullptr);
+                                buffer_, nullptr,
+                                Env::IO_TOTAL /* rate_limiter_priority */);
       if (!io_s.ok()) {
         return io_s;
       }

utilities/persistent_cache/block_cache_tier_file.cc

@@ -238,7 +238,7 @@ bool RandomAccessCacheFile::Read(const LBA& lba, Slice* key, Slice* val,
 
   Slice result;
   Status s = freader_->Read(IOOptions(), lba.off_, lba.size_, &result, scratch,
-                            nullptr);
+                            nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
   if (!s.ok()) {
     Error(log_, "Error reading from file %s. %s", Path().c_str(),
           s.ToString().c_str());

utilities/trace/file_trace_reader_writer.cc

@@ -42,7 +42,8 @@ Status FileTraceReader::Reset() {
 Status FileTraceReader::Read(std::string* data) {
   assert(file_reader_ != nullptr);
   Status s = file_reader_->Read(IOOptions(), offset_, kTraceMetadataSize,
-                                &result_, buffer_, nullptr);
+                                &result_, buffer_, nullptr,
+                                Env::IO_TOTAL /* rate_limiter_priority */);
   if (!s.ok()) {
     return s;
   }
@@ -67,7 +68,7 @@ Status FileTraceReader::Read(std::string* data) {
       bytes_to_read > kBufferSize ? kBufferSize : bytes_to_read;
   while (to_read > 0) {
     s = file_reader_->Read(IOOptions(), offset_, to_read, &result_, buffer_,
-                           nullptr);
+                           nullptr, Env::IO_TOTAL /* rate_limiter_priority */);
     if (!s.ok()) {
       return s;
     }