Set Read rate limiter priority dynamically and pass it to FS (#9996)

Summary:
### Context:
Background compactions and flush generate large reads and writes, and can be long running, especially for universal compaction. In some cases, this can impact foreground reads and writes by users.

### Solution
User, Flush, and Compaction reads share some code path. For this task, we update the rate_limiter_priority in ReadOptions for code paths (e.g. FindTable (mainly in BlockBasedTable::Open()) and various iterators), and eventually update the rate_limiter_priority in IOOptions for FSRandomAccessFile.

**This PR is for the Read path.** The **Read:** dynamic priority for different state are listed as follows:

| State | Normal | Delayed | Stalled |
| ----- | ------ | ------- | ------- |
|  Flush (verification read in BuildTable()) | IO_USER | IO_USER | IO_USER |
|  Compaction | IO_LOW  | IO_USER | IO_USER |
|  User | User provided | User provided | User provided |

We will respect the read_options that the user provided and will not set it.
The only sst read for Flush is the verification read in BuildTable(). It claims to be "regard as user read".

**Details**
1. Set read_options.rate_limiter_priority dynamically:
- User: Do not update the read_options. Use the read_options that the user provided.
- Compaction: Update read_options in CompactionJob::ProcessKeyValueCompaction().
- Flush: Update read_options in BuildTable().

2. Pass the rate limiter priority to FSRandomAccessFile functions:
- After calling the FindTable(), read_options is passed through GetTableReader(table_cache.cc), BlockBasedTableFactory::NewTableReader(block_based_table_factory.cc), and BlockBasedTable::Open(). The Open() needs some updates for the ReadOptions variable and the updates are also needed for the called functions,  including PrefetchTail(), PrepareIOOptions(), ReadFooterFromFile(), ReadMetaIndexblock(), ReadPropertiesBlock(), PrefetchIndexAndFilterBlocks(), and ReadRangeDelBlock().
- In RandomAccessFileReader, the functions to be updated include Read(), MultiRead(), ReadAsync(), and Prefetch().
- Update the downstream functions of NewIndexIterator(), NewDataBlockIterator(), and BlockBasedTableIterator().

### Test Plans
Add unit tests.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9996

Reviewed By: anand1976

Differential Revision: D36452483

Pulled By: gitbw95

fbshipit-source-id: 60978204a4f849bb9261cb78d9bc1cb56d6008cf

HISTORY.md

@@ -30,7 +30,8 @@
 ### Behavior changes
 * Enforce the existing contract of SingleDelete so that SingleDelete cannot be mixed with Delete because it leads to undefined behavior. Fix a number of unit tests that violate the contract but happen to pass.
 * ldb `--try_load_options` default to true if `--db` is specified and not creating a new DB, the user can still explicitly disable that by `--try_load_options=false` (or explicitly enable that by `--try_load_options`).
-* During Flush write or Compaction write, the WriteController is used to determine whether DB writes are stalled or slowed down. The priority (Env::IOPriority) can then be determined accordingly and be passed in IOOptions to the file system.
+* During Flush write or Compaction write/read, the WriteController is used to determine whether DB writes are stalled or slowed down. The priority (Env::IOPriority) can then be determined accordingly and be passed in IOOptions to the file system.
+
 
 ## 7.2.0 (04/15/2022)
 ### Bug Fixes

db/builder.cc

@@ -336,6 +336,7 @@ Status BuildTable(
       // we will regrad this verification as user reads since the goal is
       // to cache it here for further user reads
       ReadOptions read_options;
+      read_options.rate_limiter_priority = Env::IO_USER;
       std::unique_ptr<InternalIterator> it(table_cache->NewIterator(
           read_options, file_options, tboptions.internal_comparator, *meta,
           nullptr /* range_del_agg */, mutable_cf_options.prefix_extractor,

db/compaction/compaction_job.cc

@@ -1350,7 +1350,7 @@ 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;
+  read_options.rate_limiter_priority = GetRateLimiterPriority();
   // Compaction iterators shouldn't be confined to a single prefix.
   // Compactions use Seek() for
   // (a) concurrent compactions,

db/db_rate_limiter_test.cc

@@ -116,9 +116,8 @@ TEST_P(DBRateLimiterOnReadTest, Get) {
   }
   Init();
 
-  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
-
-  int expected = 0;
+  // In Init(), compaction may request tokens for `Env::IO_USER`.
+  int64_t expected = options_.rate_limiter->GetTotalRequests(Env::IO_USER);
   for (int i = 0; i < kNumFiles; ++i) {
     {
       std::string value;
@@ -146,7 +145,8 @@ TEST_P(DBRateLimiterOnReadTest, NewMultiGet) {
   }
   Init();
 
-  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+  // In Init(), compaction may request tokens for `Env::IO_USER`.
+  int64_t expected = options_.rate_limiter->GetTotalRequests(Env::IO_USER);
 
   const int kNumKeys = kNumFiles * kNumKeysPerFile;
   {
@@ -166,7 +166,7 @@ TEST_P(DBRateLimiterOnReadTest, NewMultiGet) {
       ASSERT_TRUE(statuses[i].IsNotSupported());
     }
   }
-  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+  ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
 }
 
 TEST_P(DBRateLimiterOnReadTest, OldMultiGet) {
@@ -177,10 +177,10 @@ TEST_P(DBRateLimiterOnReadTest, OldMultiGet) {
   }
   Init();
 
-  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+  // In Init(), compaction may request tokens for `Env::IO_USER`.
+  int64_t expected = 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);
@@ -207,10 +207,10 @@ TEST_P(DBRateLimiterOnReadTest, Iterator) {
   }
   Init();
 
+  // In Init(), compaction may request tokens for `Env::IO_USER`.
+  int64_t expected = options_.rate_limiter->GetTotalRequests(Env::IO_USER);
   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));
@@ -236,12 +236,12 @@ TEST_P(DBRateLimiterOnReadTest, VerifyChecksum) {
     return;
   }
   Init();
-
-  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+  // In Init(), compaction may request tokens for `Env::IO_USER`.
+  int64_t expected = 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;
+  expected += kNumFiles;
   ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
 }
 
@@ -251,11 +251,12 @@ TEST_P(DBRateLimiterOnReadTest, VerifyFileChecksums) {
   }
   Init();
 
-  ASSERT_EQ(0, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
+  // In Init(), compaction may request tokens for `Env::IO_USER`.
+  int64_t expected = 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;
+  expected += kNumFiles;
   ASSERT_EQ(expected, options_.rate_limiter->GetTotalRequests(Env::IO_USER));
 }
 

db/db_test2.cc

@@ -3987,12 +3987,14 @@ TEST_F(DBTest2, RateLimitedCompactionReads) {
 
       // should be slightly above 512KB due to non-data blocks read. Arbitrarily
       // chose 1MB as the upper bound on the total bytes read.
-      size_t rate_limited_bytes =
-          options.rate_limiter->GetTotalBytesThrough(Env::IO_TOTAL);
-      // There must be no charges at non-`IO_LOW` priorities.
+      size_t rate_limited_bytes = static_cast<size_t>(
+          options.rate_limiter->GetTotalBytesThrough(Env::IO_TOTAL));
+      // The charges can exist for `IO_LOW` and `IO_USER` priorities.
+      size_t rate_limited_bytes_by_pri =
+          options.rate_limiter->GetTotalBytesThrough(Env::IO_LOW) +
+          options.rate_limiter->GetTotalBytesThrough(Env::IO_USER);
       ASSERT_EQ(rate_limited_bytes,
-                static_cast<size_t>(
-                    options.rate_limiter->GetTotalBytesThrough(Env::IO_LOW)));
+                static_cast<size_t>(rate_limited_bytes_by_pri));
       // Include the explicit prefetch of the footer in direct I/O case.
       size_t direct_io_extra = use_direct_io ? 512 * 1024 : 0;
       ASSERT_GE(
@@ -4010,9 +4012,11 @@ TEST_F(DBTest2, RateLimitedCompactionReads) {
       }
       delete iter;
       // bytes read for user iterator shouldn't count against the rate limit.
+      rate_limited_bytes_by_pri =
+          options.rate_limiter->GetTotalBytesThrough(Env::IO_LOW) +
+          options.rate_limiter->GetTotalBytesThrough(Env::IO_USER);
       ASSERT_EQ(rate_limited_bytes,
-                static_cast<size_t>(
-                    options.rate_limiter->GetTotalBytesThrough(Env::IO_LOW)));
+                static_cast<size_t>(rate_limited_bytes_by_pri));
     }
   }
 }

file/file_util.h

@@ -78,6 +78,8 @@ inline IOStatus PrepareIOFromReadOptions(const ReadOptions& ro,
       (!opts.timeout.count() || ro.io_timeout < opts.timeout)) {
     opts.timeout = ro.io_timeout;
   }
+
+  opts.rate_limiter_priority = ro.rate_limiter_priority;
   return IOStatus::OK();
 }
 

file/random_access_file_reader.h

@@ -172,8 +172,11 @@ class RandomAccessFileReader {
                      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);
+  IOStatus Prefetch(uint64_t offset, size_t n,
+                    const Env::IOPriority rate_limiter_priority) const {
+    IOOptions opts;
+    opts.rate_limiter_priority = rate_limiter_priority;
+    return file_->Prefetch(offset, n, opts, nullptr);
   }
 
   FSRandomAccessFile* file() { return file_.get(); }

table/block_based/binary_search_index_reader.cc

@@ -47,7 +47,8 @@ InternalIteratorBase<IndexValue>* BinarySearchIndexReader::NewIterator(
   const bool no_io = (read_options.read_tier == kBlockCacheTier);
   CachableEntry<Block> index_block;
   const Status s =
-      GetOrReadIndexBlock(no_io, get_context, lookup_context, &index_block);
+      GetOrReadIndexBlock(no_io, read_options.rate_limiter_priority,
+                          get_context, lookup_context, &index_block);
   if (!s.ok()) {
     if (iter != nullptr) {
       iter->Invalidate(s);

table/block_based/block_based_table_iterator.cc

@@ -234,7 +234,7 @@ void BlockBasedTableIterator::InitDataBlock() {
     //   Enabled from the very first IO when ReadOptions.readahead_size is set.
     block_prefetcher_.PrefetchIfNeeded(
         rep, data_block_handle, read_options_.readahead_size, is_for_compaction,
-        read_options_.async_io);
+        read_options_.async_io, read_options_.rate_limiter_priority);
     Status s;
     table_->NewDataBlockIterator<DataBlockIter>(
         read_options_, data_block_handle, &block_iter_, BlockType::kData,

table/block_based/block_based_table_reader.cc

@@ -561,7 +561,7 @@ Status BlockBasedTable::Open(
   Footer footer;
   std::unique_ptr<FilePrefetchBuffer> prefetch_buffer;
 
-  // Only retain read_options.deadline and read_options.io_timeout.
+  // From read_options, retain deadline, io_timeout, and rate_limiter_priority.
   // In future, we may retain more
   // options. Specifically, w ignore verify_checksums and default to
   // checksum verification anyway when creating the index and filter
@@ -569,6 +569,7 @@ Status BlockBasedTable::Open(
   ReadOptions ro;
   ro.deadline = read_options.deadline;
   ro.io_timeout = read_options.io_timeout;
+  ro.rate_limiter_priority = read_options.rate_limiter_priority;
 
   // prefetch both index and filters, down to all partitions
   const bool prefetch_all = prefetch_index_and_filter_in_cache || level == 0;
@@ -766,7 +767,8 @@ Status BlockBasedTable::PrefetchTail(
 
   // Try file system prefetch
   if (!file->use_direct_io() && !force_direct_prefetch) {
-    if (!file->Prefetch(prefetch_off, prefetch_len).IsNotSupported()) {
+    if (!file->Prefetch(prefetch_off, prefetch_len, ro.rate_limiter_priority)
+             .IsNotSupported()) {
       prefetch_buffer->reset(new FilePrefetchBuffer(
           0 /* readahead_size */, 0 /* max_readahead_size */,
           false /* enable */, true /* track_min_offset */));
@@ -778,6 +780,7 @@ Status BlockBasedTable::PrefetchTail(
   prefetch_buffer->reset(
       new FilePrefetchBuffer(0 /* readahead_size */, 0 /* max_readahead_size */,
                              true /* enable */, true /* track_min_offset */));
+
   IOOptions opts;
   Status s = file->PrepareIOOptions(ro, opts);
   if (s.ok()) {

table/block_based/block_prefetcher.cc

@@ -8,13 +8,14 @@
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
 #include "table/block_based/block_prefetcher.h"
 
+#include "rocksdb/file_system.h"
 #include "table/block_based/block_based_table_reader.h"
 
 namespace ROCKSDB_NAMESPACE {
-void BlockPrefetcher::PrefetchIfNeeded(const BlockBasedTable::Rep* rep,
-                                       const BlockHandle& handle,
-                                       size_t readahead_size,
-                                       bool is_for_compaction, bool async_io) {
+void BlockPrefetcher::PrefetchIfNeeded(
+    const BlockBasedTable::Rep* rep, const BlockHandle& handle,
+    const size_t readahead_size, bool is_for_compaction, const bool async_io,
+    const Env::IOPriority rate_limiter_priority) {
   if (is_for_compaction) {
     rep->CreateFilePrefetchBufferIfNotExists(
         compaction_readahead_size_, compaction_readahead_size_,
@@ -84,7 +85,8 @@ void BlockPrefetcher::PrefetchIfNeeded(const BlockBasedTable::Rep* rep,
   // we can fallback to reading from disk if Prefetch fails.
   Status s = rep->file->Prefetch(
       handle.offset(),
-      BlockBasedTable::BlockSizeWithTrailer(handle) + readahead_size_);
+      BlockBasedTable::BlockSizeWithTrailer(handle) + readahead_size_,
+      rate_limiter_priority);
   if (s.IsNotSupported()) {
     rep->CreateFilePrefetchBufferIfNotExists(initial_auto_readahead_size_,
                                              max_auto_readahead_size,

table/block_based/block_prefetcher.h

@@ -20,7 +20,8 @@ class BlockPrefetcher {
 
   void PrefetchIfNeeded(const BlockBasedTable::Rep* rep,
                         const BlockHandle& handle, size_t readahead_size,
-                        bool is_for_compaction, bool async_io);
+                        bool is_for_compaction, bool async_io,
+                        Env::IOPriority rate_limiter_priority);
   FilePrefetchBuffer* prefetch_buffer() { return prefetch_buffer_.get(); }
 
   void UpdateReadPattern(const uint64_t& offset, const size_t& len) {

table/block_based/hash_index_reader.cc

@@ -117,7 +117,8 @@ InternalIteratorBase<IndexValue>* HashIndexReader::NewIterator(
   const bool no_io = (read_options.read_tier == kBlockCacheTier);
   CachableEntry<Block> index_block;
   const Status s =
-      GetOrReadIndexBlock(no_io, get_context, lookup_context, &index_block);
+      GetOrReadIndexBlock(no_io, read_options.rate_limiter_priority,
+                          get_context, lookup_context, &index_block);
   if (!s.ok()) {
     if (iter != nullptr) {
       iter->Invalidate(s);

table/block_based/index_reader_common.cc

@@ -33,7 +33,7 @@ Status BlockBasedTable::IndexReaderCommon::ReadIndexBlock(
 }
 
 Status BlockBasedTable::IndexReaderCommon::GetOrReadIndexBlock(
-    bool no_io, GetContext* get_context,
+    bool no_io, Env::IOPriority rate_limiter_priority, GetContext* get_context,
     BlockCacheLookupContext* lookup_context,
     CachableEntry<Block>* index_block) const {
   assert(index_block != nullptr);
@@ -44,6 +44,7 @@ Status BlockBasedTable::IndexReaderCommon::GetOrReadIndexBlock(
   }
 
   ReadOptions read_options;
+  read_options.rate_limiter_priority = rate_limiter_priority;
   if (no_io) {
     read_options.read_tier = kBlockCacheTier;
   }

table/block_based/index_reader_common.h

@@ -66,7 +66,8 @@ class BlockBasedTable::IndexReaderCommon : public BlockBasedTable::IndexReader {
     return table_->get_rep()->table_options.cache_index_and_filter_blocks;
   }
 
-  Status GetOrReadIndexBlock(bool no_io, GetContext* get_context,
+  Status GetOrReadIndexBlock(bool no_io, Env::IOPriority rate_limiter_priority,
+                             GetContext* get_context,
                              BlockCacheLookupContext* lookup_context,
                              CachableEntry<Block>* index_block) const;
 

table/block_based/partitioned_index_iterator.cc

@@ -91,7 +91,8 @@ void PartitionedIndexIterator::InitPartitionedIndexBlock() {
     //   Enabled from the very first IO when ReadOptions.readahead_size is set.
     block_prefetcher_.PrefetchIfNeeded(
         rep, partitioned_index_handle, read_options_.readahead_size,
-        is_for_compaction, read_options_.async_io);
+        is_for_compaction, read_options_.async_io,
+        read_options_.rate_limiter_priority);
     Status s;
     table_->NewDataBlockIterator<IndexBlockIter>(
         read_options_, partitioned_index_handle, &block_iter_,

table/block_based/partitioned_index_reader.cc

@@ -49,7 +49,8 @@ InternalIteratorBase<IndexValue>* PartitionIndexReader::NewIterator(
   const bool no_io = (read_options.read_tier == kBlockCacheTier);
   CachableEntry<Block> index_block;
   const Status s =
-      GetOrReadIndexBlock(no_io, get_context, lookup_context, &index_block);
+      GetOrReadIndexBlock(no_io, read_options.rate_limiter_priority,
+                          get_context, lookup_context, &index_block);
   if (!s.ok()) {
     if (iter != nullptr) {
       iter->Invalidate(s);
@@ -82,6 +83,7 @@ InternalIteratorBase<IndexValue>* PartitionIndexReader::NewIterator(
     ro.io_timeout = read_options.io_timeout;
     ro.adaptive_readahead = read_options.adaptive_readahead;
     ro.async_io = read_options.async_io;
+    ro.rate_limiter_priority = read_options.rate_limiter_priority;
 
     // We don't return pinned data from index blocks, so no need
     // to set `block_contents_pinned`.
@@ -119,8 +121,9 @@ Status PartitionIndexReader::CacheDependencies(const ReadOptions& ro,
 
   CachableEntry<Block> index_block;
   {
-    Status s = GetOrReadIndexBlock(false /* no_io */, nullptr /* get_context */,
-                                   &lookup_context, &index_block);
+    Status s = GetOrReadIndexBlock(false /* no_io */, ro.rate_limiter_priority,
+                                   nullptr /* get_context */, &lookup_context,
+                                   &index_block);
     if (!s.ok()) {
       return s;
     }

table/format.cc

@@ -372,17 +372,17 @@ Status ReadFooterFromFile(const IOOptions& opts, RandomAccessFileReader* file,
   // TODO: rate limit footer reads.
   if (prefetch_buffer == nullptr ||
       !prefetch_buffer->TryReadFromCache(
-          IOOptions(), file, read_offset, Footer::kMaxEncodedLength,
-          &footer_input, nullptr, Env::IO_TOTAL /* rate_limiter_priority */)) {
+          opts, file, read_offset, Footer::kMaxEncodedLength, &footer_input,
+          nullptr, opts.rate_limiter_priority)) {
     if (file->use_direct_io()) {
       s = file->Read(opts, read_offset, Footer::kMaxEncodedLength,
                      &footer_input, nullptr, &internal_buf,
-                     Env::IO_TOTAL /* rate_limiter_priority */);
+                     opts.rate_limiter_priority);
     } else {
       footer_buf.reserve(Footer::kMaxEncodedLength);
       s = file->Read(opts, read_offset, Footer::kMaxEncodedLength,
                      &footer_input, &footer_buf[0], nullptr,
-                     Env::IO_TOTAL /* rate_limiter_priority */);
+                     opts.rate_limiter_priority);
     }
     if (!s.ok()) return s;
   }