Deprecate removeScanCountLimit in NewLRUCache

Summary: It is no longer used by the implementation, so we should also remove it from the public API.

Test Plan: make check

Reviewers: sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D34971

HISTORY.md

@@ -1,7 +1,7 @@
 # Rocksdb Change Log
 
 ### Unreleased Features
-* Changed the LRU caching algorithm so that referenced blocks (by iterators) are never evicted
+* Changed the LRU caching algorithm so that referenced blocks (by iterators) are never evicted. This change made parameter removeScanCountLimit obsolete. Because of that NewLRUCache doesn't take three arguments anymore. table_cache_remove_scan_limit option is also removed
 * By default we now optimize the compilation for the compilation platform (using -march=native). If you want to build portable binary, use 'PORTABLE=1' before the make command.
 * We now allow level-compaction to place files in different paths by
   specifying them in db_paths along with the target_size.

db/c.cc

@@ -1613,7 +1613,7 @@ void rocksdb_options_set_table_cache_numshardbits(
 
 void rocksdb_options_set_table_cache_remove_scan_count_limit(
     rocksdb_options_t* opt, int v) {
-  opt->rep.table_cache_remove_scan_count_limit = v;
+  // this option is deprecated
 }
 
 void rocksdb_options_set_arena_block_size(

db/compaction_job_test.cc

@@ -26,7 +26,7 @@ class CompactionJobTest : public testing::Test {
       : env_(Env::Default()),
         dbname_(test::TmpDir() + "/compaction_job_test"),
         mutable_cf_options_(Options(), ImmutableCFOptions(Options())),
-        table_cache_(NewLRUCache(50000, 16, 8)),
+        table_cache_(NewLRUCache(50000, 16)),
         write_buffer_(db_options_.db_write_buffer_size),
         versions_(new VersionSet(dbname_, &db_options_, env_options_,
                                  table_cache_.get(), &write_buffer_,

db/db_bench.cc

@@ -307,8 +307,6 @@ DEFINE_int32(cache_numshardbits, -1, "Number of shards for the block cache"
              " is 2 ** cache_numshardbits. Negative means use default settings."
              " This is applied only if FLAGS_cache_size is non-negative.");
 
-DEFINE_int32(cache_remove_scan_count_limit, 32, "");
-
 DEFINE_bool(verify_checksum, false, "Verify checksum for every block read"
             " from storage");
 
@@ -1357,8 +1355,7 @@ class Benchmark {
       : cache_(
             FLAGS_cache_size >= 0
                 ? (FLAGS_cache_numshardbits >= 1
-                       ? NewLRUCache(FLAGS_cache_size, FLAGS_cache_numshardbits,
-                                     FLAGS_cache_remove_scan_count_limit)
+                       ? NewLRUCache(FLAGS_cache_size, FLAGS_cache_numshardbits)
                        : NewLRUCache(FLAGS_cache_size))
                 : nullptr),
         compressed_cache_(FLAGS_compressed_cache_size >= 0

db/db_impl.cc

@@ -240,8 +240,7 @@ DBImpl::DBImpl(const DBOptions& options, const std::string& dbname)
         4194304 : db_options_.max_open_files - 10;
   // Reserve ten files or so for other uses and give the rest to TableCache.
   table_cache_ =
-      NewLRUCache(table_cache_size, db_options_.table_cache_numshardbits,
-                  db_options_.table_cache_remove_scan_count_limit);
+      NewLRUCache(table_cache_size, db_options_.table_cache_numshardbits);
 
   versions_.reset(new VersionSet(dbname_, &db_options_, env_options_,
                                  table_cache_.get(), &write_buffer_,

db/flush_job_test.cc

@@ -25,7 +25,7 @@ class FlushJobTest : public testing::Test {
   FlushJobTest()
       : env_(Env::Default()),
         dbname_(test::TmpDir() + "/flush_job_test"),
-        table_cache_(NewLRUCache(50000, 16, 8)),
+        table_cache_(NewLRUCache(50000, 16)),
         write_buffer_(db_options_.db_write_buffer_size),
         versions_(new VersionSet(dbname_, &db_options_, env_options_,
                                  table_cache_.get(), &write_buffer_,

db/repair.cc

@@ -69,8 +69,7 @@ class Repairer {
         raw_table_cache_(
             // TableCache can be small since we expect each table to be opened
             // once.
-            NewLRUCache(10, options_.table_cache_numshardbits,
-                        options_.table_cache_remove_scan_count_limit)),
+            NewLRUCache(10, options_.table_cache_numshardbits)),
         next_file_number_(1) {
     table_cache_ =
         new TableCache(ioptions_, env_options_, raw_table_cache_.get());

db/version_set.cc

@@ -2370,9 +2370,8 @@ Status VersionSet::ReduceNumberOfLevels(const std::string& dbname,
   }
 
   ColumnFamilyOptions cf_options(*options);
-  std::shared_ptr<Cache> tc(NewLRUCache(
-      options->max_open_files - 10, options->table_cache_numshardbits,
-      options->table_cache_remove_scan_count_limit));
+  std::shared_ptr<Cache> tc(NewLRUCache(options->max_open_files - 10,
+                                        options->table_cache_numshardbits));
   WriteController wc;
   WriteBuffer wb(options->db_write_buffer_size);
   VersionSet versions(dbname, options, env_options, tc.get(), &wb, &wc);

db/wal_manager_test.cc

@@ -28,7 +28,7 @@ class WalManagerTest : public testing::Test {
   WalManagerTest()
       : env_(Env::Default()),
         dbname_(test::TmpDir() + "/wal_manager_test"),
-        table_cache_(NewLRUCache(50000, 16, 8)),
+        table_cache_(NewLRUCache(50000, 16)),
         write_buffer_(db_options_.db_write_buffer_size),
         current_log_number_(0) {
     DestroyDB(dbname_, Options());

include/rocksdb/cache.h

@@ -34,20 +34,11 @@ class Cache;
 
 // Create a new cache with a fixed size capacity. The cache is sharded
 // to 2^numShardBits shards, by hash of the key. The total capacity
-// is divided and evenly assigned to each shard. Inside each shard,
-// the eviction is done in two passes: first try to free spaces by
-// evicting entries that are among the most least used removeScanCountLimit
-// entries and do not have reference other than by the cache itself, in
-// the least-used order. If not enough space is freed, further free the
-// entries in least used order.
+// is divided and evenly assigned to each shard.
 //
-// The functions without parameter numShardBits and/or removeScanCountLimit
-// use default values. removeScanCountLimit's default value is 0, which
-// means a strict LRU order inside each shard.
+// The functions without parameter numShardBits uses default value, which is 4
 extern shared_ptr<Cache> NewLRUCache(size_t capacity);
 extern shared_ptr<Cache> NewLRUCache(size_t capacity, int numShardBits);
-extern shared_ptr<Cache> NewLRUCache(size_t capacity, int numShardBits,
-                                     int removeScanCountLimit);
 
 class Cache {
  public:

include/rocksdb/options.h

@@ -897,14 +897,8 @@ struct DBOptions {
   // Number of shards used for table cache.
   int table_cache_numshardbits;
 
-  // During data eviction of table's LRU cache, it would be inefficient
-  // to strictly follow LRU because this piece of memory will not really
-  // be released unless its refcount falls to zero. Instead, make two
-  // passes: the first pass will release items with refcount = 1,
-  // and if not enough space releases after scanning the number of
-  // elements specified by this parameter, we will remove items in LRU
-  // order.
-  int table_cache_remove_scan_count_limit;
+  // DEPRECATED
+  // int table_cache_remove_scan_count_limit;
 
   // The following two fields affect how archived logs will be deleted.
   // 1. If both set to 0, logs will be deleted asap and will not get into

java/rocksjni/options.cc

@@ -702,8 +702,8 @@ void Java_org_rocksdb_Options_setTableCacheNumshardbits(
  */
 jint Java_org_rocksdb_Options_tableCacheRemoveScanCountLimit(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  return reinterpret_cast<rocksdb::Options*>(
-      jhandle)->table_cache_remove_scan_count_limit;
+  // deprecated
+  return 0;
 }
 
 /*
@@ -713,8 +713,7 @@ jint Java_org_rocksdb_Options_tableCacheRemoveScanCountLimit(
  */
 void Java_org_rocksdb_Options_setTableCacheRemoveScanCountLimit(
     JNIEnv* env, jobject jobj, jlong jhandle, jint limit) {
-  reinterpret_cast<rocksdb::Options*>(
-      jhandle)->table_cache_remove_scan_count_limit = static_cast<int>(limit);
+  // deprecated
 }
 
 /*
@@ -3383,8 +3382,7 @@ jint Java_org_rocksdb_DBOptions_tableCacheNumshardbits(
  */
 void Java_org_rocksdb_DBOptions_setTableCacheRemoveScanCountLimit(
     JNIEnv* env, jobject jobj, jlong jhandle, jint limit) {
-  reinterpret_cast<rocksdb::DBOptions*>(
-      jhandle)->table_cache_remove_scan_count_limit = static_cast<int>(limit);
+  // deprecated
 }
 
 /*
@@ -3394,8 +3392,8 @@ void Java_org_rocksdb_DBOptions_setTableCacheRemoveScanCountLimit(
  */
 jint Java_org_rocksdb_DBOptions_tableCacheRemoveScanCountLimit(
     JNIEnv* env, jobject jobj, jlong jhandle) {
-  return reinterpret_cast<rocksdb::DBOptions*>(
-      jhandle)->table_cache_remove_scan_count_limit;
+  // deprecated
+  return 0;
 }
 
 /*

util/cache.cc

@@ -193,9 +193,6 @@ class LRUCache {
 
   // Separate from constructor so caller can easily make an array of LRUCache
   void SetCapacity(size_t capacity) { capacity_ = capacity; }
-  void SetRemoveScanCountLimit(uint32_t remove_scan_count_limit) {
-    remove_scan_count_limit_ = remove_scan_count_limit;
-  }
 
   // Like Cache methods, but with an extra "hash" parameter.
   Cache::Handle* Insert(const Slice& key, uint32_t hash,
@@ -224,7 +221,6 @@ class LRUCache {
 
   // Initialized before use.
   size_t capacity_;
-  uint32_t remove_scan_count_limit_;
 
   // mutex_ protects the following state.
   // We don't count mutex_ as the cache's internal state so semantically we
@@ -426,7 +422,6 @@ void LRUCache::Erase(const Slice& key, uint32_t hash) {
 }
 
 static int kNumShardBits = 4;          // default values, can be overridden
-static int kRemoveScanCountLimit = 0; // default values, can be overridden
 
 class ShardedLRUCache : public Cache {
  private:
@@ -445,28 +440,16 @@ class ShardedLRUCache : public Cache {
     return (num_shard_bits_ > 0) ? (hash >> (32 - num_shard_bits_)) : 0;
   }
 
-  void init(size_t capacity, int numbits, int removeScanCountLimit) {
-    num_shard_bits_ = numbits;
-    capacity_ = capacity;
+ public:
+  ShardedLRUCache(size_t capacity, int num_shard_bits)
+      : last_id_(0), num_shard_bits_(num_shard_bits), capacity_(capacity) {
     int num_shards = 1 << num_shard_bits_;
     shards_ = new LRUCache[num_shards];
     const size_t per_shard = (capacity + (num_shards - 1)) / num_shards;
     for (int s = 0; s < num_shards; s++) {
       shards_[s].SetCapacity(per_shard);
-      shards_[s].SetRemoveScanCountLimit(removeScanCountLimit);
     }
   }
-
- public:
-  explicit ShardedLRUCache(size_t capacity)
-      : last_id_(0) {
-    init(capacity, kNumShardBits, kRemoveScanCountLimit);
-  }
-  ShardedLRUCache(size_t capacity, int num_shard_bits,
-                  int removeScanCountLimit)
-     : last_id_(0) {
-    init(capacity, num_shard_bits, removeScanCountLimit);
-  }
   virtual ~ShardedLRUCache() {
     delete[] shards_;
   }
@@ -526,17 +509,10 @@ shared_ptr<Cache> NewLRUCache(size_t capacity) {
 }
 
 shared_ptr<Cache> NewLRUCache(size_t capacity, int num_shard_bits) {
-  return NewLRUCache(capacity, num_shard_bits, kRemoveScanCountLimit);
-}
-
-shared_ptr<Cache> NewLRUCache(size_t capacity, int num_shard_bits,
-                              int removeScanCountLimit) {
   if (num_shard_bits >= 20) {
     return nullptr;  // the cache cannot be sharded into too many fine pieces
   }
-  return std::make_shared<ShardedLRUCache>(capacity,
-                                           num_shard_bits,
-                                           removeScanCountLimit);
+  return std::make_shared<ShardedLRUCache>(capacity, num_shard_bits);
 }
 
 }  // namespace rocksdb

util/cache_test.cc

@@ -43,11 +43,9 @@ class CacheTest : public testing::Test {
 
   static const int kCacheSize = 1000;
   static const int kNumShardBits = 4;
-  static const int kRemoveScanCountLimit = 16;
 
   static const int kCacheSize2 = 100;
   static const int kNumShardBits2 = 2;
-  static const int kRemoveScanCountLimit2 = 200;
 
   std::vector<int> deleted_keys_;
   std::vector<int> deleted_values_;
@@ -55,9 +53,8 @@ class CacheTest : public testing::Test {
   shared_ptr<Cache> cache2_;
 
   CacheTest() :
-      cache_(NewLRUCache(kCacheSize, kNumShardBits, kRemoveScanCountLimit)),
-      cache2_(NewLRUCache(kCacheSize2, kNumShardBits2,
-                          kRemoveScanCountLimit2)) {
+      cache_(NewLRUCache(kCacheSize, kNumShardBits)),
+      cache2_(NewLRUCache(kCacheSize2, kNumShardBits2)) {
     current_ = this;
   }
 
@@ -116,7 +113,7 @@ void dumbDeleter(const Slice& key, void* value) { }
 TEST_F(CacheTest, UsageTest) {
   // cache is shared_ptr and will be automatically cleaned up.
   const uint64_t kCapacity = 100000;
-  auto cache = NewLRUCache(kCapacity, 8, 200);
+  auto cache = NewLRUCache(kCapacity, 8);
 
   size_t usage = 0;
   const char* value = "abcdef";

util/ldb_cmd.cc

@@ -525,9 +525,8 @@ void DumpManifestFile(std::string file, bool verbose, bool hex) {
   Options options;
   EnvOptions sopt;
   std::string dbname("dummy");
-  std::shared_ptr<Cache> tc(
-      NewLRUCache(options.max_open_files - 10, options.table_cache_numshardbits,
-                  options.table_cache_remove_scan_count_limit));
+  std::shared_ptr<Cache> tc(NewLRUCache(options.max_open_files - 10,
+                                        options.table_cache_numshardbits));
   // Notice we are using the default options not through SanitizeOptions(),
   // if VersionSet::DumpManifest() depends on any option done by
   // SanitizeOptions(), we need to initialize it manually.
@@ -1134,8 +1133,7 @@ Status ReduceDBLevelsCommand::GetOldNumOfLevels(Options& opt,
     int* levels) {
   EnvOptions soptions;
   std::shared_ptr<Cache> tc(
-      NewLRUCache(opt.max_open_files - 10, opt.table_cache_numshardbits,
-                  opt.table_cache_remove_scan_count_limit));
+      NewLRUCache(opt.max_open_files - 10, opt.table_cache_numshardbits));
   const InternalKeyComparator cmp(opt.comparator);
   WriteController wc;
   WriteBuffer wb(opt.db_write_buffer_size);

util/options.cc

@@ -238,7 +238,6 @@ DBOptions::DBOptions()
       keep_log_file_num(1000),
       max_manifest_file_size(std::numeric_limits<uint64_t>::max()),
       table_cache_numshardbits(4),
-      table_cache_remove_scan_count_limit(16),
       WAL_ttl_seconds(0),
       WAL_size_limit_MB(0),
       manifest_preallocation_size(4 * 1024 * 1024),
@@ -282,8 +281,6 @@ DBOptions::DBOptions(const Options& options)
       keep_log_file_num(options.keep_log_file_num),
       max_manifest_file_size(options.max_manifest_file_size),
       table_cache_numshardbits(options.table_cache_numshardbits),
-      table_cache_remove_scan_count_limit(
-          options.table_cache_remove_scan_count_limit),
       WAL_ttl_seconds(options.WAL_ttl_seconds),
       WAL_size_limit_MB(options.WAL_size_limit_MB),
       manifest_preallocation_size(options.manifest_preallocation_size),
@@ -330,8 +327,6 @@ void DBOptions::Dump(Logger* log) const {
         wal_dir.c_str());
     Log(log, "               Options.table_cache_numshardbits: %d",
         table_cache_numshardbits);
-    Log(log, "    Options.table_cache_remove_scan_count_limit: %d",
-        table_cache_remove_scan_count_limit);
     Log(log, "    Options.delete_obsolete_files_period_micros: %" PRIu64,
         delete_obsolete_files_period_micros);
     Log(log, "             Options.max_background_compactions: %d",

util/options_helper.cc

@@ -509,8 +509,6 @@ bool ParseDBOption(const std::string& name, const std::string& value,
       new_options->max_manifest_file_size = ParseUint64(value);
     } else if (name == "table_cache_numshardbits") {
       new_options->table_cache_numshardbits = ParseInt(value);
-    } else if (name == "table_cache_remove_scan_count_limit") {
-      new_options->table_cache_remove_scan_count_limit = ParseInt(value);
     } else if (name == "WAL_ttl_seconds") {
       new_options->WAL_ttl_seconds = ParseUint64(value);
     } else if (name == "WAL_size_limit_MB") {

util/options_test.cc

@@ -159,7 +159,6 @@ TEST_F(OptionsTest, GetOptionsFromMapTest) {
     {"keep_log_file_num", "39"},
     {"max_manifest_file_size", "40"},
     {"table_cache_numshardbits", "41"},
-    {"table_cache_remove_scan_count_limit", "42"},
     {"WAL_ttl_seconds", "43"},
     {"WAL_size_limit_MB", "44"},
     {"manifest_preallocation_size", "45"},
@@ -266,7 +265,6 @@ TEST_F(OptionsTest, GetOptionsFromMapTest) {
   ASSERT_EQ(new_db_opt.keep_log_file_num, 39U);
   ASSERT_EQ(new_db_opt.max_manifest_file_size, static_cast<uint64_t>(40));
   ASSERT_EQ(new_db_opt.table_cache_numshardbits, 41);
-  ASSERT_EQ(new_db_opt.table_cache_remove_scan_count_limit, 42);
   ASSERT_EQ(new_db_opt.WAL_ttl_seconds, static_cast<uint64_t>(43));
   ASSERT_EQ(new_db_opt.WAL_size_limit_MB, static_cast<uint64_t>(44));
   ASSERT_EQ(new_db_opt.manifest_preallocation_size, 45U);