add Name() to Cache

Summary: preparation for detecting Cache type. If SimCache, we then may trigger some command like "setSimCapacity()" with setOptions()

Test Plan: make all check

Reviewers: yiwu, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D61953

include/rocksdb/cache.h

@@ -51,6 +51,9 @@ class Cache {
   // Opaque handle to an entry stored in the cache.
   struct Handle {};
 
+  // The type of the Cache
+  virtual const char* Name() const = 0;
+
   // Insert a mapping from key->value into the cache and assign it
   // the specified charge against the total cache capacity.
   // If strict_capacity_limit is true and cache reaches its full capacity,

include/rocksdb/utilities/sim_cache.h

@@ -33,6 +33,8 @@ class SimCache : public Cache {
 
   virtual ~SimCache() {}
 
+  virtual const char* Name() const override { return "SimCache"; }
+
   // returns the maximum configured capacity of the simcache for simulation
   virtual size_t GetSimCapacity() const = 0;
 

util/lru_cache.cc

@@ -528,6 +528,7 @@ class LRUCache : public ShardedCache {
 
   virtual ~LRUCache() { delete[] shards_; }
 
+  virtual const char* Name() const override { return "LRUCache"; }
   virtual CacheShard* GetShard(int shard) override {
     return reinterpret_cast<CacheShard*>(&shards_[shard]);
   }

util/sharded_cache.h

@@ -46,7 +46,7 @@ class ShardedCache : public Cache {
  public:
   ShardedCache(size_t capacity, int num_shard_bits, bool strict_capacity_limit);
   virtual ~ShardedCache() = default;
-
+  virtual const char* Name() const override = 0;
   virtual CacheShard* GetShard(int shard) = 0;
   virtual const CacheShard* GetShard(int shard) const = 0;
   virtual void* Value(Handle* handle) override = 0;