i/o stats for backend databases (#4525)

substrate/client/src/client.rs

@@ -1176,7 +1176,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 	pub fn usage_info(&self) -> ClientInfo<Block> {
 		ClientInfo {
 			chain: self.chain_info(),
-			used_state_cache_size: self.backend.used_state_cache_size(),
+			usage: self.backend.usage_info(),
 		}
 	}
 

substrate/client/src/in_mem.rs

@@ -37,6 +37,7 @@ use sc_client_api::{
 	blockchain::{
 		self, BlockStatus, HeaderBackend, well_known_cache_keys::Id as CacheKeyId
 	},
+	UsageInfo,
 };
 use crate::leaves::LeafSet;
 
@@ -449,6 +450,10 @@ impl<Block: BlockT> sc_client_api::light::Storage<Block> for Blockchain<Block>
 	fn cache(&self) -> Option<Arc<dyn blockchain::Cache<Block>>> {
 		None
 	}
+
+	fn usage_info(&self) -> Option<sc_client_api::UsageInfo> {
+		None
+	}
 }
 
 /// In-memory operation.
@@ -681,7 +686,7 @@ where
 		&self.blockchain
 	}
 
-	fn used_state_cache_size(&self) -> Option<usize> {
+	fn usage_info(&self) -> Option<UsageInfo> {
 		None
 	}
 

substrate/client/src/light/backend.rs

@@ -39,6 +39,7 @@ use sc_client_api::{
 		HeaderBackend as BlockchainHeaderBackend, well_known_cache_keys,
 	},
 	light::Storage as BlockchainStorage,
+	UsageInfo,
 };
 use crate::light::blockchain::Blockchain;
 use hash_db::Hasher;
@@ -186,8 +187,8 @@ impl<S, Block, H> ClientBackend<Block, H> for Backend<S, H> where
 		&self.blockchain
 	}
 
-	fn used_state_cache_size(&self) -> Option<usize> {
-		None
+	fn usage_info(&self) -> Option<UsageInfo> {
+		self.blockchain.storage().usage_info()
 	}
 
 	fn changes_trie_storage(&self) -> Option<&Self::ChangesTrieStorage> {

substrate/client/src/light/blockchain.rs

@@ -314,5 +314,9 @@ pub mod tests {
 		fn cache(&self) -> Option<Arc<dyn BlockchainCache<Block>>> {
 			None
 		}
+
+		fn usage_info(&self) -> Option<sc_client_api::UsageInfo> {
+			None
+		}
 	}
 }