EVM-899: Skip write when no change (#709)

* EVM-899: Don't even call the HAMT store if there was no change.

* EVM-899: Measurement updates with flush fix.

actors/evm/src/interpreter/system.rs

@@ -46,9 +46,6 @@ impl<'r, BS: Blockstore, RT: Runtime<BS>> System<'r, BS, RT> {
 
     /// Get value of a storage key.
     pub fn get_storage(&mut self, key: U256) -> Result<Option<U256>, StatusCode> {
-        let mut key_bytes = [0u8; 32];
-        key.to_big_endian(&mut key_bytes);
-
         Ok(self.state.get(&key).map_err(|e| StatusCode::InternalError(e.to_string()))?.cloned())
     }
 
@@ -58,24 +55,23 @@ impl<'r, BS: Blockstore, RT: Runtime<BS>> System<'r, BS, RT> {
         key: U256,
         value: Option<U256>,
     ) -> Result<StorageStatus, StatusCode> {
-        let mut key_bytes = [0u8; 32];
-        key.to_big_endian(&mut key_bytes);
-
-        let prev_value =
-            self.state.get(&key).map_err(|e| StatusCode::InternalError(e.to_string()))?.cloned();
+        let prev_value = self.get_storage(key)?;
 
-        let mut storage_status =
-            if prev_value == value { StorageStatus::Unchanged } else { StorageStatus::Modified };
-
-        if value.is_none() {
-            self.state.delete(&key).map_err(|e| StatusCode::InternalError(e.to_string()))?;
-            storage_status = StorageStatus::Deleted;
-        } else {
-            self.state
-                .set(key, value.unwrap())
-                .map_err(|e| StatusCode::InternalError(e.to_string()))?;
+        match (prev_value, value) {
+            (None, None) => Ok(StorageStatus::Unchanged),
+            (Some(_), None) => {
+                self.state.delete(&key).map_err(|e| StatusCode::InternalError(e.to_string()))?;
+                Ok(StorageStatus::Deleted)
+            }
+            (Some(p), Some(n)) if p == n => Ok(StorageStatus::Unchanged),
+            (_, Some(v)) => {
+                self.state.set(key, v).map_err(|e| StatusCode::InternalError(e.to_string()))?;
+                if prev_value.is_none() {
+                    Ok(StorageStatus::Added)
+                } else {
+                    Ok(StorageStatus::Modified)
+                }
+            }
         }
-
-        Ok(storage_status)
     }
 }

actors/evm/tests/measurements/mapping_add_n1.jsonline

@@ -1,4 +1,4 @@
-{"i":0,"series":1,"stats":{"get_bytes":2185,"get_count":4,"put_bytes":2188,"put_count":5}}
+{"i":0,"series":1,"stats":{"get_bytes":2185,"get_count":4,"put_bytes":2185,"put_count":4}}
 {"i":1,"series":1,"stats":{"get_bytes":2185,"get_count":4,"put_bytes":180,"put_count":2}}
 {"i":2,"series":1,"stats":{"get_bytes":2275,"get_count":4,"put_bytes":261,"put_count":2}}
 {"i":3,"series":1,"stats":{"get_bytes":2356,"get_count":4,"put_bytes":345,"put_count":2}}
@@ -98,7 +98,7 @@
 {"i":97,"series":1,"stats":{"get_bytes":9383,"get_count":4,"put_bytes":7362,"put_count":2}}
 {"i":98,"series":1,"stats":{"get_bytes":9457,"get_count":4,"put_bytes":7437,"put_count":2}}
 {"i":99,"series":1,"stats":{"get_bytes":9532,"get_count":4,"put_bytes":7511,"put_count":2}}
-{"i":0,"series":2,"stats":{"get_bytes":9606,"get_count":4,"put_bytes":7511,"put_count":2}}
+{"i":0,"series":2,"stats":{"get_bytes":9606,"get_count":4,"put_bytes":87,"put_count":1}}
 {"i":1,"series":2,"stats":{"get_bytes":9606,"get_count":4,"put_bytes":7585,"put_count":2}}
 {"i":2,"series":2,"stats":{"get_bytes":9680,"get_count":4,"put_bytes":7658,"put_count":2}}
 {"i":3,"series":2,"stats":{"get_bytes":9753,"get_count":4,"put_bytes":7732,"put_count":2}}

actors/evm/tests/measurements/mapping_add_n100.jsonline

@@ -1,4 +1,4 @@
-{"i":0,"series":1,"stats":{"get_bytes":2185,"get_count":4,"put_bytes":2188,"put_count":5}}
+{"i":0,"series":1,"stats":{"get_bytes":2185,"get_count":4,"put_bytes":2185,"put_count":4}}
 {"i":1,"series":1,"stats":{"get_bytes":2185,"get_count":4,"put_bytes":7494,"put_count":2}}
 {"i":2,"series":1,"stats":{"get_bytes":9589,"get_count":4,"put_bytes":15001,"put_count":4}}
 {"i":3,"series":1,"stats":{"get_bytes":16765,"get_count":5,"put_bytes":22582,"put_count":11}}
@@ -98,7 +98,7 @@
 {"i":97,"series":1,"stats":{"get_bytes":254250,"get_count":88,"put_bytes":259638,"put_count":86}}
 {"i":98,"series":1,"stats":{"get_bytes":245365,"get_count":83,"put_bytes":250747,"put_count":81}}
 {"i":99,"series":1,"stats":{"get_bytes":265670,"get_count":91,"put_bytes":271053,"put_count":89}}
-{"i":0,"series":2,"stats":{"get_bytes":262559,"get_count":87,"put_bytes":11133,"put_count":2}}
+{"i":0,"series":2,"stats":{"get_bytes":262559,"get_count":87,"put_bytes":87,"put_count":1}}
 {"i":1,"series":2,"stats":{"get_bytes":256304,"get_count":86,"put_bytes":261594,"put_count":84}}
 {"i":2,"series":2,"stats":{"get_bytes":259549,"get_count":88,"put_bytes":264832,"put_count":86}}
 {"i":3,"series":2,"stats":{"get_bytes":258453,"get_count":87,"put_bytes":263745,"put_count":85}}