rent collector improvments (#6888)

* avoid account copying + pre-empt rent

* adding support for base rent

core/src/validator.rs

@@ -508,7 +508,7 @@ pub fn new_validator_for_tests() -> (Validator, ContactInfo, Keypair, PathBuf) {
         mut genesis_config,
         mint_keypair,
         voting_keypair,
-    } = create_genesis_config_with_leader(10_000, &contact_info.id, 42);
+    } = create_genesis_config_with_leader(1_000_000, &contact_info.id, 42);
     genesis_config
         .native_instruction_processors
         .push(solana_budget_program!());

core/tests/client.rs

@@ -23,7 +23,8 @@ fn test_rpc_client() {
     );
 
     assert_eq!(client.get_balance(&bob_pubkey).unwrap(), 0);
-    assert_eq!(client.get_balance(&alice.pubkey()).unwrap(), 10000);
+
+    assert_eq!(client.get_balance(&alice.pubkey()).unwrap(), 1_000_000);
 
     let (blockhash, _fee_calculator) = client.get_recent_blockhash().unwrap();
 
@@ -49,7 +50,7 @@ fn test_rpc_client() {
     assert!(confirmed_tx);
 
     assert_eq!(client.get_balance(&bob_pubkey).unwrap(), 20);
-    assert_eq!(client.get_balance(&alice.pubkey()).unwrap(), 9980);
+    assert_eq!(client.get_balance(&alice.pubkey()).unwrap(), 999980);
 
     server.close().unwrap();
     remove_dir_all(ledger_path).unwrap();

runtime/src/accounts.rs

@@ -114,7 +114,10 @@ impl Accounts {
                 .filter(|key| !message.program_ids().contains(key))
             {
                 let (account, rent) = AccountsDB::load(storage, ancestors, accounts_index, key)
-                    .and_then(|(account, _)| rent_collector.update(account))
+                    .and_then(|(mut account, _)| {
+                        let rent_due = rent_collector.update(&mut account);
+                        Some((account, rent_due))
+                    })
                     .unwrap_or_default();
 
                 accounts.push(account);

runtime/src/rent_collector.rs

@@ -33,9 +33,9 @@ impl RentCollector {
     // updates this account's lamports and status and returns
     //  the account rent collected, if any
     //
-    pub fn update(&self, mut account: Account) -> Option<(Account, u64)> {
-        if account.data.is_empty() || account.rent_epoch > self.epoch {
-            Some((account, 0))
+    pub fn update(&self, account: &mut Account) -> u64 {
+        if account.rent_epoch > self.epoch {
+            0
         } else {
             let slots_elapsed: u64 = (account.rent_epoch..=self.epoch)
                 .map(|epoch| self.epoch_schedule.get_slots_in_epoch(epoch + 1))
@@ -51,13 +51,15 @@ impl RentCollector {
                 if account.lamports > rent_due {
                     account.rent_epoch = self.epoch + 1;
                     account.lamports -= rent_due;
-                    Some((account, rent_due))
+                    rent_due
                 } else {
-                    None
+                    let rent_charged = account.lamports;
+                    *account = Account::default();
+                    rent_charged
                 }
             } else {
                 // maybe collect rent later, leave account alone
-                Some((account, 0))
+                0
             }
         }
     }

sdk/src/rent.rs

@@ -26,6 +26,9 @@ pub const DEFAULT_EXEMPTION_THRESHOLD: f64 = 2.0;
 /// default amount of rent to burn, as a fraction of std::u8::MAX
 pub const DEFAULT_BURN_PERCENT: u8 = ((50usize * std::u8::MAX as usize) / 100usize) as u8;
 
+/// default account storage over head for calculation of base rent
+pub const ACCOUNT_STORAGE_OVERHEAD: u64 = 128;
+
 impl Default for Rent {
     fn default() -> Self {
         Self {
@@ -40,7 +43,8 @@ impl Rent {
     /// minimum balance due for a given size Account::data.len()
     pub fn minimum_balance(&self, data_len: usize) -> u64 {
         let bytes = data_len as u64;
-        bytes * (self.exemption_threshold * self.lamports_per_byte_year as f64) as u64
+        (((ACCOUNT_STORAGE_OVERHEAD + bytes) * self.lamports_per_byte_year) as f64
+            * self.exemption_threshold) as u64
     }
 
     /// whether a given balance and data_len would be exempt
@@ -54,7 +58,9 @@ impl Rent {
             (0, true)
         } else {
             (
-                ((self.lamports_per_byte_year * data_len as u64) as f64 * years_elapsed) as u64,
+                ((self.lamports_per_byte_year * (data_len as u64 + ACCOUNT_STORAGE_OVERHEAD))
+                    as f64
+                    * years_elapsed) as u64,
                 false,
             )
         }
@@ -74,20 +80,45 @@ mod tests {
 
     #[test]
     fn test_due() {
-        let rent = Rent::default();
+        let default_rent = Rent::default();
 
         assert_eq!(
-            rent.due(0, 1, 1.0),
+            default_rent.due(0, 2, 1.2),
             (
-                DEFAULT_LAMPORTS_PER_BYTE_YEAR,
+                (((2 + ACCOUNT_STORAGE_OVERHEAD) * DEFAULT_LAMPORTS_PER_BYTE_YEAR) as f64 * 1.2)
+                    as u64,
                 DEFAULT_LAMPORTS_PER_BYTE_YEAR == 0
             )
         );
         assert_eq!(
-            rent.due(
-                DEFAULT_LAMPORTS_PER_BYTE_YEAR * DEFAULT_EXEMPTION_THRESHOLD as u64,
-                1,
-                1.0
+            default_rent.due(
+                (((2 + ACCOUNT_STORAGE_OVERHEAD) * DEFAULT_LAMPORTS_PER_BYTE_YEAR) as f64
+                    * DEFAULT_EXEMPTION_THRESHOLD) as u64,
+                2,
+                1.2
+            ),
+            (0, true)
+        );
+
+        let mut custom_rent = Rent::default();
+        custom_rent.lamports_per_byte_year = 5;
+        custom_rent.exemption_threshold = 2.5;
+
+        assert_eq!(
+            custom_rent.due(0, 2, 1.2),
+            (
+                (((2 + ACCOUNT_STORAGE_OVERHEAD) * custom_rent.lamports_per_byte_year) as f64 * 1.2)
+                    as u64,
+                false
+            )
+        );
+
+        assert_eq!(
+            custom_rent.due(
+                (((2 + ACCOUNT_STORAGE_OVERHEAD) * custom_rent.lamports_per_byte_year) as f64
+                    * custom_rent.exemption_threshold) as u64,
+                2,
+                1.2
             ),
             (0, true)
         );