feature gate on removing unwanted rounding

core/src/banking_stage/consumer.rs

@@ -747,6 +747,8 @@ impl Consumer {
             bank.feature_set.is_active(
                 &feature_set::include_loaded_accounts_data_size_in_fee_calculation::id(),
             ),
+            bank.feature_set
+                .is_active(&feature_set::remove_rounding_in_fee_calculation::id()),
         );
         let (mut fee_payer_account, _slot) = bank
             .rc

core/src/banking_stage/transaction_scheduler/scheduler_controller.rs

@@ -25,8 +25,13 @@ use {
     solana_runtime::{bank::Bank, bank_forks::BankForks},
     solana_sdk::{
         clock::MAX_PROCESSING_AGE,
-        feature_set::include_loaded_accounts_data_size_in_fee_calculation, fee::FeeBudgetLimits,
-        saturating_add_assign, transaction::SanitizedTransaction,
+        feature_set::{
+            include_loaded_accounts_data_size_in_fee_calculation,
+            remove_rounding_in_fee_calculation,
+        },
+        fee::FeeBudgetLimits,
+        saturating_add_assign,
+        transaction::SanitizedTransaction,
     },
     solana_svm::transaction_error_metrics::TransactionErrorMetrics,
     std::{
@@ -422,6 +427,8 @@ impl SchedulerController {
             fee_budget_limits,
             bank.feature_set
                 .is_active(&include_loaded_accounts_data_size_in_fee_calculation::id()),
+            bank.feature_set
+                .is_active(&remove_rounding_in_fee_calculation::id()),
         );
 
         // We need a multiplier here to avoid rounding down too aggressively.

programs/sbf/tests/programs.rs

@@ -3713,6 +3713,7 @@ fn test_program_fees() {
             .unwrap_or_default()
             .into(),
         false,
+        true,
     );
     bank_client
         .send_and_confirm_message(&[&mint_keypair], message)
@@ -3736,6 +3737,7 @@ fn test_program_fees() {
             .unwrap_or_default()
             .into(),
         false,
+        true,
     );
     assert!(expected_normal_fee < expected_prioritized_fee);
 

runtime/src/bank.rs

@@ -117,7 +117,10 @@ use {
         epoch_info::EpochInfo,
         epoch_schedule::EpochSchedule,
         feature,
-        feature_set::{self, include_loaded_accounts_data_size_in_fee_calculation, FeatureSet},
+        feature_set::{
+            self, include_loaded_accounts_data_size_in_fee_calculation,
+            remove_rounding_in_fee_calculation, FeatureSet,
+        },
         fee::FeeStructure,
         fee_calculator::{FeeCalculator, FeeRateGovernor},
         genesis_config::{ClusterType, GenesisConfig},
@@ -4016,6 +4019,8 @@ impl Bank {
                 .into(),
             self.feature_set
                 .is_active(&include_loaded_accounts_data_size_in_fee_calculation::id()),
+            self.feature_set
+                .is_active(&remove_rounding_in_fee_calculation::id()),
         )
     }
 

runtime/src/bank/tests.rs

@@ -10031,7 +10031,7 @@ fn calculate_test_fee(
         .unwrap_or_default()
         .into();
 
-    fee_structure.calculate_fee(message, lamports_per_signature, &budget_limits, false)
+    fee_structure.calculate_fee(message, lamports_per_signature, &budget_limits, false, true)
 }
 
 #[test]

sdk/src/feature_set.rs

@@ -780,6 +780,10 @@ pub mod enable_chained_merkle_shreds {
     solana_sdk::declare_id!("7uZBkJXJ1HkuP6R3MJfZs7mLwymBcDbKdqbF51ZWLier");
 }
 
+pub mod remove_rounding_in_fee_calculation {
+    solana_sdk::declare_id!("BtVN7YjDzNE6Dk7kTT7YTDgMNUZTNgiSJgsdzAeTg2jF");
+}
+
 lazy_static! {
     /// Map of feature identifiers to user-visible description
     pub static ref FEATURE_NAMES: HashMap<Pubkey, &'static str> = [
@@ -970,6 +974,7 @@ lazy_static! {
         (cost_model_requested_write_lock_cost::id(), "cost model uses number of requested write locks #34819"),
         (enable_gossip_duplicate_proof_ingestion::id(), "enable gossip duplicate proof ingestion #32963"),
         (enable_chained_merkle_shreds::id(), "Enable chained Merkle shreds #34916"),
+        (remove_rounding_in_fee_calculation::id(), "Removing unwanted rounding in fee calculation #34982"),
         /*************** ADD NEW FEATURES HERE ***************/
     ]
     .iter()

sdk/src/fee.rs

@@ -38,8 +38,14 @@ pub struct FeeDetails {
 }
 
 impl FeeDetails {
-    pub fn total_fee(&self) -> u64 {
-        self.transaction_fee.saturating_add(self.prioritization_fee)
+    pub fn total_fee(&self, remove_rounding_in_fee_calculation: bool) -> u64 {
+        let total_fee = self.transaction_fee.saturating_add(self.prioritization_fee);
+        if remove_rounding_in_fee_calculation {
+            total_fee
+        } else {
+            // backward compatible behavior
+            (total_fee as f64).round() as u64
+        }
     }
 }
 
@@ -95,6 +101,7 @@ impl FeeStructure {
         lamports_per_signature: u64,
         budget_limits: &FeeBudgetLimits,
         include_loaded_account_data_size_in_fee: bool,
+        remove_rounding_in_fee_calculation: bool,
     ) -> u64 {
         // Fee based on compute units and signatures
         let congestion_multiplier = if lamports_per_signature == 0 {
@@ -103,15 +110,13 @@ impl FeeStructure {
             1.0 // multiplier that has no effect
         };
 
-        (self
-            .calculate_fee_details(
-                message,
-                budget_limits,
-                include_loaded_account_data_size_in_fee,
-            )
-            .total_fee() as f64
-            * congestion_multiplier)
-            .round() as u64
+        self.calculate_fee_details(
+            message,
+            budget_limits,
+            include_loaded_account_data_size_in_fee,
+        )
+        .total_fee(remove_rounding_in_fee_calculation)
+        .saturating_mul(congestion_multiplier as u64)
     }
 
     /// Calculate fee details for `SanitizedMessage`
@@ -210,4 +215,19 @@ mod tests {
             FeeStructure::calculate_memory_usage_cost(64 * K, heap_cost)
         );
     }
+
+    #[test]
+    fn test_total_fee_rounding() {
+        // round large `f64` can lost precision, see feature gate:
+        // "Removing unwanted rounding in fee calculation #34982"
+
+        let large_fee_details = FeeDetails {
+            transaction_fee: u64::MAX - 11,
+            prioritization_fee: 1,
+        };
+        let expected_large_fee = u64::MAX - 10;
+
+        assert_eq!(large_fee_details.total_fee(true), expected_large_fee);
+        assert_ne!(large_fee_details.total_fee(false), expected_large_fee);
+    }
 }

svm/src/account_loader.rs

@@ -15,7 +15,10 @@ use {
             create_executable_meta, is_builtin, is_executable, Account, AccountSharedData,
             ReadableAccount, WritableAccount,
         },
-        feature_set::{self, include_loaded_accounts_data_size_in_fee_calculation},
+        feature_set::{
+            self, include_loaded_accounts_data_size_in_fee_calculation,
+            remove_rounding_in_fee_calculation,
+        },
         fee::FeeStructure,
         message::SanitizedMessage,
         native_loader,
@@ -74,6 +77,7 @@ pub fn load_accounts<CB: TransactionProcessingCallback>(
                         .into(),
                         feature_set
                             .is_active(&include_loaded_accounts_data_size_in_fee_calculation::id()),
+                        feature_set.is_active(&remove_rounding_in_fee_calculation::id()),
                     )
                 } else {
                     return (Err(TransactionError::BlockhashNotFound), None);
@@ -682,6 +686,7 @@ mod tests {
                 .unwrap_or_default()
                 .into(),
             false,
+            true,
         );
         assert_eq!(fee, lamports_per_signature);
 
@@ -1210,6 +1215,7 @@ mod tests {
                 .unwrap_or_default()
                 .into(),
             false,
+            true,
         );
         assert_eq!(fee, lamports_per_signature + prioritization_fee);