Drain the entire compute budget (#12478)

programs/bpf/benches/bpf_loader.rs

@@ -286,8 +286,9 @@ pub struct MockComputeMeter {
 }
 impl ComputeMeter for MockComputeMeter {
     fn consume(&mut self, amount: u64) -> Result<(), InstructionError> {
+        let exceeded = self.remaining < amount;
         self.remaining = self.remaining.saturating_sub(amount);
-        if self.remaining == 0 {
+        if exceeded {
             return Err(InstructionError::ComputationalBudgetExceeded);
         }
         Ok(())

programs/bpf_loader/src/lib.rs

@@ -287,8 +287,9 @@ mod tests {
     }
     impl ComputeMeter for MockComputeMeter {
         fn consume(&mut self, amount: u64) -> Result<(), InstructionError> {
+            let exceeded = self.remaining < amount;
             self.remaining = self.remaining.saturating_sub(amount);
-            if self.remaining == 0 {
+            if exceeded {
                 return Err(InstructionError::ComputationalBudgetExceeded);
             }
             Ok(())

programs/bpf_loader/src/syscalls.rs

@@ -1269,7 +1269,7 @@ mod tests {
         let addr = string.as_ptr() as *const _ as u64;
 
         let compute_meter: Rc<RefCell<dyn ComputeMeter>> =
-            Rc::new(RefCell::new(MockComputeMeter { remaining: 4 }));
+            Rc::new(RefCell::new(MockComputeMeter { remaining: 3 }));
         let log = Rc::new(RefCell::new(vec![]));
         let logger: Rc<RefCell<dyn Logger>> =
             Rc::new(RefCell::new(MockLogger { log: log.clone() }));

runtime/src/message_processor.rs

@@ -187,8 +187,9 @@ pub struct ThisComputeMeter {
 }
 impl ComputeMeter for ThisComputeMeter {
     fn consume(&mut self, amount: u64) -> Result<(), InstructionError> {
+        let exceeded = self.remaining < amount;
         self.remaining = self.remaining.saturating_sub(amount);
-        if self.remaining == 0 {
+        if exceeded {
             return Err(InstructionError::ComputationalBudgetExceeded);
         }
         Ok(())