--amend

(cherry picked from commit ad3cb0b)

runtime/src/bank.rs

@@ -361,7 +361,7 @@ struct CachedExecutorsEntry {
 struct CachedExecutors {
     max: usize,
     current_epoch: Epoch,
-    executors: HashMap<Pubkey, CachedExecutorsEntry>,
+    pub(self) executors: HashMap<Pubkey, CachedExecutorsEntry>,
     stats: executor_cache::Stats,
 }
 impl Default for CachedExecutors {
@@ -12007,6 +12007,35 @@ pub(crate) mod tests {
         assert!(cache.get(&key3).is_some());
     }
 
+    #[test]
+    fn test_cached_executors_evicts_smallest() {
+        let key1 = solana_sdk::pubkey::new_rand();
+        let key2 = solana_sdk::pubkey::new_rand();
+        let key3 = solana_sdk::pubkey::new_rand();
+        let executor: Arc<dyn Executor> = Arc::new(TestExecutor {});
+        let mut cache = CachedExecutors::new(2, 0);
+
+        cache.put(&key1, executor.clone());
+        for _ in 0..5 {
+            let _ = cache.get(&key1);
+        }
+        cache.put(&key2, executor.clone());
+        // make key1's use-count for sure greater than key2's
+        let _ = cache.get(&key1);
+
+        let mut entries = cache
+            .executors
+            .iter()
+            .map(|(k, v)| (*k, v.epoch_count.load(Relaxed)))
+            .collect::<Vec<_>>();
+        entries.sort_by_key(|(_, v)| *v);
+        assert!(entries[0].1 < entries[1].1);
+
+        cache.put(&key3, executor.clone());
+        assert!(cache.get(&entries[0].0).is_none());
+        assert!(cache.get(&entries[1].0).is_some());
+    }
+
     #[test]
     fn test_bank_executor_cache() {
         solana_logger::setup();