Optimize stale slot shrinking for previously cleaned roots (#10099)

* Prioritize shrinking of previously cleaned roots

* measure time of stale slot shrinking

* Disable shrink for test

* shrink: budgeting, store count, force for snapshot

* Polish implementation and fix tests

* Fix ci..

* Clean up a bit

* Further polish implementation and fix/add tests

* Rebase fixes

* Remove unneeded Default for AccountStorageEntry

* Address review comments

* More cleanup

* More cleanup

core/src/accounts_background_service.rs

@@ -15,11 +15,15 @@ pub struct AccountsBackgroundService {
 }
 
 const INTERVAL_MS: u64 = 100;
+const SHRUNKEN_ACCOUNT_PER_SEC: usize = 250;
+const SHRUNKEN_ACCOUNT_PER_INTERVAL: usize =
+    SHRUNKEN_ACCOUNT_PER_SEC / (1000 / INTERVAL_MS as usize);
 
 impl AccountsBackgroundService {
     pub fn new(bank_forks: Arc<RwLock<BankForks>>, exit: &Arc<AtomicBool>) -> Self {
         info!("AccountsBackgroundService active");
         let exit = exit.clone();
+        let mut consumed_budget = 0;
         let t_background = Builder::new()
             .name("solana-accounts-background".to_string())
             .spawn(move || loop {
@@ -30,8 +34,8 @@ impl AccountsBackgroundService {
 
                 bank.process_dead_slots();
 
-                // Currently, given INTERVAL_MS, we process 1 slot/100 ms
-                bank.process_stale_slot();
+                consumed_budget = bank
+                    .process_stale_slot_with_budget(consumed_budget, SHRUNKEN_ACCOUNT_PER_INTERVAL);
 
                 sleep(Duration::from_millis(INTERVAL_MS));
             })