Change the latest slot snapshot storage from VecDeque to Option

core/src/validator.rs

@@ -625,6 +625,7 @@ impl Validator {
             snapshot_request_sender,
             snapshot_request_receiver,
             accounts_package_sender,
+            latest_slot_snapshot_storages: None,
         };
         let pruned_banks_request_handler = PrunedBanksRequestHandler {
             pruned_banks_receiver,

core/tests/epoch_accounts_hash.rs

@@ -210,6 +210,7 @@ impl BackgroundServices {
             snapshot_request_sender,
             snapshot_request_receiver,
             accounts_package_sender,
+            latest_slot_snapshot_storages: None,
         };
         let pruned_banks_request_handler = PrunedBanksRequestHandler {
             pruned_banks_receiver,

core/tests/snapshots.rs

@@ -16,7 +16,7 @@ use {
             AbsRequestHandlers, AbsRequestSender, AccountsBackgroundService,
             PrunedBanksRequestHandler, SnapshotRequestHandler,
         },
-        accounts_db::{self, SnapshotStorages, ACCOUNTS_DB_CONFIG_FOR_TESTING},
+        accounts_db::{self, ACCOUNTS_DB_CONFIG_FOR_TESTING},
         accounts_hash::AccountsHash,
         accounts_index::AccountSecondaryIndexes,
         bank::{Bank, BankSlotDelta},
@@ -51,7 +51,7 @@ use {
     },
     solana_streamer::socket::SocketAddrSpace,
     std::{
-        collections::{HashSet, VecDeque},
+        collections::HashSet,
         fs,
         io::{Error, ErrorKind},
         path::PathBuf,
@@ -234,13 +234,13 @@ fn run_bank_forks_snapshot_n<F>(
 
     let (snapshot_request_sender, snapshot_request_receiver) = unbounded();
     let request_sender = AbsRequestSender::new(snapshot_request_sender.clone());
-    let snapshot_request_handler = SnapshotRequestHandler {
+    let mut snapshot_request_handler = SnapshotRequestHandler {
         snapshot_config: snapshot_test_config.snapshot_config.clone(),
         snapshot_request_sender,
         snapshot_request_receiver,
         accounts_package_sender,
+        latest_slot_snapshot_storages: None,
     };
-    let mut snapshot_slot_storages: VecDeque<SnapshotStorages> = VecDeque::new();
     for slot in 1..=last_slot {
         let mut bank = Bank::new_from_parent(&bank_forks[slot - 1], &Pubkey::default(), slot);
         f(&mut bank, mint_keypair);
@@ -252,12 +252,7 @@ fn run_bank_forks_snapshot_n<F>(
             // set_root should send a snapshot request
             bank_forks.set_root(bank.slot(), &request_sender, None);
             bank.update_accounts_hash_for_tests();
-            snapshot_request_handler.handle_snapshot_requests(
-                false,
-                0,
-                &mut None,
-                &mut snapshot_slot_storages,
-            );
+            snapshot_request_handler.handle_snapshot_requests(false, 0, &mut None);
         }
     }
 
@@ -755,15 +750,15 @@ fn test_bank_forks_incremental_snapshot(
 
     let (snapshot_request_sender, snapshot_request_receiver) = unbounded();
     let request_sender = AbsRequestSender::new(snapshot_request_sender.clone());
-    let snapshot_request_handler = SnapshotRequestHandler {
+    let mut snapshot_request_handler = SnapshotRequestHandler {
         snapshot_config: snapshot_test_config.snapshot_config.clone(),
         snapshot_request_sender,
         snapshot_request_receiver,
         accounts_package_sender,
+        latest_slot_snapshot_storages: None,
     };
 
     let mut last_full_snapshot_slot = None;
-    let mut snapshot_slot_storages: VecDeque<SnapshotStorages> = VecDeque::new();
     for slot in 1..=LAST_SLOT {
         // Make a new bank and perform some transactions
         let bank = {
@@ -795,7 +790,6 @@ fn test_bank_forks_incremental_snapshot(
                 false,
                 0,
                 &mut last_full_snapshot_slot,
-                &mut snapshot_slot_storages,
             );
         }
 
@@ -1017,6 +1011,7 @@ fn test_snapshots_with_background_services(
         snapshot_request_sender,
         snapshot_request_receiver,
         accounts_package_sender: accounts_package_sender.clone(),
+        latest_slot_snapshot_storages: None,
     };
     let pruned_banks_request_handler = PrunedBanksRequestHandler {
         pruned_banks_receiver,

ledger-tool/src/main.rs

@@ -1138,6 +1138,7 @@ fn load_bank_forks(
         snapshot_request_sender,
         snapshot_request_receiver,
         accounts_package_sender,
+        latest_slot_snapshot_storages: None,
     };
     let pruned_banks_receiver =
         AccountsBackgroundService::setup_bank_drop_callback(bank_forks.clone());

runtime/src/accounts_background_service.rs

@@ -2,8 +2,6 @@
 //!
 //! This can be expensive since we have to walk the append vecs being cleaned up.
 
-use std::collections::VecDeque;
-
 mod stats;
 use {
     crate::{
@@ -141,16 +139,16 @@ pub struct SnapshotRequestHandler {
     pub snapshot_request_sender: SnapshotRequestSender,
     pub snapshot_request_receiver: SnapshotRequestReceiver,
     pub accounts_package_sender: Sender<AccountsPackage>,
+    pub latest_slot_snapshot_storages: Option<SnapshotStorages>,
 }
 
 impl SnapshotRequestHandler {
     // Returns the latest requested snapshot slot, if one exists
     pub fn handle_snapshot_requests(
-        &self,
+        &mut self,
         test_hash_calculation: bool,
         non_snapshot_time_us: u128,
         last_full_snapshot_slot: &mut Option<Slot>,
-        snapshot_slot_storages: &mut VecDeque<SnapshotStorages>,
     ) -> Option<Result<u64, SnapshotError>> {
         let (
             snapshot_request,
@@ -184,7 +182,6 @@ impl SnapshotRequestHandler {
             last_full_snapshot_slot,
             snapshot_request,
             accounts_package_type,
-            snapshot_slot_storages,
         ))
     }
 
@@ -263,13 +260,12 @@ impl SnapshotRequestHandler {
     }
 
     fn handle_snapshot_request(
-        &self,
+        &mut self,
         test_hash_calculation: bool,
         non_snapshot_time_us: u128,
         last_full_snapshot_slot: &mut Option<Slot>,
         snapshot_request: SnapshotRequest,
         accounts_package_type: AccountsPackageType,
-        snapshot_slot_storages: &mut VecDeque<SnapshotStorages>,
     ) -> Result<u64, SnapshotError> {
         debug!(
             "handling snapshot request: {:?}, {:?}",
@@ -379,12 +375,10 @@ impl SnapshotRequestHandler {
                     accounts_hash_for_testing,
                 )
                 .expect("new accounts package for snapshot");
-                snapshot_slot_storages.push_back(snapshot_storages);
+                // Update the option, so the older one is released, causing the release of
+                // its reference counts of the appendvecs
+                let _ret = self.latest_slot_snapshot_storages.insert(snapshot_storages);
 
-                // Remove the older ones, causing them to release the reference counts of the appendvecs
-                while snapshot_slot_storages.len() > 1 {
-                    snapshot_slot_storages.pop_front();
-                }
                 accounts_package
             }
             SnapshotRequestType::EpochAccountsHash => {
@@ -515,17 +509,15 @@ pub struct AbsRequestHandlers {
 impl AbsRequestHandlers {
     // Returns the latest requested snapshot block height, if one exists
     pub fn handle_snapshot_requests(
-        &self,
+        &mut self,
         test_hash_calculation: bool,
         non_snapshot_time_us: u128,
         last_full_snapshot_slot: &mut Option<Slot>,
-        snapshot_slot_storages: &mut VecDeque<SnapshotStorages>,
     ) -> Option<Result<u64, SnapshotError>> {
         self.snapshot_request_handler.handle_snapshot_requests(
             test_hash_calculation,
             non_snapshot_time_us,
             last_full_snapshot_slot,
-            snapshot_slot_storages,
         )
     }
 }
@@ -538,7 +530,7 @@ impl AccountsBackgroundService {
     pub fn new(
         bank_forks: Arc<RwLock<BankForks>>,
         exit: &Arc<AtomicBool>,
-        request_handlers: AbsRequestHandlers,
+        mut request_handlers: AbsRequestHandlers,
         test_hash_calculation: bool,
         mut last_full_snapshot_slot: Option<Slot>,
     ) -> Self {
@@ -548,7 +540,6 @@ impl AccountsBackgroundService {
         let mut removed_slots_count = 0;
         let mut total_remove_slots_time = 0;
         let mut last_expiration_check_time = Instant::now();
-        let mut snapshot_slot_storages: VecDeque<SnapshotStorages> = VecDeque::new();
         let t_background = Builder::new()
             .name("solBgAccounts".to_string())
             .spawn(move || {
@@ -609,7 +600,6 @@ impl AccountsBackgroundService {
                                 test_hash_calculation,
                                 non_snapshot_time,
                                 &mut last_full_snapshot_slot,
-                                &mut snapshot_slot_storages,
                             )
                         })
                         .flatten();
@@ -817,6 +807,7 @@ mod test {
             snapshot_request_sender: snapshot_request_sender.clone(),
             snapshot_request_receiver,
             accounts_package_sender,
+            latest_slot_snapshot_storages: None,
         };
 
         let send_snapshot_request = |snapshot_root_bank, request_type| {