From fa9205e75fdb7279ee516f93ccd398d6ff7e9197 Mon Sep 17 00:00:00 2001
From: "Jeff Washington (jwash)" <jeff.washington@anza.xyz>
Date: Tue, 30 Jul 2024 09:57:22 -0500
Subject: [PATCH] clean doesn't try to remove older entries on 1 elem slot list
 (#2308)

* clean doesn't try to remove older entries on 1 elem slot list

* move useless
---
 accounts-db/src/accounts_db.rs    | 26 ++++++++++++++++++++++++--
 accounts-db/src/accounts_index.rs |  7 +++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/accounts-db/src/accounts_db.rs b/accounts-db/src/accounts_db.rs
index c06fb5408466be..94834338c18ee0 100644
--- a/accounts-db/src/accounts_db.rs
+++ b/accounts-db/src/accounts_db.rs
@@ -1937,6 +1937,7 @@ struct CleanAccountsStats {
     remove_dead_accounts_remove_us: AtomicU64,
     remove_dead_accounts_shrink_us: AtomicU64,
     clean_stored_dead_slots_us: AtomicU64,
+    uncleaned_roots_slot_list_1: AtomicU64,
 }
 
 impl CleanAccountsStats {
@@ -3282,8 +3283,15 @@ impl AccountsDb {
                                                 {
                                                     assert!(slot <= &max_clean_root_inclusive);
                                                 }
-                                                purges_old_accounts.push(*candidate);
-                                                useless = false;
+                                                if slot_list.len() > 1 {
+                                                    // no need to purge old accounts if there is only 1 slot in the slot list
+                                                    purges_old_accounts.push(*candidate);
+                                                    useless = false;
+                                                } else {
+                                                    self.clean_accounts_stats
+                                                        .uncleaned_roots_slot_list_1
+                                                        .fetch_add(1, Ordering::Relaxed);
+                                                }
                                             }
                                         }
                                         None => {
@@ -3497,6 +3505,13 @@ impl AccountsDb {
             ),
             ("scan_missing", missing_accum.load(Ordering::Relaxed), i64),
             ("uncleaned_roots_len", uncleaned_roots.len(), i64),
+            (
+                "uncleaned_roots_slot_list_1",
+                self.clean_accounts_stats
+                    .uncleaned_roots_slot_list_1
+                    .swap(0, Ordering::Relaxed),
+                i64
+            ),
             (
                 "clean_old_root_us",
                 self.clean_accounts_stats
@@ -3544,6 +3559,13 @@ impl AccountsDb {
                 self.accounts_index.roots_added.swap(0, Ordering::Relaxed),
                 i64
             ),
+            (
+                "purge_older_root_entries_one_slot_list",
+                self.accounts_index
+                    .purge_older_root_entries_one_slot_list
+                    .swap(0, Ordering::Relaxed),
+                i64
+            ),
             (
                 "roots_removed",
                 self.accounts_index.roots_removed.swap(0, Ordering::Relaxed),
diff --git a/accounts-db/src/accounts_index.rs b/accounts-db/src/accounts_index.rs
index ee0392ce856873..dc10df29d67e35 100644
--- a/accounts-db/src/accounts_index.rs
+++ b/accounts-db/src/accounts_index.rs
@@ -666,6 +666,8 @@ pub struct AccountsIndex<T: IndexValue, U: DiskIndexValue + From<T> + Into<T>> {
     /// when a scan's accumulated data exceeds this limit, abort the scan
     pub scan_results_limit_bytes: Option<usize>,
 
+    pub purge_older_root_entries_one_slot_list: AtomicUsize,
+
     /// # roots added since last check
     pub roots_added: AtomicUsize,
     /// # roots removed since last check
@@ -690,6 +692,7 @@ impl<T: IndexValue, U: DiskIndexValue + From<T> + Into<T>> AccountsIndex<T, U> {
             .and_then(|config| config.scan_results_limit_bytes);
         let (account_maps, bin_calculator, storage) = Self::allocate_accounts_index(config, exit);
         Self {
+            purge_older_root_entries_one_slot_list: AtomicUsize::default(),
             account_maps,
             bin_calculator,
             program_id_index: SecondaryIndex::<RwLockSecondaryIndexEntry>::new(
@@ -1817,6 +1820,10 @@ impl<T: IndexValue, U: DiskIndexValue + From<T> + Into<T>> AccountsIndex<T, U> {
         reclaims: &mut SlotList<T>,
         max_clean_root_inclusive: Option<Slot>,
     ) {
+        if slot_list.len() <= 1 {
+            self.purge_older_root_entries_one_slot_list
+                .fetch_add(1, Ordering::Relaxed);
+        }
         let newest_root_in_slot_list;
         let max_clean_root_inclusive = {
             let roots_tracker = &self.roots_tracker.read().unwrap();