From e9ab2142371a98b207819007e5bdc0663c5a164e Mon Sep 17 00:00:00 2001
From: "Jeff Washington (jwash)"
 <75863576+jeffwashington@users.noreply.github.com>
Date: Thu, 28 Oct 2021 10:26:30 -0500
Subject: [PATCH] filler accts: only add filler accts to slots in the current
 epoch (#21024)

---
 runtime/src/accounts_db.rs | 21 +++++++++++++++++++--
 runtime/src/bank.rs        |  6 ++++--
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/runtime/src/accounts_db.rs b/runtime/src/accounts_db.rs
index 82dffb269f..8f27563f37 100644
--- a/runtime/src/accounts_db.rs
+++ b/runtime/src/accounts_db.rs
@@ -52,7 +52,7 @@ use solana_measure::measure::Measure;
 use solana_rayon_threadlimit::get_thread_count;
 use solana_sdk::{
     account::{AccountSharedData, ReadableAccount},
-    clock::{BankId, Epoch, Slot},
+    clock::{BankId, Epoch, Slot, SlotCount},
     epoch_schedule::EpochSchedule,
     genesis_config::ClusterType,
     hash::{Hash, Hasher},
@@ -6761,6 +6761,14 @@ impl AccountsDb {
         Self::is_filler_account_helper(pubkey, self.filler_account_suffix.as_ref())
     }
 
+    /// retain slots in 'roots' that are > (max(roots) - slots_per_epoch)
+    fn retain_roots_within_one_epoch_range(roots: &mut Vec<Slot>, slots_per_epoch: SlotCount) {
+        if let Some(max) = roots.iter().max() {
+            let min = max - slots_per_epoch;
+            roots.retain(|slot| slot > &min);
+        }
+    }
+
     /// filler accounts are space-holding accounts which are ignored by hash calculations and rent.
     /// They are designed to allow a validator to run against a network successfully while simulating having many more accounts present.
     /// All filler accounts share a common pubkey suffix. The suffix is randomly generated per validator on startup.
@@ -6775,7 +6783,8 @@ impl AccountsDb {
         info!("adding {} filler accounts", self.filler_account_count);
         // break this up to force the accounts out of memory after each pass
         let passes = 100;
-        let roots = self.storage.all_slots();
+        let mut roots = self.storage.all_slots();
+        Self::retain_roots_within_one_epoch_range(&mut roots, epoch_schedule.slots_per_epoch);
         let root_count = roots.len();
         let per_pass = std::cmp::max(1, root_count / passes);
         let overall_index = AtomicUsize::new(0);
@@ -7374,6 +7383,14 @@ pub mod tests {
         }
     }
 
+    #[test]
+    fn test_retain_roots_within_one_epoch_range() {
+        let mut roots = vec![0, 1, 2];
+        let slots_per_epoch = 2;
+        AccountsDb::retain_roots_within_one_epoch_range(&mut roots, slots_per_epoch);
+        assert_eq!(&vec![1, 2], &roots);
+    }
+
     #[test]
     #[should_panic(
         expected = "bin_range.start < bins && bin_range.end <= bins &&\\n    bin_range.start < bin_range.end"
diff --git a/runtime/src/bank.rs b/runtime/src/bank.rs
index 928da98ebc..883ee689f1 100644
--- a/runtime/src/bank.rs
+++ b/runtime/src/bank.rs
@@ -4546,6 +4546,8 @@ impl Bank {
         Self::get_partitions(self.slot(), self.parent_slot(), slot_count_in_two_day)
     }
 
+    /// used only by filler accounts in debug path
+    /// previous means slot - 1, not parent
     pub fn variable_cycle_partition_from_previous_slot(
         epoch_schedule: &EpochSchedule,
         slot: Slot,
@@ -4630,7 +4632,7 @@ impl Bank {
         )
     }
 
-    pub fn get_partition_from_slot_indexes(
+    fn get_partition_from_slot_indexes(
         cycle_params: RentCollectionCycleParams,
         start_slot_index: SlotIndex,
         end_slot_index: SlotIndex,
@@ -4705,7 +4707,7 @@ impl Bank {
         self.do_partition_from_slot_indexes(start_slot_index, end_slot_index, epoch, true)
     }
 
-    pub fn rent_single_epoch_collection_cycle_params(
+    fn rent_single_epoch_collection_cycle_params(
         epoch: Epoch,
         slot_count_per_epoch: SlotCount,
     ) -> RentCollectionCycleParams {