From 84f74807d45170edea90a7ba39d4c46f087b5f5a Mon Sep 17 00:00:00 2001
From: Sagar Dhawan <sagar@solana.com>
Date: Mon, 23 Sep 2019 19:40:03 -0700
Subject: [PATCH] Skip considering banks older than the latest vote slot
 (#6037)

automerge
---
 core/src/consensus.rs    | 14 ++++++++++----
 core/src/replay_stage.rs |  5 -----
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/core/src/consensus.rs b/core/src/consensus.rs
index 83bb2fe504..786efde574 100644
--- a/core/src/consensus.rs
+++ b/core/src/consensus.rs
@@ -253,10 +253,10 @@ impl Tower {
         sum
     }
 
-    // a slot is not recent if its older than the oldest lockout we have
-    pub fn is_recent(&self, slot: u64) -> bool {
-        if let Some(oldest_vote) = self.lockouts.votes.front() {
-            if slot < oldest_vote.slot {
+    // a slot is not recent if it's older than the newest vote we have
+    fn is_recent(&self, slot: u64) -> bool {
+        if let Some(last_vote) = self.lockouts.votes.back() {
+            if slot <= last_vote.slot {
                 return false;
             }
         }
@@ -275,6 +275,11 @@ impl Tower {
     pub fn is_locked_out(&self, slot: u64, ancestors: &HashMap<u64, HashSet<u64>>) -> bool {
         assert!(ancestors.contains_key(&slot));
 
+        if !self.is_recent(slot) {
+            trace!("slot is not recent: {}", slot);
+            return true;
+        }
+
         let mut lockouts = self.lockouts.clone();
         lockouts.process_slot_vote_unchecked(slot);
         for vote in &lockouts.votes {
@@ -610,6 +615,7 @@ mod test {
         }
         assert!(!tower.is_recent(0));
         assert!(!tower.is_recent(32));
+        assert!(!tower.is_recent(63));
         assert!(tower.is_recent(65));
     }
 
diff --git a/core/src/replay_stage.rs b/core/src/replay_stage.rs
index 0cc50bd564..97bc20a170 100644
--- a/core/src/replay_stage.rs
+++ b/core/src/replay_stage.rs
@@ -574,11 +574,6 @@ impl ReplayStage {
                 trace!("bank is votable: {} {}", b.slot(), is_votable);
                 is_votable
             })
-            .filter(|b| {
-                let is_recent = tower.is_recent(b.slot());
-                trace!("tower is recent: {} {}", b.slot(), is_recent);
-                is_recent
-            })
             .filter(|b| {
                 let has_voted = tower.has_voted(b.slot());
                 trace!("bank has_voted: {} {}", b.slot(), has_voted);