AcctIdx: upsert avoids unnecessary allocation (solana-labs#21488)

runtime/src/accounts_index.rs

@@ -1694,6 +1694,9 @@ impl<T: IndexValue> AccountsIndex<T> {
         reclaims: &mut SlotList<T>,
         previous_slot_entry_was_cached: bool,
     ) {
+        // vast majority of updates are to item already in accounts index, so store as raw to avoid unnecessary allocations
+        let store_raw = true;
+
         // We don't atomically update both primary index and secondary index together.
         // This certainly creates a small time window with inconsistent state across the two indexes.
         // However, this is acceptable because:
@@ -1706,7 +1709,7 @@ impl<T: IndexValue> AccountsIndex<T> {
         //  So, what the accounts_index sees alone is sufficient as a source of truth for other non-scan
         //  account operations.
         let new_item =
-            PreAllocatedAccountMapEntry::new(slot, account_info, &self.storage.storage, false);
+            PreAllocatedAccountMapEntry::new(slot, account_info, &self.storage.storage, store_raw);
         let map = &self.account_maps[self.bin_calculator.bin_from_pubkey(pubkey)];
 
         {
@@ -2883,36 +2886,69 @@ pub mod tests {
         assert_eq!(num, 1);
     }
 
+    fn get_pre_allocated<T: IndexValue>(
+        slot: Slot,
+        account_info: T,
+        storage: &Arc<BucketMapHolder<T>>,
+        store_raw: bool,
+        to_raw_first: bool,
+    ) -> PreAllocatedAccountMapEntry<T> {
+        let entry = PreAllocatedAccountMapEntry::new(slot, account_info, storage, store_raw);
+
+        if to_raw_first {
+            // convert to raw
+            let (slot2, account_info2) = entry.into();
+            // recreate using extracted raw
+            PreAllocatedAccountMapEntry::new(slot2, account_info2, storage, store_raw)
+        } else {
+            entry
+        }
+    }
+
     #[test]
     fn test_new_entry() {
-        let slot = 0;
-        // account_info type that IS cached
-        let account_info = AccountInfoTest::default();
-        let index = AccountsIndex::default_for_tests();
-
-        let new_entry: AccountMapEntry<_> =
-            PreAllocatedAccountMapEntry::new(slot, account_info, &index.storage.storage, false)
+        for store_raw in [false, true] {
+            for to_raw_first in [false, true] {
+                let slot = 0;
+                // account_info type that IS cached
+                let account_info = AccountInfoTest::default();
+                let index = AccountsIndex::default_for_tests();
+
+                let new_entry = get_pre_allocated(
+                    slot,
+                    account_info,
+                    &index.storage.storage,
+                    store_raw,
+                    to_raw_first,
+                )
                 .into_account_map_entry(&index.storage.storage);
-        assert_eq!(new_entry.ref_count.load(Ordering::Relaxed), 0);
-        assert_eq!(new_entry.slot_list.read().unwrap().capacity(), 1);
-        assert_eq!(
-            new_entry.slot_list.read().unwrap().to_vec(),
-            vec![(slot, account_info)]
-        );
+                assert_eq!(new_entry.ref_count.load(Ordering::Relaxed), 0);
+                assert_eq!(new_entry.slot_list.read().unwrap().capacity(), 1);
+                assert_eq!(
+                    new_entry.slot_list.read().unwrap().to_vec(),
+                    vec![(slot, account_info)]
+                );
 
-        // account_info type that is NOT cached
-        let account_info = true;
-        let index = AccountsIndex::default_for_tests();
+                // account_info type that is NOT cached
+                let account_info = true;
+                let index = AccountsIndex::default_for_tests();
 
-        let new_entry: AccountMapEntry<_> =
-            PreAllocatedAccountMapEntry::new(slot, account_info, &index.storage.storage, false)
+                let new_entry = get_pre_allocated(
+                    slot,
+                    account_info,
+                    &index.storage.storage,
+                    store_raw,
+                    to_raw_first,
+                )
                 .into_account_map_entry(&index.storage.storage);
-        assert_eq!(new_entry.ref_count.load(Ordering::Relaxed), 1);
-        assert_eq!(new_entry.slot_list.read().unwrap().capacity(), 1);
-        assert_eq!(
-            new_entry.slot_list.read().unwrap().to_vec(),
-            vec![(slot, account_info)]
-        );
+                assert_eq!(new_entry.ref_count.load(Ordering::Relaxed), 1);
+                assert_eq!(new_entry.slot_list.read().unwrap().capacity(), 1);
+                assert_eq!(
+                    new_entry.slot_list.read().unwrap().to_vec(),
+                    vec![(slot, account_info)]
+                );
+            }
+        }
     }
 
     #[test]