comment loop in function (#27454)

runtime/src/accounts_db.rs

@@ -7660,6 +7660,7 @@ impl AccountsDb {
     ) {
         let mut measure = Measure::start("clean_stored_dead_slots-ms");
         let mut stores: Vec<Arc<AccountStorageEntry>> = vec![];
+        // get all stores in a vec so we can iterate in parallel
         for slot in dead_slots.iter() {
             if let Some(slot_storage) = self.storage.get_slot_stores(*slot) {
                 for store in slot_storage.read().unwrap().values() {
@@ -7667,6 +7668,7 @@ impl AccountsDb {
                 }
             }
         }
+        // get all pubkeys in all dead slots
         let purged_slot_pubkeys: HashSet<(Slot, Pubkey)> = {
             self.thread_pool_clean.install(|| {
                 stores