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add uncleaned roots when we shrink away non-zero lamport accounts #2824

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add uncleaned roots when we shrink away non-zero lamport accounts #2824

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29 changes: 29 additions & 0 deletions accounts-db/src/accounts_db.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2038,6 +2038,7 @@ pub struct ShrinkStats {
accounts_loaded: AtomicU64,
purged_zero_lamports: AtomicU64,
accounts_not_found_in_index: AtomicU64,
adding_slots_to_clean: AtomicU64,
}

impl ShrinkStats {
Expand Down Expand Up @@ -2156,6 +2157,11 @@ impl ShrinkStats {
self.accounts_not_found_in_index.swap(0, Ordering::Relaxed),
i64
),
(
"adding_slots_to_clean",
self.adding_slots_to_clean.swap(0, Ordering::Relaxed),
i64
),
);
}
}
Expand Down Expand Up @@ -2384,6 +2390,13 @@ impl ShrinkAncientStats {
.swap(0, Ordering::Relaxed),
i64
),
(
"adding_slots_to_clean",
self.shrink_stats
.adding_slots_to_clean
.swap(0, Ordering::Relaxed),
i64
),
);
}
}
Expand Down Expand Up @@ -3960,6 +3973,7 @@ impl AccountsDb {
let mut alive = 0;
let mut dead = 0;
let mut index = 0;
let mut adding_slots_to_clean = 0;
let mut index_scan_returned_some_count = 0;
let mut index_scan_returned_none_count = 0;
let mut all_are_zero_lamports = true;
Expand Down Expand Up @@ -4006,6 +4020,18 @@ impl AccountsDb {
unrefed_pubkeys.push(pubkey);
result = AccountsIndexScanResult::Unref;
dead += 1;

// If we are marking something dead, and the only remaining alive account is zero lamport, then make that zero lamport slot ready to be cleaned.
// If that slot happens to only contain zero lamport accounts, the whole slot will go away
if slot_list.len() == 1 // should we also check for ref counts here?
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Is it possible that the slot_list contains more than one zero lamport accounts?
Can we relax the requirement for slot_list.len() ==1?

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What about not checking the slot list len, but instead seeing if the latest slot list entry's account info is zero lamports? (Maybe we'd also need to bound the latest entry to be a storage and not a cached entry?)

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I think we should check for ref count. However, we should check after we have unref'd this one. There can be 3 refs, 1 alive that is zero lamport. Each time we unref a pubkey in shrink where the alive one is dead, we should check if refcount has become 1. If so, we know this account can be marked dead and shrunk or entire slot cleaned.

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also, see:
4bb2d91

&& slot_list
.iter()
.all(|(_slot, acct_info)| acct_info.is_zero_lamport())
{
adding_slots_to_clean += 1;
self.accounts_index
.add_uncleaned_roots(slot_list.iter().map(|(slot, _)| *slot));
}
} else {
do_populate_accounts_for_shrink(ref_count, slot_list);
}
Expand Down Expand Up @@ -4036,6 +4062,9 @@ impl AccountsDb {
.fetch_add(index_scan_returned_none_count, Ordering::Relaxed);
stats.alive_accounts.fetch_add(alive, Ordering::Relaxed);
stats.dead_accounts.fetch_add(dead, Ordering::Relaxed);
stats
.adding_slots_to_clean
.fetch_add(adding_slots_to_clean, Ordering::Relaxed);

LoadAccountsIndexForShrink {
alive_accounts,
Expand Down