solana_runtime/
root_bank_cache.rs

1//! A wrapper around a root `Bank` that only loads from bank forks if the root has been updated.
2//! This can be useful to avoid read-locking the bank forks until the root has been updated.
3//!
4
5use {
6    crate::{
7        bank::Bank,
8        bank_forks::{BankForks, ReadOnlyAtomicSlot},
9    },
10    std::sync::{Arc, RwLock, Weak},
11};
12
13/// Cached root bank that only loads from bank forks if the root has been updated.
14pub struct RootBankCache {
15    bank_forks: Arc<RwLock<BankForks>>,
16    cached_root_bank: Weak<Bank>,
17    root_slot: ReadOnlyAtomicSlot,
18}
19
20impl RootBankCache {
21    pub fn new(bank_forks: Arc<RwLock<BankForks>>) -> Self {
22        let (cached_root_bank, root_slot) = {
23            let lock = bank_forks.read().unwrap();
24            (Arc::downgrade(&lock.root_bank()), lock.get_atomic_root())
25        };
26        Self {
27            bank_forks,
28            cached_root_bank,
29            root_slot,
30        }
31    }
32
33    pub fn root_bank(&mut self) -> Arc<Bank> {
34        match self.cached_root_bank.upgrade() {
35            Some(cached_root_bank) if cached_root_bank.slot() == self.root_slot.get() => {
36                cached_root_bank
37            }
38            _ => {
39                let root_bank = self.bank_forks.read().unwrap().root_bank();
40                self.cached_root_bank = Arc::downgrade(&root_bank);
41                root_bank
42            }
43        }
44    }
45}
46
47#[cfg(test)]
48mod tests {
49    use {
50        super::*,
51        crate::{
52            accounts_background_service::AbsRequestSender,
53            bank_forks::BankForks,
54            genesis_utils::{create_genesis_config, GenesisConfigInfo},
55        },
56        solana_sdk::pubkey::Pubkey,
57    };
58
59    #[test]
60    fn test_root_bank_cache() {
61        let GenesisConfigInfo { genesis_config, .. } = create_genesis_config(10_000);
62        let bank = Bank::new_for_tests(&genesis_config);
63        let bank_forks = BankForks::new_rw_arc(bank);
64
65        let mut root_bank_cache = RootBankCache::new(bank_forks.clone());
66
67        let bank = bank_forks.read().unwrap().root_bank();
68        assert_eq!(bank, root_bank_cache.root_bank());
69
70        {
71            let child_bank = Bank::new_from_parent(bank.clone(), &Pubkey::default(), 1);
72            bank_forks.write().unwrap().insert(child_bank);
73
74            // cached slot is still 0 since we have not set root
75            let cached_root_bank = root_bank_cache.cached_root_bank.upgrade().unwrap();
76            assert_eq!(bank.slot(), cached_root_bank.slot());
77        }
78        {
79            bank_forks
80                .write()
81                .unwrap()
82                .set_root(1, &AbsRequestSender::default(), None)
83                .unwrap();
84            let bank = bank_forks.read().unwrap().root_bank();
85
86            // cached slot and bank are not updated until we call `root_bank()`
87            let cached_root_bank = root_bank_cache.cached_root_bank.upgrade().unwrap();
88            assert!(bank.slot() != cached_root_bank.slot());
89            assert!(bank != cached_root_bank);
90            assert_eq!(bank, root_bank_cache.root_bank());
91
92            // cached slot and bank are updated
93            let cached_root_bank = root_bank_cache.cached_root_bank.upgrade().unwrap();
94            assert_eq!(bank.slot(), cached_root_bank.slot());
95            assert_eq!(bank, cached_root_bank);
96            assert_eq!(bank, root_bank_cache.root_bank());
97        }
98    }
99}
solana_runtime/root_bank_cache.rs

solana_runtime/
root_bank_cache.rs
