Add stats for readonly cache evicts (#26938)

* add stats for readonly cache evicts

* bump up account cache to 400M

* aggregate num_evicts in the loop

runtime/src/accounts_db.rs

@@ -1902,7 +1902,7 @@ impl AccountsDb {
         num_hash_scan_passes: Option<usize>,
     ) -> Self {
         let num_threads = get_thread_count();
-        const MAX_READ_ONLY_CACHE_DATA_SIZE: usize = 200_000_000;
+        const MAX_READ_ONLY_CACHE_DATA_SIZE: usize = 400_000_000; // 400M bytes
 
         let mut temp_accounts_hash_cache_path = None;
         let accounts_hash_cache_path = accounts_hash_cache_path.unwrap_or_else(|| {
@@ -7637,7 +7637,7 @@ impl AccountsDb {
 
     fn report_store_timings(&self) {
         if self.stats.last_store_report.should_update(1000) {
-            let (read_only_cache_hits, read_only_cache_misses) =
+            let (read_only_cache_hits, read_only_cache_misses, read_only_cache_evicts) =
                 self.read_only_accounts_cache.get_and_reset_stats();
             datapoint_info!(
                 "accounts_db_store_timings",
@@ -7704,6 +7704,11 @@ impl AccountsDb {
                     read_only_cache_misses,
                     i64
                 ),
+                (
+                    "read_only_accounts_cache_evicts",
+                    read_only_cache_evicts,
+                    i64
+                ),
                 (
                     "calc_stored_meta_us",
                     self.stats.calc_stored_meta.swap(0, Ordering::Relaxed),

runtime/src/read_only_accounts_cache.rs

@@ -38,6 +38,7 @@ pub(crate) struct ReadOnlyAccountsCache {
     data_size: AtomicUsize,
     hits: AtomicU64,
     misses: AtomicU64,
+    evicts: AtomicU64,
 }
 
 impl ReadOnlyAccountsCache {
@@ -49,6 +50,7 @@ impl ReadOnlyAccountsCache {
             data_size: AtomicUsize::default(),
             hits: AtomicU64::default(),
             misses: AtomicU64::default(),
+            evicts: AtomicU64::default(),
         }
     }
 
@@ -107,13 +109,16 @@ impl ReadOnlyAccountsCache {
             }
         };
         // Evict entries from the front of the queue.
+        let mut num_evicts = 0;
         while self.data_size.load(Ordering::Relaxed) > self.max_data_size {
             let (pubkey, slot) = match self.queue.lock().unwrap().get_first() {
                 None => break,
                 Some(key) => *key,
             };
+            num_evicts += 1;
             self.remove(pubkey, slot);
         }
+        self.evicts.fetch_add(num_evicts, Ordering::Relaxed);
     }
 
     pub(crate) fn remove(&self, pubkey: Pubkey, slot: Slot) -> Option<AccountSharedData> {
@@ -135,10 +140,12 @@ impl ReadOnlyAccountsCache {
         self.data_size.load(Ordering::Relaxed)
     }
 
-    pub(crate) fn get_and_reset_stats(&self) -> (u64, u64) {
+    pub(crate) fn get_and_reset_stats(&self) -> (u64, u64, u64) {
         let hits = self.hits.swap(0, Ordering::Relaxed);
         let misses = self.misses.swap(0, Ordering::Relaxed);
-        (hits, misses)
+        let evicts = self.evicts.swap(0, Ordering::Relaxed);
+
+        (hits, misses, evicts)
     }
 }