Make run_pending_tasks to evict more entries from the cache at once

- Disable the eviction batch size when the eviction listener is not set to the cache.
  - So single `run_pending_tasks` call should remove all entries that can be evicted
    from the cache.
- Add a hard-coded maintenance task timeout duration.
  - When the eviction listener is set, `run_pending_tasks` should stop (return) after
    the maintenance task timeout is elapsed.
  - This is a safe-guard to prevent the maintenance task from running long time when
    the user wrote a slow eviction listener.
  - In older versions, the batch size was used to limit the time spent on the
    maintenance task.
  - Not that `run_pending_tasks` checks the timeout only after processing a batch
    of entries, so `run_pending_tasks` can run longer than the timeout duration.
- Reduce the size of the read op and write op channels.

src/common/concurrent/constants.rs

@@ -1,11 +1,19 @@
 pub(crate) const MAX_SYNC_REPEATS: usize = 4;
 pub(crate) const PERIODICAL_SYNC_INITIAL_DELAY_MILLIS: u64 = 300;
 
-pub(crate) const READ_LOG_FLUSH_POINT: usize = 512;
-pub(crate) const READ_LOG_SIZE: usize = READ_LOG_FLUSH_POINT * (MAX_SYNC_REPEATS + 2);
+pub(crate) const READ_LOG_FLUSH_POINT: usize = 64;
+pub(crate) const READ_LOG_SIZE: usize = READ_LOG_FLUSH_POINT * (MAX_SYNC_REPEATS + 2); // 384
 
-pub(crate) const WRITE_LOG_FLUSH_POINT: usize = 512;
-pub(crate) const WRITE_LOG_SIZE: usize = WRITE_LOG_FLUSH_POINT * (MAX_SYNC_REPEATS + 2);
+pub(crate) const WRITE_LOG_FLUSH_POINT: usize = 64;
+pub(crate) const WRITE_LOG_SIZE: usize = WRITE_LOG_FLUSH_POINT * (MAX_SYNC_REPEATS + 2); // 384
+
+// TODO: Calculate the batch size based on the number of entries in the cache (or an
+// estimated number of entries to evict)
+pub(crate) const EVICTION_BATCH_SIZE: usize = WRITE_LOG_SIZE;
+pub(crate) const INVALIDATION_BATCH_SIZE: usize = WRITE_LOG_SIZE;
+
+/// The default timeout duration for the `run_pending_tasks` method.
+pub(crate) const DEFAULT_RUN_PENDING_TASKS_TIMEOUT_MILLIS: u64 = 100;
 
 #[cfg(feature = "sync")]
 pub(crate) const WRITE_RETRY_INTERVAL_MICROS: u64 = 50;

src/common/concurrent/housekeeper.rs

@@ -36,11 +36,11 @@ impl Default for Housekeeper {
 
 impl Housekeeper {
     pub(crate) fn should_apply_reads(&self, ch_len: usize, now: Instant) -> bool {
-        self.should_apply(ch_len, READ_LOG_FLUSH_POINT / 8, now)
+        self.should_apply(ch_len, READ_LOG_FLUSH_POINT, now)
     }
 
     pub(crate) fn should_apply_writes(&self, ch_len: usize, now: Instant) -> bool {
-        self.should_apply(ch_len, WRITE_LOG_FLUSH_POINT / 8, now)
+        self.should_apply(ch_len, WRITE_LOG_FLUSH_POINT, now)
     }
 
     #[inline]