Re-enable page bool with default size of 128 pages (#2769)

Author: joshua-spacetime

crates/table/src/page_pool.rs

@@ -32,16 +32,15 @@ impl PagePool {
     /// if no size is provided, a default of 1 page is used.
     pub fn new(max_size: Option<usize>) -> Self {
         const PAGE_SIZE: usize = size_of::<Page>();
-        // TODO(centril): This effectively disables the page pool.
-        // Currently, we have a test `test_index_scans`.
+        // TODO(centril): Currently, we have a test `test_index_scans`.
         // The test sets up a `Location` table, like in BitCraft, with a `chunk` field,
         // and populates it with 1000 different chunks with 1200 rows each.
         // Then it asserts that the cold latency of an index scan on `chunk` takes < 1 ms.
         // However, for reasons currently unknown to us,
         // a large page pool, with capacity `1 << 26` bytes, on i7-7700K, 64GB RAM,
         // will turn the latency into 30-40 ms.
-        // As a precaution, we disable the page pool by default.
-        const DEFAULT_MAX_SIZE: usize = PAGE_SIZE; // 1 page
+        // As a precaution, we use a smaller page pool by default.
+        const DEFAULT_MAX_SIZE: usize = 128 * PAGE_SIZE; // 128 pages
 
         let queue_size = max_size.unwrap_or(DEFAULT_MAX_SIZE) / PAGE_SIZE;
         let inner = Arc::new(PagePoolInner::new(queue_size));