AcctIdx: metric for active bg threads (#20026)

runtime/src/accounts_index_storage.rs

@@ -109,11 +109,13 @@ impl<T: IndexValue> AccountsIndexStorage<T> {
                 break;
             }
 
+            storage.stats.active_threads.fetch_add(1, Ordering::Relaxed);
             for bucket in &in_mem {
                 bucket.flush();
             }
 
             storage.stats.report_stats();
+            storage.stats.active_threads.fetch_sub(1, Ordering::Relaxed);
         }
     }
 }

runtime/src/bucket_map_holder_stats.rs

@@ -19,6 +19,7 @@ pub struct BucketMapHolderStats {
     pub inserts: AtomicU64,
     pub count_in_mem: AtomicU64,
     pub per_bucket_count: Vec<AtomicU64>,
+    pub active_threads: AtomicU64,
     pub get_range_us: AtomicU64,
     last_time: AtomicInterval,
 }
@@ -125,6 +126,11 @@ impl BucketMapHolderStats {
             ),
             ("inserts", self.inserts.swap(0, Ordering::Relaxed), i64),
             ("deletes", self.deletes.swap(0, Ordering::Relaxed), i64),
+            (
+                "active_threads",
+                self.active_threads.load(Ordering::Relaxed),
+                i64
+            ),
             ("items", self.items.swap(0, Ordering::Relaxed), i64),
             ("keys", self.keys.swap(0, Ordering::Relaxed), i64),
         );