chore(hash*): minor performance tuning

Author: wvwwvwwv

README.md

@@ -36,7 +36,7 @@ Resizing of a [`HashMap`](#hashmap) is entirely non-blocking and lock-free; resi
 
 ### Examples
 
-If the key is unique, an entry can be inserted. The inserted entry can be updated, read, and removed synchronously or asynchronously.
+Inserted entries can be updated, read, and removed synchronously or asynchronously.
 
 ```rust
 use scc::HashMap;

src/hash_table.rs

@@ -1323,6 +1323,29 @@ where
             return;
         }
 
+        if self
+            .minimum_capacity_var()
+            .fetch_update(AcqRel, Acquire, |lock_state| {
+                if lock_state >= RESIZING {
+                    None
+                } else {
+                    Some(lock_state + RESIZING)
+                }
+            })
+            .is_err()
+        {
+            // The bucket array is being replaced with a new one.
+            return;
+        }
+        let _lock_guard = ExitGuard::new((), |()| {
+            self.minimum_capacity_var().fetch_sub(RESIZING, Release);
+        });
+
+        if self.bucket_array_var().load(Acquire, guard) != current_array_ptr {
+            // Resized in the meantime.
+            return;
+        }
+
         let minimum_capacity = self.minimum_capacity();
         let capacity = current_array.num_slots();
         let estimated_num_entries = Self::sample(current_array, sampling_index);
@@ -1362,28 +1385,6 @@ where
             return;
         }
 
-        if self
-            .minimum_capacity_var()
-            .fetch_update(AcqRel, Acquire, |lock_state| {
-                if lock_state >= RESIZING {
-                    None
-                } else {
-                    Some(lock_state + RESIZING)
-                }
-            })
-            .is_err()
-        {
-            // The bucket array is being replaced with a new one.
-            return;
-        }
-        let _lock_guard = ExitGuard::new((), |()| {
-            self.minimum_capacity_var().fetch_sub(RESIZING, Release);
-        });
-
-        if self.bucket_array_var().load(Acquire, guard) != current_array_ptr {
-            return;
-        }
-
         if try_drop_table {
             // Try to drop the hash table with all the buckets locked.
             let mut writer_guard = ExitGuard::new((0, false), |(len, success): (usize, bool)| {