Rust container growth rate: 2x to 1.5x

gistfile1.diff

diff --git a/src/libcore/at_vec.rs b/src/libcore/at_vec.rs
index d894817..bc3f547 100644
--- a/src/libcore/at_vec.rs
+++ b/src/libcore/at_vec.rs
@@ -269,7 +269,7 @@ pub mod raw {
      * * n - The number of elements to reserve space for
      */
     pub unsafe fn reserve_at_least<T>(v: &mut @[const T], n: uint) {
-        reserve(v, uint::next_power_of_two(n));
+        reserve(v, n + (n>>1));
     }
 
 }
diff --git a/src/libcore/hashmap.rs b/src/libcore/hashmap.rs
index 43ec629..65203a3 100644
--- a/src/libcore/hashmap.rs
+++ b/src/libcore/hashmap.rs
@@ -365,7 +365,7 @@ pub mod linear {
         fn reserve_at_least(&mut self, n: uint) {
             if n > self.buckets.len() {
                 let buckets = n * 4 / 3 + 1;
-                self.resize(uint::next_power_of_two(buckets));
+                self.resize(buckets + (buckets>>1));
             }
         }
 
diff --git a/src/libcore/str.rs b/src/libcore/str.rs
index 19453c5..b7c953d 100644
--- a/src/libcore/str.rs
+++ b/src/libcore/str.rs
@@ -1995,7 +1995,7 @@ pub fn reserve(s: &mut ~str, n: uint) {
  * * n - The number of bytes to reserve space for
  */
 pub fn reserve_at_least(s: &mut ~str, n: uint) {
-    reserve(s, uint::next_power_of_two(n + 1u) - 1u)
+    reserve(s, n + (n>>1) + 1);
 }
 
 /**
diff --git a/src/libcore/vec.rs b/src/libcore/vec.rs
index ab5f04a..74477b7 100644
--- a/src/libcore/vec.rs
+++ b/src/libcore/vec.rs
@@ -94,7 +94,7 @@ pub fn reserve<T>(v: &mut ~[T], n: uint) {
  * * n - The number of elements to reserve space for
  */
 pub fn reserve_at_least<T>(v: &mut ~[T], n: uint) {
-    reserve(v, uint::next_power_of_two(n));
+    reserve(v, n + (n>>1));
 }
 
 /// Returns the number of elements the vector can hold without reallocating
diff --git a/src/libstd/oldmap.rs b/src/libstd/oldmap.rs
index faa26e2..e8f39b2 100644
--- a/src/libstd/oldmap.rs
+++ b/src/libstd/oldmap.rs
@@ -122,7 +122,7 @@ pub mod chained {
 
         fn rehash() {
             let n_old_chains = self.chains.len();
-            let n_new_chains: uint = uint::next_power_of_two(n_old_chains+1u);
+            let n_new_chains = n_old_chains + (n_old_chains>>1) + 1;
             let mut new_chains = chains(n_new_chains);
             for self.each_entry |entry| {
                 let idx = entry.hash % n_new_chains;