Rehabilitate quadratic pool

jetty-core/jetty-io/src/main/java/org/eclipse/jetty/io/ArrayByteBufferPool.java

@@ -37,6 +37,7 @@
 import org.eclipse.jetty.util.BufferUtil;
 import org.eclipse.jetty.util.ConcurrentPool;
 import org.eclipse.jetty.util.Pool;
+import org.eclipse.jetty.util.TypeUtil;
 import org.eclipse.jetty.util.annotation.ManagedAttribute;
 import org.eclipse.jetty.util.annotation.ManagedObject;
 import org.eclipse.jetty.util.annotation.ManagedOperation;
@@ -723,15 +724,12 @@ protected void acquire()
      * A variant of the {@link ArrayByteBufferPool} that
      * uses buckets of buffers that increase in size by a power of
      * 2 (e.g. 1k, 2k, 4k, 8k, etc.).
-     * @deprecated Usage of {@code Quadratic} is often wasteful of additional space and can increase contention on
-     * the larger buffers.
      */
-    @Deprecated(forRemoval = true, since = "12.1.0")
     public static class Quadratic extends ArrayByteBufferPool
     {
         public Quadratic()
         {
-            this(0, -1, Integer.MAX_VALUE);
+            this(4096, 65536, Integer.MAX_VALUE);
         }
 
         public Quadratic(int minCapacity, int maxCapacity, int maxBucketSize)
@@ -742,13 +740,13 @@ public Quadratic(int minCapacity, int maxCapacity, int maxBucketSize)
         public Quadratic(int minCapacity, int maxCapacity, int maxBucketSize, long maxHeapMemory, long maxDirectMemory)
         {
             super(minCapacity,
-                -1,
+                minCapacity <= 0 ? 1 : minCapacity,
                 maxCapacity,
                 maxBucketSize,
                 maxHeapMemory,
                 maxDirectMemory,
-                c -> 32 - Integer.numberOfLeadingZeros(c - 1),
-                i -> 1 << i
+                c -> 32 - Integer.numberOfLeadingZeros(c - 1) - Integer.numberOfTrailingZeros(Integer.highestOneBit(TypeUtil.ceilToNextPowerOfTwo(minCapacity))),
+                i -> 1 << i + Integer.numberOfTrailingZeros(Integer.highestOneBit(TypeUtil.ceilToNextPowerOfTwo(minCapacity)))
             );
         }
     }

jetty-core/jetty-io/src/test/java/org/eclipse/jetty/io/ArrayByteBufferPoolTest.java

@@ -391,44 +391,37 @@ public void testAcquireRelease()
     }
 
     @Test
-    @Deprecated(forRemoval = true)
-    public void testQuadraticPool()
+    public void testQuadraticPoolBucketSizes()
     {
-        ArrayByteBufferPool pool = new ArrayByteBufferPool.Quadratic();
-
-        RetainableByteBuffer retain5 = pool.acquire(5, false);
-        retain5.release();
-        RetainableByteBuffer retain6 = pool.acquire(6, false);
-        assertThat(retain6, not(sameInstance(retain5)));
-        assertThat(retain6.getByteBuffer(), sameInstance(retain5.getByteBuffer()));
-        retain6.release();
-        RetainableByteBuffer retain9 = pool.acquire(9, false);
-        assertThat(retain9, not(sameInstance(retain5)));
-        retain9.release();
-
-        assertThat(pool.acquire(1, false).capacity(), is(1));
-        assertThat(pool.acquire(2, false).capacity(), is(2));
-        RetainableByteBuffer b3 = pool.acquire(3, false);
-        assertThat(b3.capacity(), is(4));
-        RetainableByteBuffer b4 = pool.acquire(4, false);
-        assertThat(b4.capacity(), is(4));
-
-        int capacity = 4;
-        while (true)
-        {
-            RetainableByteBuffer b = pool.acquire(capacity - 1, false);
-            assertThat(b.capacity(), Matchers.is(capacity));
-            b = pool.acquire(capacity, false);
-            assertThat(b.capacity(), Matchers.is(capacity));
-
-            if (capacity >= pool.getMaxCapacity())
-                break;
-
-            b = pool.acquire(capacity + 1, false);
-            assertThat(b.capacity(), Matchers.is(capacity * 2));
-
-            capacity = capacity * 2;
-        }
+        ArrayByteBufferPool pool1 = new ArrayByteBufferPool.Quadratic();
+        String dump1 = pool1.dump();
+        assertThat(dump1, containsString("direct size=5\n"));
+        assertThat(dump1, containsString("{capacity=4096,"));
+        assertThat(dump1, containsString("{capacity=8192,"));
+        assertThat(dump1, containsString("{capacity=16384,"));
+        assertThat(dump1, containsString("{capacity=32768,"));
+        assertThat(dump1, containsString("{capacity=65536,"));
+
+        ArrayByteBufferPool pool2 = new ArrayByteBufferPool.Quadratic(100, 800, Integer.MAX_VALUE);
+        String dump2 = pool2.dump();
+        assertThat(dump2, containsString("direct size=4\n"));
+        assertThat(dump2, containsString("{capacity=128,"));
+        assertThat(dump2, containsString("{capacity=256,"));
+        assertThat(dump2, containsString("{capacity=512,"));
+        assertThat(dump2, containsString("{capacity=800,"));
+
+        ArrayByteBufferPool pool3 = new ArrayByteBufferPool.Quadratic(0, 200, Integer.MAX_VALUE);
+        String dump3 = pool3.dump();
+        assertThat(dump3, containsString("direct size=9\n"));
+        assertThat(dump3, containsString("{capacity=1,"));
+        assertThat(dump3, containsString("{capacity=2,"));
+        assertThat(dump3, containsString("{capacity=4,"));
+        assertThat(dump3, containsString("{capacity=8,"));
+        assertThat(dump3, containsString("{capacity=16,"));
+        assertThat(dump3, containsString("{capacity=32,"));
+        assertThat(dump3, containsString("{capacity=64,"));
+        assertThat(dump3, containsString("{capacity=128,"));
+        assertThat(dump3, containsString("{capacity=200,"));
     }
 
     @Test