| /* |
| * This file is part of the Jikes RVM project (http://jikesrvm.org). |
| * |
| * This file is licensed to You under the Eclipse Public License (EPL); |
| * You may not use this file except in compliance with the License. You |
| * may obtain a copy of the License at |
| * |
| * http://www.opensource.org/licenses/eclipse-1.0.php |
| * |
| * See the COPYRIGHT.txt file distributed with this work for information |
| * regarding copyright ownership. |
| */ |
| package org.mmtk.utility.alloc; |
| |
| import org.mmtk.policy.SegregatedFreeListSpace; |
| import org.mmtk.utility.*; |
| |
| import org.vmmagic.pragma.*; |
| import org.vmmagic.unboxed.*; |
| |
| /** |
| * This abstract class implements the fast past for a segregated free list. |
| */ |
| @Uninterruptible |
| public abstract class SegregatedFreeList<S extends SegregatedFreeListSpace> extends Allocator implements Constants { |
| |
| /**************************************************************************** |
| * |
| * Instance variables |
| */ |
| |
| /** The space */ |
| protected final S space; |
| |
| /** The current free lists for the size classes */ |
| protected final AddressArray freeList; |
| |
| /**************************************************************************** |
| * |
| * Initialization |
| */ |
| |
| /** |
| * Constructor |
| * |
| * @param space The space with which this allocator will be associated |
| */ |
| public SegregatedFreeList(S space) { |
| this.space = space; |
| this.freeList = AddressArray.create(sizeClassCount()); |
| } |
| |
| /** |
| * Return the space this allocator is currently bound to. |
| * |
| * @return The Space. |
| */ |
| protected final S getSpace() { |
| return this.space; |
| } |
| |
| /**************************************************************************** |
| * |
| * Allocation |
| */ |
| |
| /** |
| * Allocate <code>bytes</code> contiguous bytes of zeroed memory.<p> |
| * |
| * This code implements the fast path, and on failure delegates to the slow path. |
| * |
| * @param bytes The size of the object to occupy this space, in bytes. |
| * @param align The requested alignment. |
| * @param offset The alignment offset. |
| * @return The address of the first word or zero on failure |
| */ |
| @Inline |
| public final Address alloc(int bytes, int align, int offset) { |
| int alignedBytes = getMaximumAlignedSize(bytes, align); |
| int sizeClass = getSizeClass(alignedBytes); |
| Address cell = freeList.get(sizeClass); |
| if (!cell.isZero()) { |
| freeList.set(sizeClass, cell.loadAddress()); |
| /* Clear the free list link */ |
| cell.store(Address.zero()); |
| if (alignedBytes != bytes) { |
| /* Ensure aligned as requested. */ |
| cell = alignAllocation(cell, align, offset); |
| } |
| return cell; |
| } |
| return allocSlow(bytes, align, offset); |
| } |
| |
| /** |
| * The number of distinct size classes. |
| * |
| * NOTE: For optimal performance this call must be implemented in a way |
| * it can be inlined and optimized within the allocation sequence. |
| */ |
| @Inline |
| private int sizeClassCount() { |
| return SegregatedFreeListSpace.sizeClassCount(); |
| } |
| |
| /** |
| * Get the size class for a given number of bytes. |
| * |
| * NOTE: For optimal performance this call must be implemented in a way |
| * it can be inlined and optimized within the allocation sequence. |
| * |
| * @param bytes The number of bytes required to accommodate the object |
| * @return The size class capable of accommodating the allocation request. |
| */ |
| @Inline |
| private int getSizeClass(int bytes) { |
| return space.getSizeClass(bytes); |
| } |
| } |