293 lines
8.1 KiB
Java
293 lines
8.1 KiB
Java
/*
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* Copyright 2012 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.net5.buffer;
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import static io.net5.buffer.PoolChunk.RUN_OFFSET_SHIFT;
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import static io.net5.buffer.PoolChunk.SIZE_SHIFT;
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import static io.net5.buffer.PoolChunk.IS_USED_SHIFT;
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import static io.net5.buffer.PoolChunk.IS_SUBPAGE_SHIFT;
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import static io.net5.buffer.SizeClasses.LOG2_QUANTUM;
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final class PoolSubpage<T> implements PoolSubpageMetric {
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final PoolChunk<T> chunk;
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private final int pageShifts;
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private final int runOffset;
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private final int runSize;
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private final long[] bitmap;
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PoolSubpage<T> prev;
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PoolSubpage<T> next;
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boolean doNotDestroy;
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int elemSize;
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private int maxNumElems;
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private int bitmapLength;
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private int nextAvail;
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private int numAvail;
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// TODO: Test if adding padding helps under contention
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//private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
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/** Special constructor that creates a linked list head */
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PoolSubpage() {
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chunk = null;
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pageShifts = -1;
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runOffset = -1;
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elemSize = -1;
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runSize = -1;
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bitmap = null;
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}
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PoolSubpage(PoolSubpage<T> head, PoolChunk<T> chunk, int pageShifts, int runOffset, int runSize, int elemSize) {
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this.chunk = chunk;
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this.pageShifts = pageShifts;
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this.runOffset = runOffset;
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this.runSize = runSize;
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this.elemSize = elemSize;
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bitmap = new long[runSize >>> 6 + LOG2_QUANTUM]; // runSize / 64 / QUANTUM
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doNotDestroy = true;
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if (elemSize != 0) {
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maxNumElems = numAvail = runSize / elemSize;
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nextAvail = 0;
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bitmapLength = maxNumElems >>> 6;
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if ((maxNumElems & 63) != 0) {
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bitmapLength ++;
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}
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for (int i = 0; i < bitmapLength; i ++) {
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bitmap[i] = 0;
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}
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}
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addToPool(head);
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}
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/**
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* Returns the bitmap index of the subpage allocation.
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*/
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long allocate() {
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if (numAvail == 0 || !doNotDestroy) {
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return -1;
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}
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final int bitmapIdx = getNextAvail();
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int q = bitmapIdx >>> 6;
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int r = bitmapIdx & 63;
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assert (bitmap[q] >>> r & 1) == 0;
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bitmap[q] |= 1L << r;
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if (-- numAvail == 0) {
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removeFromPool();
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}
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return toHandle(bitmapIdx);
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}
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/**
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* @return {@code true} if this subpage is in use.
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* {@code false} if this subpage is not used by its chunk and thus it's OK to be released.
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*/
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boolean free(PoolSubpage<T> head, int bitmapIdx) {
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if (elemSize == 0) {
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return true;
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}
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int q = bitmapIdx >>> 6;
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int r = bitmapIdx & 63;
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assert (bitmap[q] >>> r & 1) != 0;
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bitmap[q] ^= 1L << r;
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setNextAvail(bitmapIdx);
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if (numAvail ++ == 0) {
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addToPool(head);
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/* When maxNumElems == 1, the maximum numAvail is also 1.
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* Each of these PoolSubpages will go in here when they do free operation.
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* If they return true directly from here, then the rest of the code will be unreachable
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* and they will not actually be recycled. So return true only on maxNumElems > 1. */
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if (maxNumElems > 1) {
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return true;
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}
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}
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if (numAvail != maxNumElems) {
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return true;
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} else {
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// Subpage not in use (numAvail == maxNumElems)
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if (prev == next) {
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// Do not remove if this subpage is the only one left in the pool.
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return true;
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}
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// Remove this subpage from the pool if there are other subpages left in the pool.
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doNotDestroy = false;
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removeFromPool();
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return false;
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}
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}
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private void addToPool(PoolSubpage<T> head) {
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assert prev == null && next == null;
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prev = head;
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next = head.next;
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next.prev = this;
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head.next = this;
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}
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private void removeFromPool() {
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assert prev != null && next != null;
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prev.next = next;
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next.prev = prev;
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next = null;
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prev = null;
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}
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private void setNextAvail(int bitmapIdx) {
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nextAvail = bitmapIdx;
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}
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private int getNextAvail() {
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int nextAvail = this.nextAvail;
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if (nextAvail >= 0) {
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this.nextAvail = -1;
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return nextAvail;
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}
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return findNextAvail();
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}
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private int findNextAvail() {
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final long[] bitmap = this.bitmap;
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final int bitmapLength = this.bitmapLength;
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for (int i = 0; i < bitmapLength; i ++) {
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long bits = bitmap[i];
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if (~bits != 0) {
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return findNextAvail0(i, bits);
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}
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}
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return -1;
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}
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private int findNextAvail0(int i, long bits) {
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final int maxNumElems = this.maxNumElems;
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final int baseVal = i << 6;
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for (int j = 0; j < 64; j ++) {
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if ((bits & 1) == 0) {
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int val = baseVal | j;
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if (val < maxNumElems) {
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return val;
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} else {
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break;
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}
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}
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bits >>>= 1;
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}
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return -1;
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}
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private long toHandle(int bitmapIdx) {
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int pages = runSize >> pageShifts;
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return (long) runOffset << RUN_OFFSET_SHIFT
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| (long) pages << SIZE_SHIFT
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| 1L << IS_USED_SHIFT
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| 1L << IS_SUBPAGE_SHIFT
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| bitmapIdx;
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}
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@Override
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public String toString() {
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final boolean doNotDestroy;
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final int maxNumElems;
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final int numAvail;
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final int elemSize;
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if (chunk == null) {
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// This is the head so there is no need to synchronize at all as these never change.
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doNotDestroy = true;
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maxNumElems = 0;
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numAvail = 0;
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elemSize = -1;
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} else {
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synchronized (chunk.arena) {
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if (!this.doNotDestroy) {
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doNotDestroy = false;
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// Not used for creating the String.
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maxNumElems = numAvail = elemSize = -1;
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} else {
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doNotDestroy = true;
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maxNumElems = this.maxNumElems;
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numAvail = this.numAvail;
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elemSize = this.elemSize;
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}
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}
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}
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if (!doNotDestroy) {
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return "(" + runOffset + ": not in use)";
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}
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return "(" + runOffset + ": " + (maxNumElems - numAvail) + '/' + maxNumElems +
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", offset: " + runOffset + ", length: " + runSize + ", elemSize: " + elemSize + ')';
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}
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@Override
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public int maxNumElements() {
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if (chunk == null) {
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// It's the head.
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return 0;
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}
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synchronized (chunk.arena) {
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return maxNumElems;
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}
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}
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@Override
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public int numAvailable() {
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if (chunk == null) {
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// It's the head.
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return 0;
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}
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synchronized (chunk.arena) {
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return numAvail;
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}
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}
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@Override
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public int elementSize() {
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if (chunk == null) {
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// It's the head.
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return -1;
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}
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synchronized (chunk.arena) {
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return elemSize;
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}
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}
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@Override
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public int pageSize() {
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return 1 << pageShifts;
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}
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void destroy() {
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if (chunk != null) {
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chunk.destroy();
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}
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}
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}
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