subpage = new PoolSubpage(head, this, id, runOffset(id), pageSize, normCapacity);

PoolSubpage(PoolSubpage head, PoolChunk chunk, int memoryMapIdx, int runOffset, int pageSize, int elemSize) {this.chunk = chunk; this.memoryMapIdx = memoryMapIdx; this.runOffset = runOffset; this.pageSize = pageSize; bitmap = new long[pageSize >>> 10]; init(head, elemSize); }

void init(PoolSubpage head, int elemSize) {doNotDestroy = true; this.elemSize = elemSize; if (elemSize != 0) {maxNumElems = numAvail = pageSize / elemSize; nextAvail = 0; bitmapLength = maxNumElems >>> 6; if ((maxNumElems & 63) != 0) {bitmapLength ++; }for (int i = 0; i < bitmapLength; i ++) {//bitmap标识哪个子page被分配//0标识未分配, 1表示已分配bitmap [i] = 0; }}//加到arena里面addToPool(head); }

maxNumElems = numAvail = pageSize / elemSize

private void addToPool(PoolSubpage head) {assert prev == null && next == null; prev = head; next = head.next; next.prev = this; head.next = this; }

private long allocateSubpage(int normCapacity) {PoolSubpage head = arena.findSubpagePoolHead(normCapacity); synchronized (head) {int d = maxOrder; //表示在第11层分配节点int id = allocateNode(d); if (id < 0) {return id; }//获取初始化的subpagefinal PoolSubpage[] subpages = this.subpages; final int pageSize = this.pageSize; freeBytes -= pageSize; //表示第几个subpageIdxint subpageIdx = subpageIdx(id); PoolSubpage subpage = subpages[subpageIdx]; if (subpage == null) {//如果subpage为空subpage = new PoolSubpage(head, this, id, runOffset(id), pageSize, normCapacity); //则将当前的下标赋值为subpagesubpages[subpageIdx] = subpage; } else {subpage.init(head, normCapacity); }//取出一个子pagereturn subpage.allocate(); }}

long allocate() { if (elemSize == 0) {return toHandle(0); }if (numAvail == 0 || !doNotDestroy) {return -1; }//取一个bitmap中可用的id(绝对id)final int bitmapIdx = getNextAvail(); //除以64(bitmap的相对下标)int q = bitmapIdx >>> 6; //除以64取余, 其实就是当前绝对id的偏移量int r = bitmapIdx & 63; assert (bitmap[q] >>> r & 1) == 0; //当前位标记为1bitmap[q] |= 1L << r; //如果可用的子page为0//可用的子page-1if (-- numAvail == 0) {//则移除相关子pageremoveFromPool(); }//bitmapIdx转换成handlerreturn toHandle(bitmapIdx); }

final int bitmapIdx = getNextAvail();

private int getNextAvail() {//nextAvail=0int nextAvail = this.nextAvail; if (nextAvail >= 0) {//一个子page被释放之后, 会记录当前子page的bitmapIdx的位置, 下次分配可以直接通过bitmapIdx拿到一个子pagethis.nextAvail = -1; return nextAvail; }return findNextAvail(); }

private int findNextAvail() {//当前long数组final long[] bitmap = this.bitmap; //获取其长度final int bitmapLength = this.bitmapLength; for (int i = 0; i < bitmapLength; i ++) {//第i个long bits = bitmap[i]; //!=-1 说明64位没有全部占满if (~bits != 0) {//找下一个节点return findNextAvail0(i, bits); }}return -1; }

private int findNextAvail0(int i, long bits) {//多少份final int maxNumElems = this.maxNumElems; //乘以64, 代表当前long的第一个下标final int baseVal = i << 6; //循环64次(指代当前的下标)for (int j = 0; j < 64; j ++) {//第一位为0(如果是2的倍数, 则第一位就是0)if ((bits & 1) == 0) {//这里相当于加, 将i*64之后加上j, 获取绝对下标int val = baseVal | j; //小于块数(不能越界)if (val < maxNumElems) {return val; } else {break; }}//当前下标不为0//右移一位bits >>>= 1; }return -1; }

long allocate() { if (elemSize == 0) {return toHandle(0); }if (numAvail == 0 || !doNotDestroy) {return -1; }//取一个bitmap中可用的id(绝对id)final int bitmapIdx = getNextAvail(); //除以64(bitmap的相对下标)int q = bitmapIdx >>> 6; //除以64取余, 其实就是当前绝对id的偏移量int r = bitmapIdx & 63; assert (bitmap[q] >>> r & 1) == 0; //当前位标记为1bitmap[q] |= 1L << r; //如果可用的子page为0//可用的子page-1if (-- numAvail == 0) {//则移除相关子pageremoveFromPool(); }//bitmapIdx转换成handlerreturn toHandle(bitmapIdx); }

private long toHandle(int bitmapIdx) {return 0x4000000000000000L | (long) bitmapIdx << 32 | memoryMapIdx; }

private synchronized void allocateNormal(PooledByteBuf buf, int reqCapacity, int normCapacity) {//首先在原来的chunk上进行内存分配(1)if (q050.allocate(buf, reqCapacity, normCapacity) || q025.allocate(buf, reqCapacity, normCapacity) ||q000.allocate(buf, reqCapacity, normCapacity) || qInit.allocate(buf, reqCapacity, normCapacity) ||q075.allocate(buf, reqCapacity, normCapacity)) {++allocationsNormal; return; }//创建chunk进行内存分配(2)PoolChunk c = newChunk(pageSize, maxOrder, pageShifts, chunkSize); long handle = c.allocate(normCapacity); ++allocationsNormal; assert handle > 0; //初始化byteBuf(3)c.initBuf(buf, handle, reqCapacity); qInit.add(c); }

void initBuf(PooledByteBuf buf, long handle, int reqCapacity) {int memoryMapIdx = memoryMapIdx(handle); //bitmapIdx是后面分配subpage时候使用到的int bitmapIdx = bitmapIdx(handle); if (bitmapIdx == 0) {byte val = value(memoryMapIdx); assert val == unusable : String.valueOf(val); //runOffset(memoryMapIdx):偏移量//runLength(memoryMapIdx):当前节点的长度buf.init(this, handle, runOffset(memoryMapIdx), reqCapacity, runLength(memoryMapIdx), arena.parent.threadCache()); } else {initBufWithSubpage(buf, handle, bitmapIdx, reqCapacity); }}

private void initBufWithSubpage(PooledByteBuf buf, long handle, int bitmapIdx, int reqCapacity) {assert bitmapIdx != 0; int memoryMapIdx = memoryMapIdx(handle); PoolSubpage subpage = subpages[subpageIdx(memoryMapIdx)]; assert subpage.doNotDestroy; assert reqCapacity <= subpage.elemSize; buf.init(this, handle, runOffset(memoryMapIdx) + (bitmapIdx & 0x3FFFFFFF) * subpage.elemSize, reqCapacity, subpage.elemSize, arena.parent.threadCache()); }

private static int memoryMapIdx(long handle) {return (int) handle; }

void init(PoolChunk chunk, long handle, int offset, int length, int maxLength, PoolThreadCache cache) {//初始化assert handle >= 0; assert chunk != null; //在哪一块内存上进行分配的this.chunk = chunk; //这一块内存上的哪一块连续内存this.handle = handle; memory = chunk.memory; //偏移量this.offset = offset; this.length = length; this.maxLength = maxLength; tmpNioBuf = null; this.cache = cache; }

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