PoolThreadCache

Constructor

private final MemoryRegionCache<byte[]>[] tinySubPageHeapCaches;
private final MemoryRegionCache<byte[]>[] smallSubPageHeapCaches;
private final MemoryRegionCache<ByteBuffer>[] tinySubPageDirectCaches;
private final MemoryRegionCache<ByteBuffer>[] smallSubPageDirectCaches;
private final MemoryRegionCache<byte[]>[] normalHeapCaches;
private final MemoryRegionCache<ByteBuffer>[] normalDirectCaches;

//..
tinySubPageDirectCaches = createSubPageCaches(
        tinyCacheSize, PoolArena.numTinySubpagePools, SizeClass.Tiny);
smallSubPageDirectCaches = createSubPageCaches(
        smallCacheSize, directArena.numSmallSubpagePools, SizeClass.Small);

numShiftsNormalDirect = log2(directArena.pageSize);
normalDirectCaches = createNormalCaches(
        normalCacheSize, maxCachedBufferCapacity, directArena);
//...

The key point is that three sizes of MemoryRegionCache are created: tiny, small, and normal.