IBM User Guide for Java V7 on Windows > IBM SDK for Java > The collector and the allocator > Allocation

Cache allocation

Cache allocation is specifically designed to deliver the best possible allocation performance for small objects.

Objects are allocated directly from a thread local allocation buffer that the thread has previously allocated from the heap. A new object is allocated from this cache without the need to grab the heap lock; therefore, cache allocation is very efficient.

All objects less than 512 bytes (768 bytes on 64-bit JVMs) are allocated from the cache. Larger objects are allocated from the cache if they can be contained in the existing cache; if not a locked heap allocation is performed.

The cache block is sometimes called a thread local heap (TLH). The size of the TLH varies from 512 bytes (768 on 64-bit JVMs) to 128 KB, depending on the allocation rate of the thread. Threads which allocate lots of objects are given larger TLHs to further reduce contention on the heap lock.

Parent: Allocation

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