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    <p>In <em>example 1</em>, CPU first needs to access the pointer itself, then the actual object.</p> <ul> <li>Pointer is on the stack which gives it a good chance it is already in data cache due good locality with other variables on the stack. It might even be in register.</li> <li>It is unusual for the object to be on the same stack frame as pointer - it is either on the heap (on "random" location) or on a shallower stack frame, and there is a possibility it is no longer in d-cache so you are more likely to pay memory latency penalty.</li> </ul> <p>In <em>example 2</em>, CPU can access the object directly, which is on the stack so it has a good chance it is already cached due good locality with to other variables on the stack.</p> <p>All the memory locations accessed will end-up in d-cache until replaced by more recently accessed locations. How exactly is d-cache maintained and synchronized between different cores in multi-core CPU is implementation detail of a particular CPU and involves "cache lines" (typically 64-bit blocks that are "units" of caching) and various cache coherence protocols.</p> <p>That being said, you should be aware of a serious degradation of performance in multi-threaded environment that may be consequence of these implementation details, called <a href="http://drdobbs.com/go-parallel/article/showArticle.jhtml?articleID=217500206" rel="nofollow">false sharing</a>.</p> <p>Generally speaking, chasing pointers is slower than just accessing memory linearly, because it has worse locality (so caches are less effective) and worse predictability (so CPU cannot utilize prefetching effectively).</p>
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    1. COWhat if pSomeObject and variable are in distant places of memory? Can they be in cache at the same time or one after another?
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    2. CO@TiagoCosta Yes they can (be in cache at the same time). They will be in different "cache lines".
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    3. COOh I see... Can you recommend me some book that explains how caches work? I've read Intel programming guidelines but they aren't very helpful because they're too high-level
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