Atomic operations are expensive, even if there is no contention with other threads. Please don't use them in serial code (this includes std::shared_ptr). Tested on Intel Core i7-5820Kpic.twitter.com/SShUepjp2Y
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Atomic operations are expensive, even if there is no contention with other threads. Please don't use them in serial code (this includes std::shared_ptr). Tested on Intel Core i7-5820Kpic.twitter.com/SShUepjp2Y
My view is: They’re reasonably fast already, but the more we use them, the more the CPU makers will optimize them. So interlock away!
Is there a lot of room for them to get faster? Isn't the lower bound around the cost of a cache miss? We try to avoid cache misses, so why not try to avoid unnecessary interlocked ops too?
A CPU’s speculative execution *could* plow through an interlocked operation or atomic block at full speed, and only backtrack if there’s contention. Speculative concurrency control is the most vital current topic in CPU design.
imo discussing the performance of operations out of specific context is unhelpful
Hypothesis: When we have many cores, we'll want to multithread fine-grained shared-state updates (such as each actor ticks). Library abstractions like transactional vars, atomic blocks, futures, and smart pointers will make this friendly for user code.
Thus we'll make multithreading tractable by millions of normal programmers, but the cost is 100,000,000's of atomics or tsx blocks per core per second.
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