MMAP VS SBRK，性能比较 [英] mmap vs sbrk, performance comparison

问题描述

哪个这些调用的平均为快？我听说MMAP是较小的分配速度更快，但我还没有听说过的任何比较。对这些性能的任何信息就好了。

Which of these calls is faster on average? I've heard that mmap is faster for smaller allocations but I haven't heard a comparison of either. Any information on performance for these would be nice.

推荐答案

您应该用特殊的实现（如的Linux ）标签，这一点，因为答案肯定通过实施不同而不同。现在我假设的Linux，因为它是最流行的。

You should tag this with a particular implementation (like linux) since the answer surely varies by implementation. For now I'll assume Linux since it's the most popular.

随着中说， BRK 在理论上更加优化的，并在实践运行我的机器上快10％左右。分配一个页面，这些都是我得到的时间：

With that said, brk is in theory more optimizable, and in practice it runs about 10% faster on my machine. Allocating one page, these are the times I get:

• BRK ：分钟2550次，典型的2650个周期


• MMAP ：2700分钟周期，典型的2800个周期

• brk: min 2550 cycles, typical 2650 cycles
• mmap: min 2700 cycles, typical 2800 cycles

我记得，在能够跳过锁定 MMAP 信号，这可以解释的 BRK 行听到的东西的差异。

I remember hearing something along the lines of brk being able to skip locking the mmap semaphore, which would explain the discrepancy.

注意：我这些时间调整我的测试，以一个虚拟的电话之前，定时更新后，确保了code都将是在缓存

Note: I updated these times after adjusting my test to make a dummy calls prior to timing, to ensure that the code would all be in the cache.

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