问题描述
我试图了解 memalign() 和 posix_memalign() 函数的作用.阅读可用的文档没有帮助.
I'm trying to understand what functions memalign() and posix_memalign() do. Reading the available documentation didn't help.
有人可以帮助我了解它的工作原理以及它的用途吗?或者，也许提供一个使用示例?
Can someone help me understand how it works and what is it used for? Or, perhaps provide a usage example?
我想了解 linux 内存是如何工作的，我需要编写自己的简单内存池(低碎片堆).
I'm trying to understand how linux memory works, I need to write my own simple memory pool (low-fragmentation heap).
推荐答案
而 malloc 为您提供了一块可以任意对齐的内存(唯一的要求是它必须为最大实现支持的原始类型)，posix_memalign 为您提供一块内存，保证具有所请求的对齐.
Whereas malloc gives you a chunk of memory that could have any alignment (the only requirement is that it must be aligned for the largest primitive type that the implementation supports), posix_memalign gives you a chunk of memory that is guaranteed to have the requested alignment.
所以例如的结果posix_memalign(&p, 32, 128) 将是一个 128 字节的内存块，其起始地址保证是 32 的倍数.
So the result of e.g. posix_memalign(&p, 32, 128) will be a 128-byte chunk of memory whose start address is guaranteed to be a multiple of 32.
这对于需要遵守特定对齐方式的内存的各种低级操作(例如使用 SSE 指令或 DMA)非常有用.
This is useful for various low-level operations (such as using SSE instructions, or DMA), that require memory that obeys a particular alignment.
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