整页Malloc [英] Full Page Malloc
问题描述
我正在尝试通过一次使用整个页面来优化程序的内存分配.
I am trying to optimize the memory allocation of my program by using entire pages at a time.
我正在抓取这样的页面大小:sysconf(_SC_PAGESIZE);，然后正在计算将要放入页面的元素总数，例如:elements=pageSize/sizeof(Node);
I am grabbing the page size like this: sysconf(_SC_PAGESIZE); and am then calculating the total number of elements that will fit in a page like this: elements=pageSize/sizeof(Node);
我的想法是，当我实际去分配内存时，我会使用malloc(elements*sizeof(Node));似乎sifeof(Node)的乘法和除法会抵消，但是对于整数除法，我不认为那是案子.
My thinking was that when I actually go to malloc my memory I would use malloc(elements*sizeof(Node)); It seems like the multiplication and division of sifeof(Node) would cancel out, but with integer division, I do not believe that that is the case.
这是一次一次分配整个页面的最佳方法吗?
Is this the best way to malloc an entire page at a time?
谢谢
推荐答案
malloc函数没有页面大小的任何概念.除非您还要分配与页面边界对齐的页面，否则以这种方式调用malloc不会有任何好处.只需malloc所需的任意数量的元素，就不必再担心微优化几乎肯定不会给您带来任何好处的东西了.
The malloc function doesn't have any concept of pagesize. Unless you are allocating pages that are ALSO aligned to a page-boundary, you will not get ANY benefit from calling malloc in this way. Just malloc as many elements as you need, and stop worrying about micro-optimising something that almost certainly won't give you any benefit at all.
是的，Linux内核一直在做这样的事情.这样做有两个原因:
Yes, the Linux kernel does things like this all the time. There are two reasons for that:
- 您不希望分配比页面大的块，因为这会大大增加分配失败的风险.
- 内核分配是按页进行的，而不是像C库那样一次分配大量内存，然后将其拆分为较小的组件.
如果您确实要分配页面大小的内存，请使用sysconf(_SC_PAGESIZE)的结果作为您的大小参数.但是几乎可以肯定，您的分配跨越了两个页面.
If you really want to allocate page-size amount of memory, then use the result from sysconf(_SC_PAGESIZE) as your size argument. But it is almost certain that your allocation straddles two pages.
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