My LINUX notes: Memory allocated in the kernel module

My LINUX notes: memory allocation in the kernel module-general Linux technology-Linux programming and kernel information. For details, see below. There are many methods and functions to allocate memory in the kernel module:

1. kmalloc (), which is the most commonly used function. It is fast and physically continuous in the allocated content, but generally, the maximum memory size it can allocate is kb.

2. _ get_free_pages () is used to allocate memory for specified consecutive pages. The property is the same as kmalloc () but more consecutive physical memory can be allocated. Of course, it is the same as kmalloc, the returned value is also the kernel virtual address.

3. vmalloc (), the memory allocated by this function may be physically discontinuous. The memory allocated by this function is not only slightly inefficient but cannot be used for DMA transmission by external devices, it is not recommended to use it in the kernel module. It is recommended only when a large buffer is allocated and used only in the software. Vmalloc () cannot be used in atomic context.