#include <linux/slab.h>
void *kmalloc(size_t size, int flags);
Kmalloc分配一段未清0的连续物理内存页，并返回虚存地址。有点是快，并且可指定flag，如DMA内存，高地址区域内存等。缺点是不能分配大于128KB（处于跨平台考虑），几个重要的flag：
GFP_ATOMIC
Used to allocate memory from interrupt handlers and other code outside of a process context. Never sleeps.
GFP_KERNEL
Normal allocation of kernel memory. May sleep.
GFP_USER
Used to allocate memory for user-space pages; it may sleep.
GFP_HIGHUSER
Like GFP_USER, but allocates from high memory, if any. High memory is described in the next subsection.
* slab allocator（lookaside cache）
从Memcached的实现知道有这么一个内存管理策略，其显着特点是分配一组相同大小的内存块作为内存池，其实现对应于源代码中的<linux/slab.h>和mm/slab.c。
Prototype:
#include <linux/malloc.h>
kmem_cache_t *kmem_cache_create(char *name, size_t size, size_t offset,
unsigned long flags, constructor( ), destructor( ));
int kmem_cache_destroy(kmem_cache_t *cache);
/proc/slabinfo
A virtual file containing statistics on slab cache usage.
*__get_free_pages
Prototype:
_ _get_free_pages(unsigned int flags, unsigned int order);