vmalloc,kmalloc,get_free_page,kmem_cache_create分配内存实例

//All right revsered by yoki2009

//mailto:imj040144@tom.com

////微出版 www.epube.biz 相信梦想无界

#include <linux/mm.h>

#include <linux/sched.h>

#include <linux/jiffies.h>

#include <linux/vmalloc.h>

#include <linux/delay.h>

/*

vmalloc,kmalloc,get_free_page,kmem_cache_create

vmalloc与kmalloc区别在于起始地址不同,kmalloc分配的内存处于3GB~high_memory之间,这段内核

空间与物理内存的映射一一对应,而vmalloc分配的内存在VMALLOCSTAERT~4GB之间,这段非连续内存

区映射到物理内存也可能是非连续的,vmalloc分配的物理地址无需连续,而kmalloc确保页在物理上

是连续的

*/

unsigned char * vmchar;

unsigned char * kmchar;

unsigned char * m_free_pages;

struct kmem_cache_t * kmem_cache;

unsigned char * slabchar;

static int __init mem_test_init(void)

{

printk("Hello, world/n");

//vmalloc test

//分配虚拟内存,也就是位于高端128M内存

printk("[vmalloc] Enter Jiffy %ld/n",jiffies);

vmchar = (unsigned char *)vmalloc(16*1024*1024);

if (!vmchar)

{

printk("Error on vmalloc/n");

return -1;

}

memset(vmchar,0,16*1024*1024);

printk("vmalloc address : %x/n",vmchar);

//kmalloc test

//kmalloc分配的低端内存,直接映射到物理内存

printk("[kmalloc] Enter Jiffy %ld/n",jiffies);

//kmalloc最大只能开辟128k

kmchar = (unsigned char *)kmalloc(PAGE_SIZE*32,GFP_KERNEL);

if (!kmchar)

{

printk("Error on kmalloc/n");

return -1;

}

memset(kmchar,0,PAGE_SIZE*32);

printk("kmalloc address : %x/n",kmchar);

printk("[kmalloc] Exit Jiffy %ld/n",jiffies);

//get_free_page test

//也是使用kmalloc分配的内存区域

printk("[get_free_pages] Enter Jiffy %ld/n",jiffies);

m_free_pages = (unsigned char *)__get_free_pages(GFP_KERNEL,2);

if (!m_free_pages)

{

printk("Error on m_free_pages/n");

return -1;

}

memset(m_free_pages,'a',PAGE_SIZE*2);

/*

while(m_free_pages)

{

printk("[get_free_pages] address == %x/n",m_free_pages>>PAGE_SHIFT);

}

*/

printk("get_free_pages address : %x/n",m_free_pages);

printk("[get_free_pages] Exit Jiffy %ld/n",jiffies);

//slab alloc test

//使用后备高速缓存,对于反复地分配很多同一大小的内存块使用Slab分配方式

printk("[Slab] Enter Jiffy %ld/n",jiffies);

kmem_cache = kmem_cache_create("slab_cache",4,0,SLAB_HWCACHE_ALIGN,NULL);

if (!kmem_cache)

{

printk("Error on Slab/n");

return -1;

}

slabchar = kmem_cache_alloc(kmem_cache,GFP_KERNEL);

if (!slabchar)

{

printk("Error on alloc slab cache/n");

return -1;

}

memset(slabchar,0,4);

printk("Slab address : %x/n",slabchar);

kmem_cache_free(kmem_cache,slabchar);

kmem_cache_destroy(kmem_cache);

printk("[Slab] Exit Jiffy %ld/n",jiffies);

return 0;

}

static void __exit mem_test_exit(void)

{

vfree(vmchar);

kfree(kmchar);

free_pages(m_free_pages,2);

}

module_init(mem_test_init);

module_exit(mem_test_exit);