我用root权限运行程序,但它一直在抱怨mmap无法分配内存.代码段如下：
#define PROTECTION (PROT_READ | PROT_WRITE)
#define LENGTH (4*1024)
#ifndef MAP_HUGETLB
#define MAP_HUGETLB 0x40000
#endif
#define ADDR (void *) (0x0UL)
#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
int main (int argc,char *argv[]){
...
// allocate a buffer with the same size as the LLC using huge pages
buf = mmap(ADDR,LENGTH,PROTECTION,FLAGS,0);
if (buf == MAP_Failed) {
perror("mmap");
exit(1);
}
...}
硬件：我有8G内存.处理器是ivybridge
Uname输出：
Linux mymachine 3.13.0-43-generic #72-Ubuntu SMP Mon Dec 8 19:35:06 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
编辑1：perror的输出
mmap: Cannot allocate memory
还添加了一行来打印errno
printf("something is wrong: %d\n",errno);
但输出是：
something is wrong: 12
编辑2：来自/ proc / meminfo的巨大的tlb相关信息
HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB
解决方法
好吧,正如
Documentation/vm/hugetlspage.txt建议的那样
echo 20 > /proc/sys/vm/nr_hugepages
解决了这个问题.在ubuntu 14.04上测试过.检查Why I can’t map memory with mmap.
