为什么mmap无法分配内存? [英] Why mmap cannot allocate memory?
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问题描述
我以root特权运行该程序,但它一直抱怨mmap无法分配内存.代码段如下:
I ran the program with root priviledge but it keeps complaining that mmap cannot allocate memory. Code snippet is below:
#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, 0);
if (buf == MAP_FAILED) {
perror("mmap");
exit(1);
}
...}
硬件:我有8G RAM.处理器是常春藤
Hardware: I have 8G RAM. Processor is 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
perror的输出
mmap: Cannot allocate memory
还添加了一行以打印errno
Also added one line to print errno
printf("something is wrong: %d\n", errno);
但是输出是:
something is wrong: 12
来自/proc/meminfo的大量tlb相关信息
EDIT 2: The huge tlb related information from /proc/meminfo
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
推荐答案
好吧,如 Documentation/vm/hugetlspage.txt 建议,做
echo 20 > /proc/sys/vm/nr_hugepages
解决了问题.在Ubuntu 14.04上测试.检查为什么我也无法使用mmap映射内存.
solved the problem. Tested on ubuntu 14.04. Check Why I can't map memory with mmap also.
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