[perf-discuss] mmap problem

[love_code meta]

Hi All
   
  Now I 'm testing mmap function, and my pagesize is 4k bytes.  After mapping 
8k virtual memory, by dtrace I find there is only one pagefault when I access 
memory like that s[0] , s[4096].
   
  The following is my test spteps.
  1. fd = open("/var/tmp/mmap.file", O_RDWR);
  2. I'm sure fd is validate. then  
      s = (char *)mmap(NULL, 8192,
     PROT_READ | PROT_WRITE,
      MAP_PRIVATE,
     fd, 0L);
  3. for (i =0; i < 8192; i +=4096)
              a=s[i];
   
  Based on my knowledge, the step 3 should has two pagefault traps. because our 
pagesize is 4k, correct? 
   
   
  Thanks,
  Ma Ling



       
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