Re[2]: MMAP issues

From: Peter Zaitsev (pz@spylog.ru)
Date: Tue Nov 27 2001 - 12:54:24 EST


Hello Andrew,

Tuesday, November 27, 2001, 8:44:40 PM, you wrote:

OK. Of course. It's just a few lines length:
Just mention to create any "test.dat" file in the current directory;

#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>

int main()
 {
  int i=0;
  void* p;
  int t;
  int fd;
  
  
  t=time(NULL);
  while(1)
    {
     fd=open("test.dat",O_RDWR);
     if (fd<0)
      {
       puts("Unable to open file !");
       return;
      }
     p=mmap(NULL,4096, PROT_READ | PROT_WRITE , MAP_PRIVATE ,fd ,0);
     if ((int)p==-1)
          {
           printf("Failed %d\n",errno);
           return;
          }
     i++;
     if (i%10000==0)
       {
        printf(" %d Time: %d\n",i,time(NULL)-t);
        t=time(NULL);
       }
     
    }
 }

AM> Peter Zaitsev wrote:
>>
>> Hello ,
>>
>> I'm trying to write a program which uses mmap agressively to mmap
>> files (really it's used as fail safe memory allocator to store data
>> if application failed)
>>

AM> It would really help if you could make your test application available to
AM> the kernel developers.

AM> Thanks.

Additionally the interesting thing is - if I change MMAP params to:
p=mmap(NULL,4096, PROT_READ | PROT_WRITE , MAP_PRIVATE | MAP_ANON ,-1 ,0);

(The only change is mapping done ammoniums instead of mmaping a file
- this increases speed really much and it does not decrease)

-- 
Best regards,
 Peter                            mailto:pz@spylog.ru

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