What happens when you run out of ram with mlockall set?

Question

I am working on a C ++ application that requires a large amount of memory to run in batch. (> 20 GB)

Some of my clients work with memory limitations, where sometimes the OS starts a swap, and the total operating time doubles or worsens.

I read that I can use mlockall so that the process is not replaced. What happens when the memory requirements of a process approach or exceed the available physical memory in this way?

I think the answer may be OS specific, so please list the OS in your answer.

Answer 1

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Answer 2

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script:

#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv){
  int r = 0;
  int count = 0;
  char *buf;

  printf("Locking...\n");
  r = mlockall(MCL_FUTURE);
  if(r){
    printf("Error: %d\n", r);
    exit(1);
  }

  while(1){
    buf = malloc(1000);
    if(!buf){
      printf("Failed to allocate after %d iterations\n", count);
      exit(0);
    }
    count++;
  }

  return 0;
}

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Answer 3

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