PROBLEM:

We write a benchmark tool in C++ where we want to clear the filesystem memory cache between experiments.

sync
echo 3 > /proc/sys/vm/drop_caches

My question is how can we do this programmatically directly within C++?
SOLUTION 1:

Try this :

sync();

std::ofstream ofs("/proc/sys/vm/drop_caches");
ofs << "3" << std::endl;

SOLUTION 2:

Try this sample code:

int fd;
char* data = "3";

sync();
fd = open("/proc/sys/vm/drop_caches", O_WRONLY);
write(fd, data, sizeof(char));
close(fd);

Clean page cache in linux programmatically

• You are probably stuck with opening the file /proc/sys/vm/drop_caches, writing 1 to it and close it again. There is no dedicated syscall for that operation.
  bash code

  sync();
  int fd = open("/proc/sys/vm/drop_caches", O_WRONLY);
  write(fd, "1", 1);
  close(fd);

  Depending on what you try to achieve, the (optional) preceding sync() can help free some more memory.