Test of forking (creating lot of child processes) at Linux

CMakeLists.txt

# Main CMakeFile.txt
 
# Minimal version of CMake
cmake_minimum_required (VERSION 2.6)
 
# Build type
if (NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
	message(STATUS "Setting build type to 'Debug' as none was specified.")
	set(CMAKE_BUILD_TYPE Debug CACHE STRING "Choose the type of build." FORCE)
	# Set the possible values of build type for cmake-gui
	set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release")
endif ()
 
# Define project name
project (fork-test)
 
# Source code for fork-test
set (fork-test_src fork-test.c)
 
# Compiler flags
if (CMAKE_COMPILER_IS_GNUCC)
	set (CMAKE_C_FLAGS "-D_REETRANT -Wall -Wextra -pedantic -Wno-long-long")
	if (CMAKE_BUILD_TYPE STREQUAL "Debug")
		set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -ggdb -O0")
	elseif( CMAKE_BUILD_TYPE STREQUAL "Release" )
		set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DNDEBUG -O3 -fno-strict-aliasing")
	endif ()
endif (CMAKE_COMPILER_IS_GNUCC)
 
# Set up fork-test executable
add_executable (fork-test ${fork-test_src})

fork-test.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>

#define MICROSECONDS_IN_SECOND 1000000
#define BUFF_SIZE 65535	/* bytes */
#define TIME_DELAY 1	/* seconds */

int main(int argc, char const *argv[])
{
	struct timeval start_tv, end_tv;
	int count, ret, i, proc_num = 10;
	long int diff_time;
	pid_t child_pid;

	if (argc > 1)
	{
		ret = sscanf(argv[1], "%d", &proc_num);
		if (ret == 1)
		{
			printf("argv[1]: %d\n", proc_num);
		}
	}

	/* Start of experiment */
	gettimeofday(&start_tv, NULL);
	
	/* Create lot of child processes */
	count = 0;
	for(i = 0; i < proc_num; ++i)
	{
		child_pid = fork();
		if (child_pid == 0) {
			char *buff = (char*)malloc(BUFF_SIZE * sizeof(char));
			sleep(TIME_DELAY);
			free(buff);
			return EXIT_SUCCESS;
		} else if (child_pid == -1) {
			perror("fork()");
		} else {
			/* Count total number of created processes */
			count++;
		}
	}

	/* End of experiment */
	gettimeofday(&end_tv, NULL);

	diff_time = MICROSECONDS_IN_SECOND * (end_tv.tv_sec - start_tv.tv_sec) +
		(end_tv.tv_usec - start_tv.tv_usec);

	/* Maximum number of user processes can be changed using command:
	 *
	 * $ ulimit -u NEW_NUM
	 * 
	 */
	printf("%d of %d child processes created in %6.3f miliseconds\n",
		count, proc_num, ((float)diff_time)/1000.0 );

	sleep(2 * TIME_DELAY);

	/* code */
	return EXIT_SUCCESS;
}