[Blue forest-free software] - Linux programming process with the use of multi-threaded Why? Programming Problems 1-C + +

Linux C and C + + programming process threads

Programming engaged Linux/UNIX years, has been using the fork in the process of writing more procedures. When friends ask why Linux rarely use when programming thread found myself really need to study this problem. Manual check fork man has been suggested by the following :
Fork creates a child process that differs from the parent process only in its PID and PPID. and in the fact that resource utilizations are set to 0. File locks and pending signals are not inherited.
Under Linux, fork is implemented using copy-on-write pages. so the only penalty incurred by fork is the time and memory required to duplicate the parent 's page tables. and to create a unique task structure for the child.
The only thing to do is fork duplicating page (page tables) and the creation of task structure. In addition, the process appears only difference is that his father PID and PPID of 0 and resource consumption.
However, if one examines the LinuxThreads PTHREAD_CREATE (3) is the creation of a thread only, and no mention of the relevant details.
Actual situation? I have prepared the following two codes :
*/ /*forktest.c As follows :
#include "Stdlib.h>
#include "Sys/types.h>
#include "Unistd.h>
#include "Unistd.h>
#include "Stdio.h>

Int main (int argc, char ** argv)
{
Pid_t pid;
Char * mem;
If (argc "4) {printf (" \r\nusage : %s time1 time2 memory-size\n "argv[0]); Return 1;}
Mem = (char *) malloc (atoi (argv[3])); LEAVES OF 13 SPECIES OF LAURACEAE tests the memory occupied by deliberately imported 1G or more memory demand */
Pid = fork ();
If (pid ====== 0) (
Sleep (atoi (argv[1]));
Exit (0);
}
Sleep (atoi (argv[2]));
Return 0
}
LEAVES OF 13 SPECIES OF LAURACEAE this translated into executable code procedures a-fork*/

*/ /*pthread_create.c As follows :
#include "Unistd.h>
#include "Pthread.h>
Void * start_routine (void * a)
{
Sleep (30);
}

Int main (int argc, char ** argv)
{
Int ret;
Pthread_t pth;
Ret = pthread_create (&pth, NULL, start_routine, NULL);
Sleep (35);
Return 0
}
LEAVES OF 13 SPECIES OF LAURACEAE this translated into executable code procedures a-thread*/

Then these two operating procedures, and the top order ps order observed that the surface has been as follows :
1, are two CPUs share %CPU 0
2, the two share a memory a-thread %MEM:a-fork 0.5 and 0.6
3, after the two procedures could see the two processes ps (process a-fork two a-thread process has two)

See the depth understanding of the phenomenon :
3 is due to the above results LinuxThreads threads and processes is used in the "one-to-one" model, the dispatch to the core, and in the realization of a user-level threads, including the signal processing and control mechanisms.
These results are in the process one should sleep, it is understandable that the bar did not occupy the CPU.
But why be the first two findings that the memory a-thread share even higher than a-fork? Although the symptoms can tell me why you like the process of programming and the use of thread programming, however true in the end Why? I have this to the test in the end not? (I also use their own PC in the test ah), it must carefully study kernel source code ah know.
Information available : Because of the unique advantages of Linux, the Linux process is more efficient, and lightweight, so the preferred Linux programming process.