On Wed, Dec 15, 2010 at 1:50 PM, Enrico Granata <egranata@xxxxxxxx> wrote: > I believe his question actually sounds like: why does Linux need two system > calls to start running a new program? Wouldn't it be simpler to do this the > way Win32 does it: a CreateProcess() system call that actually loads a NEW > program in NEW process? fork() and exec() are not going to be replaced in our lifetime, so you are not going to be able to replace these system calls. Rather, you would be adding an extra system call which would cause all code using the system call to break backwards compatibly with any kernels which do not include this system call and break posix(not that that has stopped Linux in the past). This new system call would duplicate a lot of what fork is already doing. Here is a list from the posix spec on exec[1] which specifies all the elements inherited from the calling process and most of this is set up by fork so therefore it would need to be duplicated in the new system call. "The new process shall inherit at least the following attributes from the calling process image: [XSI] Nice value (see nice()) [XSI] semadj values (see semop()) Process ID Parent process ID Process group ID Session membership Real user ID Real group ID Supplementary group IDs Time left until an alarm clock signal (see alarm()) Current working directory Root directory File mode creation mask (see umask()) [XSI] File size limit (see ulimit()) Process signal mask (see sigprocmask()) Pending signal (see sigpending()) tms_utime, tms_stime, tms_cutime, and tms_cstime (see times()) [XSI] Resource limits [XSI] Controlling terminal [XSI] Interval timers" I believe most would say overhead is minimized via COW and therefore the speed benefit is not worth the issues as stated above. I believe that if the difference between fork/exec over one system call became large enough one may see a new system call created, but I do not see that being accepted upsteam any time soon(not that I have any say). fork/exec is a proven and well understood method for most programmers with c programming experience and while it may seem obscure at first it really isn't that confusing. Just my two cents, John [1]http://pubs.opengroup.org/onlinepubs/009695399/functions/environ.html -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
