Re: [RFD] Combined fork-exec syscall.

[Davide Libenzi <davidel@xmailserver.org>]

On Sun, 27 Apr 2003, Mark Grosberg wrote:

> Is there any interest in a single system call that will perform both a
> fork() and exec()? Could this save some extra work of doing a
> copy_mm(), copy_signals(), etc?
>
> I would think on large, multi-user systems that are spawning processes all
> day, this might improve performance if the shells on such a system were
> patched.
>
> Perhaps a system call like:
>
>    pid_t spawn(const char *p_path,
>                const char *argv[],
>                const char *envp[],
>                const int   filp[]);
>
> The filp array would allow file descriptors to be redirected. It could be
> terminated by a -1 and reference the file descriptors of the current
> process (this could also potentially save some dup() syscalls).
>
> If any of these parameters (exclusing p_path) are NULL, then the
> appropriate values are taken from the current process.
>
> I originally was thinking of a name of fexec() for such a syscall, but
> since there are already "f" variant syscalls (fchmod, fstat, ...) that an
> fexec() would make more sense about executing an already open file, so the
> name spawn() came to mind.
>
> I know almost all of my fork()-exec() code does almost the same thing. I
> guess vfork() was a potential solution, but this somehow seems cleaner
> (and still may be more efficient than having to issue two syscalls)...
> the downside is, of course, another syscall.

This is very much library stuff. I don't think that saving a couple of
system calls will give you an edge, expecially when we're talking of
spawning another process. Even if the process itself does nothing but
return. Ulrich might be eventually interested ...




- Davide