So, if I follow correctly, we could maybe have one TLS pointer pointing to a
struct of pointers, one per each group of globals (one of this groups, would be
the set of variables used by getopt()), like:
struct task_globals_s
{
struct getopt_globals_s *getopt_globals;
/* ...others */
};
Then getopt globals would only be allocated once for each task, and only when
getopt() is called.
Something like that?
On Wed, Mar 24, 2021, at 11:24, Gregory Nutt wrote:
>
> > Of course, I would only call getopt() once. My question was if we use TLS,
> > would the memory use scale with the number of threads? Or would this memory
> > for getopt() only be allocated on getopt() calls?
>
> Yes and yes, but the memory use might be as small as a single pointer.
> Per task data would be better and exists now in the OS, but we would
> have to implement some internal OS api's that libc could use to access it.
>
> Another thing to consider is that the current per-task-data is protected
> and can only be accessed in supervisor mode. That is not a problem for
> the FLAT build but might add complication to the PROTECTED build (or at
> least more system call overhead).
>
> KERNEL build mode does not need per-task data at all. It would be
> better if the data could just be kept in globals for KERNEL build, just
> as with Linux.
>
>
>
