Applied, thanks!
Sergey Bugaev, le sam. 15 avril 2023 19:17:18 +0300, a ecrit:
> It is common to have (some of) stdin, stdout and stderr point to the
> very same port. We were making the ctty RPCs that _hurd_port2fd () does
> for each one of them separately:
>
> 1. term_getctty ()
> 2. mach_port_deallocate ()
> 3. term_open_ctty ()
>
> Instead, let's detect this case and duplicate the ctty port we already
> have. This means we do 1 RPC instead of 3 (and create a single protid
> on the server side) if the file is our ctty, and no RPCs instead of 1
> if it's not. A clear win!
>
> Signed-off-by: Sergey Bugaev <buga...@gmail.com>
> ---
> hurd/dtable.c | 46 +++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 39 insertions(+), 7 deletions(-)
>
> diff --git a/hurd/dtable.c b/hurd/dtable.c
> index 5dd04131..41f4d7af 100644
> --- a/hurd/dtable.c
> +++ b/hurd/dtable.c
> @@ -60,18 +60,50 @@ init_dtable (void)
> _hurd_dtable[i] = NULL;
> else
> {
> + int copy;
> /* Allocate a new file descriptor structure. */
> struct hurd_fd *new = malloc (sizeof (struct hurd_fd));
> if (new == NULL)
> __libc_fatal ("hurd: Can't allocate initial file descriptors\n");
>
> - /* Initialize the port cells. */
> - _hurd_port_init (&new->port, MACH_PORT_NULL);
> - _hurd_port_init (&new->ctty, MACH_PORT_NULL);
> -
> - /* Install the port in the descriptor.
> - This sets up all the ctty magic. */
> - _hurd_port2fd (new, _hurd_init_dtable[i], 0);
> + /* See if this file descriptor is the same as a previous one we have
> + already installed. In this case, we can just copy over the same
> + ctty port without making any more RPCs. We only check the the
> + immediately preceding fd and fd 0 -- this should be enough to
> + handle the common cases while not requiring quadratic
> + complexity. */
> + if (i > 0 && _hurd_init_dtable[i] == _hurd_init_dtable[i - 1])
> + copy = i - 1;
> + else if (i > 0 && _hurd_init_dtable[i] == _hurd_init_dtable[0])
> + copy = 0;
> + else
> + copy = -1;
> +
> + if (copy < 0)
> + {
> + /* Initialize the port cells. */
> + _hurd_port_init (&new->port, MACH_PORT_NULL);
> + _hurd_port_init (&new->ctty, MACH_PORT_NULL);
> +
> + /* Install the port in the descriptor.
> + This sets up all the ctty magic. */
> + _hurd_port2fd (new, _hurd_init_dtable[i], 0);
> + }
> + else
> + {
> + /* Copy over ctty from the already set up file descriptor that
> + contains the same port. We can access the contents of the
> + cell without any locking since no one could have seen it
> + yet. */
> + mach_port_t ctty = _hurd_dtable[copy]->ctty.port;
> +
> + if (MACH_PORT_VALID (ctty))
> + __mach_port_mod_refs (__mach_task_self (), ctty,
> + MACH_PORT_RIGHT_SEND, +1);
> +
> + _hurd_port_init (&new->port, _hurd_init_dtable[i]);
> + _hurd_port_init (&new->ctty, ctty);
> + }
>
> _hurd_dtable[i] = new;
> }
> --
> 2.39.2
>
--
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.
