emacs -nw FILE incurs 2-second wait before displaying anything

emacs -nw FILE incurs 2-second wait before displaying anything

[Jim Meyering]

I've been annoyed with emacs -nw for a while (always building
from latest), and finally have investigated enough to report this.

When I run emacs -nw on an existing file, e.g.,

  echo xxx > foo
  emacs -nw foo

I see the normal start-up signs, then a two-second pause,
and then finally the contents of "foo" are displayed.

However, if I type anything before that two-minute pause,
I avoid the delay. Likewise, if I run emacs without -nw, this
two-second pause does not appear.

I traced it to the pselect call in wait_reading_process_output
that is in turn called from kbd_buffer_get_event.

It seems to me that it would be fine to wait for keyboard events
*after* the buffer has been displayed.  Not before.

Thanks for improving emacs!

Re: emacs -nw FILE incurs 2-second wait before displaying anything

[Eli Zaretskii]

> From: Jim Meyering <jim@meyering.net>
> Date: Mon, 26 May 2014 10:41:37 -0700
> 
> I've been annoyed with emacs -nw for a while (always building
> from latest), and finally have investigated enough to report this.
> 
> When I run emacs -nw on an existing file, e.g.,
> 
>   echo xxx > foo
>   emacs -nw foo
> 
> I see the normal start-up signs, then a two-second pause,
> and then finally the contents of "foo" are displayed.
> 
> However, if I type anything before that two-minute pause,
> I avoid the delay. Likewise, if I run emacs without -nw, this
> two-second pause does not appear.

Looks like the code in xterm.el which asks the terminal something and
waits for response.

Re: emacs -nw FILE incurs 2-second wait before displaying anything

[Stefan Monnier]

> However, if I type anything before that two-minute pause,
> I avoid the delay. Likewise, if I run emacs without -nw, this
> two-second pause does not appear.

Which terminal emulator are you running?
Can you show the output of `C-h l' right after this 2s pause?


        Stefan

Re: emacs -nw FILE incurs 2-second wait before displaying anything

[Jim Meyering]

On Mon, May 26, 2014 at 1:19 PM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> However, if I type anything before that two-minute pause,
>> I avoid the delay. Likewise, if I run emacs without -nw, this
>> two-second pause does not appear.
>
> Which terminal emulator are you running?
> Can you show the output of `C-h l' right after this 2s pause?

Good call.
This problem arises only with OS X's "Terminal" (2.3 (309)), but not
with aterm, xterm, or iTerm.  Here's the output of "C-h l":

ESC [ > 8 3 ; 4 0 0 0 3 ; 0 c C-h l

I had TERM set to xterm-256color.

Re: emacs -nw FILE incurs 2-second wait before displaying anything

[Stefan Monnier]

> This problem arises only with OS X's "Terminal" (2.3 (309)), but not
> with aterm, xterm, or iTerm.  Here's the output of "C-h l":

> ESC [ > 8 3 ; 4 0 0 0 3 ; 0 c C-h l

Hmmm... can you check with the Emacs pretest (24.3.91 or checked out
from `emacs-24')?  If you still see the problem there, please make it
a bug report so we can better track it.


        Stefan

Re: emacs -nw FILE incurs 2-second wait before displaying anything

[Jim Meyering]

On Mon, May 26, 2014 at 8:28 PM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> This problem arises only with OS X's "Terminal" (2.3 (309)), but not
>> with aterm, xterm, or iTerm.  Here's the output of "C-h l":
>
>> ESC [ > 8 3 ; 4 0 0 0 3 ; 0 c C-h l
>
> Hmmm... can you check with the Emacs pretest (24.3.91 or checked out
> from `emacs-24')?  If you still see the problem there, please make it
> a bug report so we can better track it.

I confirm that the 2-second delay still strikes when using a
just-bootstrapped-from-"emacs-24" binary and running
src/emacs -nw -Q FILE.  I see the same output as above for "C-h l".

As mentioned above, it appears to be terminal specific,
striking only when using OS X's "Terminal".
The delay arises before the contents of the FILE is first displayed,
and can be skipped if you know to type a key during that short
interval.  For some initial discussion, see this thread:

  https://lists.gnu.org/archive/html/emacs-devel/2014-05/msg00445.html