bug#24113: 25.1.50; auto-revert-check-vc-info causes delayed screen refreshs

bug#24113: 25.1.50; auto-revert-check-vc-info causes delayed screen refreshs

[Torsten Bronger]

If auto-revert-check-vc-info is non-nil and some buffers contain
version-controlled files, the screen refresh is often delayed.  For
example, I press "g" in Gnus to get new news, they are indeed fetched,
but the screen does not change at first.  After a couple of seconds, the
screen is updated and I see the new numbers of messages.

This is *much* more visible if Emacs is used through an X tunnel (what I
often do).  But it also happens locally.

Note that this definitely is not caused by a slow NNTP connection.  I
observe the same thing when pressing RET in a Gnus mail folder summary
buffer, when everything is fetched locally.  I observe the same thing in
many other situations outside Gnus, sometimes even when I simply insert
a character: It does appear only after a couple of seconds.

Every time this happens, I can immediately proceed after hitting any
key.  I frequently use the cursor keys for that because they don't
actually do anything.

It also causes massive delays during Emacs startup if many buffers need
to be restored from the desktop file.  Therefore, I usually press
left-right-left-right-left-right... during startup to accelerate it.

I observe this for years now in SVN/Bazaar/Git Emacs, but not before
last week I finally found out that auto-revert-check-vc-info is the
trigger.


In GNU Emacs 25.1.50.10 (x86_64-pc-linux-gnu)
 of 2016-07-08 built on wolowitz
Repository revision: 56c8551219ecace0157ce813733adf8eecb38c32
Windowing system distributor 'The X.Org Foundation', version 11.0.11803000
System Description:	Ubuntu 16.04.1 LTS

Recent messages:
Enter a change comment.  Type C-c C-c when done
Checking in /home/bronger/src/lensfun/tools/calibration_webserver/calibration/views.py...done
remote: <Repository /git/p/lensfun/code.git> refresh queued.        
To ssh://bronger@git.code.sf.net/p/lensfun/code
   85a20ea..528e611  master -> master
To git@github.com:lensfun/lensfun.git
   85a20ea..528e611  master -> master
Auto-saving...
Mark set
Making completion list...

Configured using:
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Important settings:
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/home/bronger/.emacs.d/lisp/yasnippet/snippets/fundamental-mode/.yas-setup hides /home/bronger/.emacs.d/lisp/yasnippet/yasmate/snippets/objc-mode/.yas-setup
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/home/bronger/.emacs.d/lisp/yasnippet/snippets/fundamental-mode/.yas-setup hides /home/bronger/.emacs.d/lisp/yasnippet/yasmate/snippets/ruby-mode/.yas-setup
/home/bronger/.emacs.d/lisp/yasnippet/yasmate/snippets/html-mode/.yasmate-extra-substitutions hides /home/bronger/.emacs.d/lisp/yasnippet/yasmate/snippets/ruby-mode/.yasmate-extra-substitutions

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-- 
Torsten Bronger    Jabber ID: torsten.bronger@jabber.rwth-aachen.de

bug#24113: 25.1.50; auto-revert-check-vc-info causes delayed screen refreshs

[Lars Ingebrigtsen]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> If auto-revert-check-vc-info is non-nil and some buffers contain
> version-controlled files, the screen refresh is often delayed.  For
> example, I press "g" in Gnus to get new news, they are indeed fetched,
> but the screen does not change at first.  After a couple of seconds, the
> screen is updated and I see the new numbers of messages.

I've tried running with that variable set to t for a while now, and I
haven't seen any strange pauses after hitting `g' in the *Group* buffer.

Are you still seeing this problem in more recent Emacs version?  If so,
could you try to create a simpler test case for reproducing the problem?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#24113: 25.1.50; auto-revert-check-vc-info causes delayed screen refreshs

[Torsten Bronger]

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Hallöchen!

Lars Ingebrigtsen schreibt:

> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>
>> If auto-revert-check-vc-info is non-nil and some buffers contain
>> version-controlled files, the screen refresh is often delayed.
>> For example, I press "g" in Gnus to get new news, they are indeed
>> fetched, but the screen does not change at first.  After a couple
>> of seconds, the screen is updated and I see the new numbers of
>> messages.
>
> I've tried running with that variable set to t for a while now,
> and I haven't seen any strange pauses after hitting `g' in the
> *Group* buffer.
>
> Are you still seeing this problem in more recent Emacs version?

Not with Gnus and hitting "g".  But still on start-up.

> If so, could you try to create a simpler test case for reproducing
> the problem?

Not simpler, but clearer and hopefully more reliable.

1. Make your Emacs use the following simple .emacs configuration
   file:

       (custom-set-variables
        '(auto-revert-check-vc-info t)
        '(desktop-save-mode t)
       )

   Remove your .emacs.desktop for a fresh start.

2. Make a new directory and create many files in it, e.g. by saying

       mkdir test; cd test; for a in `seq 100`; do touch $a; done

3. Start Emacs and open all of these files, e.g. by using dired-x
   and the keybinding "F".  (Obviously, you have to expand your
   .emacs for this a bit.)  Then, close Emacs let Emacs write your
   buffer status to the desktop file.

4. Open Emacs again.  It will start quickly.  Close it.

5. Say in the directory with the many files:

       git init

6. Open Emacs again.  It will start very slowly.  Close it.

7. Open Emacs again.  This time, press any key during start-up.  It
   will start quickly again.

What I expect is that Emacs always starts quickly, even without
pressing a key.  I can safely say that the delay is VC-related but I
don't know how to proceed to find out at which operation Emacs
hangs.

Regards,
Torsten.

-- 
Torsten Bronger

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bug#24113: 25.1.50; auto-revert-check-vc-info causes delayed screen refreshs

[Lars Ingebrigtsen]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> 1. Make your Emacs use the following simple .emacs configuration
>    file:
>
>        (custom-set-variables
>         '(auto-revert-check-vc-info t)
>         '(desktop-save-mode t)
>        )
>
>    Remove your .emacs.desktop for a fresh start.
>
> 2. Make a new directory and create many files in it, e.g. by saying
>
>        mkdir test; cd test; for a in `seq 100`; do touch $a; done
>
> 3. Start Emacs and open all of these files, e.g. by using dired-x
>    and the keybinding "F".  (Obviously, you have to expand your
>    .emacs for this a bit.)  Then, close Emacs let Emacs write your
>    buffer status to the desktop file.
>
> 4. Open Emacs again.  It will start quickly.  Close it.

I had to do a `M-x desktop-read' to get my "emacs -Q" to open the
desktop file, but it did start quickly.

> 5. Say in the directory with the many files:
>
>        git init
>
> 6. Open Emacs again.  It will start very slowly.  Close it.
>
> 7. Open Emacs again.  This time, press any key during start-up.  It
>    will start quickly again.

I didn't see any differences in speed here.  Are there any missing steps
to the recipe?  (I'm testing with "emacs -Q" in Emacs 28 and 27.2).

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#24113: 25.1.50; auto-revert-check-vc-info causes delayed screen refreshs

[Torsten Bronger]

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Hallöchen!

Lars Ingebrigtsen writes:

> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>
> [...]
>>
>> 7. Open Emacs again.  This time, press any key during start-up.  It
>>    will start quickly again.
>
> I didn't see any differences in speed here.  Are there any missing
> steps to the recipe?  (I'm testing with "emacs -Q" in Emacs 28 and
> 27.2).

Now, I cannot reproduce it myself any more.  Not even with an older
Emacs.  Something in the environment has changed, apparently.

I suggest to close it.

Regards,
Torsten.

-- 
Torsten Bronger

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bug#24113: 25.1.50; auto-revert-check-vc-info causes delayed screen refreshs

[Lars Ingebrigtsen]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> Now, I cannot reproduce it myself any more.  Not even with an older
> Emacs.  Something in the environment has changed, apparently.
>
> I suggest to close it.

Thanks for checking; I'm closing the bug report, then.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no