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From: Michael Albinus via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: Suhail Singh <suhailsingh247@gmail.com>, 73046@debbugs.gnu.org
Subject: bug#73046: 29.4; Emacs 100% CPU usage for several seconds when opening dired buffer over TRAMP
Date: Fri, 20 Sep 2024 11:54:28 +0200	[thread overview]
Message-ID: <87bk0ik5uz.fsf@gmx.de> (raw)
In-Reply-To: <86ed5mffbc.fsf@gnu.org> (Eli Zaretskii's message of "Sat, 14 Sep 2024 18:03:19 +0300")

Eli Zaretskii <eliz@gnu.org> writes:

Hi,

> If 3 surprised you, then the reason is simple: sit-for returns
> immediately if any input is available, so typing effectively disables
> the wait.  This could be countermanded by unconditional sleep, but
> AFAIU Michael is rethinking the whole issue, so we should wait for him
> to reach his conclusions.
>
> In any case, interrupting the wait when you type makes sense in
> general: it means Emacs is expected to respond sooner, which in most
> cases indeed means to stop waiting immediately.

I played with the different configurations to use sit-for. The test
scenario is simple and can be reproduced with any remote connection, be
it slow or fast:

--8<---------------cut here---------------start------------->8---
emacs -Q /ssh:remotehost:
M-! sleep 30
--8<---------------cut here---------------end--------------->8---

This starts a synchronous remote shell-command, and Tramp must wait for
the response in order to return the exit code (akways 9 in this
scenario). Observe the Emacs resource consumption by 'top' in another shell.

As a second test, I use the Tramp test suite in order to see whether
there is performance degradation. It is sufficient to run the test cases
tramp-test11-copy-file and tramp-test12-rename-file.

make -C test tramp-tests SELECTOR='"11\\|12"'

1. No sit-for call at all, as it has been the case when Suhail reported
the problem.

Emacs consumes 99% .. 100% CPU. The test suite reports

--8<---------------cut here---------------start------------->8---
   passed  1/2  tramp-test11-copy-file (1.645027 sec)
   passed  2/2  tramp-test12-rename-file (2.172439 sec)
--8<---------------cut here---------------end--------------->8---

2. Use (sit-for 0.005) in `tramp-wait-for-regexp', as done initially
with my patch.

Emacs consumes 42% .. 47% CPU. Good. However, the test suite reports

--8<---------------cut here---------------start------------->8---
   passed  1/2  tramp-test11-copy-file (5.311830 sec)
   passed  2/2  tramp-test12-rename-file (4.451581 sec)
--8<---------------cut here---------------end--------------->8---

This is a serious performance degradation, which isn't acceptable I
believe.

3. Use (sit-for 0.00005) in `tramp-wait-for-regexp', a much shorter timeout.

Emacs consumes 72% .. 74% CPU. Not ideal, but better than 100%. The test suite reports

--8<---------------cut here---------------start------------->8---
   passed  1/2  tramp-test11-copy-file (1.643277 sec)
   passed  2/2  tramp-test12-rename-file (1.800990 sec)
--8<---------------cut here---------------end--------------->8---

This is comparable to the initial values (there's always a small
difference).

4. Use (sit-for 0) in `tramp-wait-for-regexp'.

Emacs consumes 72% .. 74% CPU, the same as in 3. The test suite reports

--8<---------------cut here---------------start------------->8---
   passed  1/2  tramp-test11-copy-file (1.562353 sec)
   passed  2/2  tramp-test12-rename-file (1.626922 sec)
--8<---------------cut here---------------end--------------->8---

Seems to be the best compromise, I'm in the mood to apply.

Comments?

Best regards, Michael.





  parent reply	other threads:[~2024-09-20  9:54 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-09-05 14:24 bug#73046: 29.4; Emacs 100% CPU usage for several seconds when opening dired buffer over TRAMP Suhail Singh
2024-09-05 15:56 ` Eli Zaretskii
2024-09-05 21:04   ` Suhail Singh
2024-09-06  5:40     ` Eli Zaretskii
2024-09-06 13:23       ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-06 13:54         ` Eli Zaretskii
2024-09-06 14:09           ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-06 16:09             ` Eli Zaretskii
2024-09-06 17:47               ` Suhail Singh
2024-09-06 19:08                 ` Eli Zaretskii
2024-09-07  0:19                   ` Suhail Singh
2024-09-07  1:39                     ` Suhail Singh
2024-09-07  6:29                     ` Eli Zaretskii
2024-09-07  8:07                       ` Suhail Singh
2024-09-07 14:36                       ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-07 15:07                         ` Eli Zaretskii
2024-09-07 17:35                           ` Suhail Singh
2024-09-08 11:30                             ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-08 11:47                               ` Eli Zaretskii
2024-09-08 15:26                                 ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-08 15:41                                   ` Eli Zaretskii
2024-09-08 16:46                                     ` Suhail Singh
2024-09-08 17:53                                       ` Eli Zaretskii
2024-09-10  8:10                                     ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-11  1:05                                       ` Suhail Singh
2024-09-11 11:50                                         ` Eli Zaretskii
2024-09-11 16:29                                           ` Suhail Singh
2024-09-11 16:38                                             ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-11 17:25                                               ` Suhail Singh
2024-09-12 11:48                                                 ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-11 14:13                                         ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-11 15:56                                           ` Suhail Singh
2024-09-13 23:17                                       ` Suhail Singh
2024-09-14  6:24                                         ` Eli Zaretskii
2024-09-14 14:25                                           ` Suhail Singh
2024-09-14 14:41                                             ` Suhail Singh
2024-09-14 15:03                                             ` Eli Zaretskii
2024-09-14 22:36                                               ` Suhail Singh
2024-09-15  5:55                                                 ` Eli Zaretskii
2024-09-15 14:23                                                   ` Suhail Singh
2024-09-20  9:54                                               ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2024-09-20 10:47                                                 ` Eli Zaretskii
2024-09-20 14:18                                                 ` Suhail Singh
2024-09-20 15:35                                                   ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-20 15:42                                                     ` Suhail Singh
2024-09-21  8:30                                                     ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-21 14:06                                                       ` Suhail Singh
2024-09-14  7:07                                         ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-14 14:39                                           ` Suhail Singh
2024-09-20  8:48                                             ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-11 14:06                         ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-07 14:22                     ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-07 17:58                       ` Suhail Singh
2024-09-08 11:26                         ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-08 15:09                           ` Suhail Singh
2024-09-08 15:19                             ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-08 15:34                               ` Suhail Singh
2024-09-08 16:35                                 ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-11 16:19                                   ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-06 16:56             ` Suhail Singh
2024-09-06 16:01         ` Suhail Singh
2024-09-06 15:46       ` Suhail Singh
2024-09-06 15:52       ` Suhail Singh
     [not found] <87v7yz1sw8.fsf@rutgers.edu>
2024-09-13 15:47 ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-20 16:05   ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-20 17:11     ` Jake Nelson via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-09-21  6:59       ` Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors

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