From: Paul Pogonyshev <pogonyshev@gmail.com>
To: Michael Albinus <michael.albinus@gmx.de>
Cc: 56342@debbugs.gnu.org
Subject: bug#56342: TRAMP (sh) issues way too many commands, thus being very slow over high-ping networks
Date: Mon, 4 Jul 2022 16:42:26 +0200 [thread overview]
Message-ID: <CAG7BpapO9Rnppfxgnng8S-kG__TB=XdAXTpkzrEuEVu8fC-A1w@mail.gmail.com> (raw)
In-Reply-To: <87sfnhazvy.fsf@gmx.de>
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> It returns "'/tmp/c' -> '/tmp/b'". However, we need "/tmp/a". So we must
> still use "readlink --canonicalize".
According to a quick search, it is possible to merge output of several
shell commands together. This seems to work even with dumb `sh', it's not a
Bash extension:
$ sh -c '{ stat xxx && readlink xxx; }'
I guess TRAMP could just sth. similar, as I understand it doesn't have to
be strictly one executable call, just one command given to the remote shell.
> Tramps communication with the remote host is like a REPL engine. It
> sends shell commands to the remote hosts, reads the result, and waits
> for the shell prompt. If it doesn't wait for the final shell prompt, it
> is likely that the result or the shell prompt will be seen when reading
> the output of the next command. This confuses. So no, I don't see a
> chance to implement this kind of "asynchronity".
I see parameter `nooutput' to `tramp-send-command'. Couldn't that be used?
Even if not, I could imagine sth. like this:
(defvar pending-commands nil)
(defvar reading-output nil)
(defun send-command (x output-inessential)
(if output-inessential
(setf pending-commands (nconc pending-commands (list x)))
(while reading-output ; make sure the connection is free for the
next essential command
(read-next-output-chunk)
(when (and (not reading-output) pending-commands)
(do-send-command (pop pending-commands))))
(do-send-command x)
(read-output-now)))
(defun do-send-command (x)
(really-do-send-it x)
(setf reading-output t))
(defun read-output-now ()
(while reading-output
(read-next-output-chunk))
(extract-received-output-from-process-buffer))
(defun emacs-idling () ; hooked up using `run-with-idle-timer' or
something like that
(cond (reading-output
(read-next-output-chunk))
(pending-commands
(do-send-command (pop pending-commands)))))
(defun read-next-output-chunk ()
(when reading-output
(do-read-output-chunk) ; this should be non-blocking
(when (end-of-command-output)
(setf reading-output nil))))
Paul
On Mon, 4 Jul 2022 at 13:19, Michael Albinus <michael.albinus@gmx.de> wrote:
> Paul Pogonyshev <pogonyshev@gmail.com> writes:
>
> Hi Paul,
>
> >> Doing it asynchronously would require a second connection to the remote
> >> host. Performance would rather degrade.
> >
> > Maybe not really asynchronously, just let it return early, not waiting
> > for the result? I'm not sure how TRAMP receives responses, but can it
> > just keep executing commands sequentially, as now, but give control
> > back to the caller in case of commands where the result doesn't really
> > matter (cleanup, e.g. deleting a temporary file). Of course, this
> > means that if an "important" command is issued right away, it has to
> > wait for the response to the previous inessential command. But when
> > such an inessential command is the last in a batch, this waiting would
> > be effectively merged with Emacs' idling in the normal UI command
> > loop, making things more responsive for the user.
>
> Tramps communication with the remote host is like a REPL engine. It
> sends shell commands to the remote hosts, reads the result, and waits
> for the shell prompt. If it doesn't wait for the final shell prompt, it
> is likely that the result or the shell prompt will be seen when reading
> the output of the next command. This confuses. So no, I don't see a
> chance to implement this kind of "asynchronity".
>
> > Paul
>
> Best regards, Michael.
>
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next prev parent reply other threads:[~2022-07-04 14:42 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-01 17:14 bug#56342: TRAMP (sh) issues way too many commands, thus being very slow over high-ping networks Paul Pogonyshev
2022-07-02 15:58 ` Michael Albinus
2022-07-02 18:14 ` Paul Pogonyshev
2022-07-03 12:16 ` Michael Albinus
2022-07-03 14:00 ` Paul Pogonyshev
2022-07-03 18:47 ` Michael Albinus
2022-07-03 19:52 ` Paul Pogonyshev
2022-07-04 11:19 ` Michael Albinus
2022-07-04 14:42 ` Paul Pogonyshev [this message]
2022-07-04 16:30 ` Michael Albinus
2022-07-26 8:00 ` Paul Pogonyshev
2022-07-26 14:18 ` Michael Albinus
2022-07-26 16:17 ` Paul Pogonyshev
2022-07-26 17:51 ` Michael Albinus
2022-08-01 20:20 ` Paul Pogonyshev
2022-08-02 14:23 ` Michael Albinus
2022-07-04 10:33 ` Michael Albinus
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