From: Thierry Volpiatto <thierry.volpiatto@gmail.com>
To: emacs-devel@gnu.org
Subject: Re: tramp ControlMaster options
Date: Tue, 21 Jul 2015 07:09:39 +0200 [thread overview]
Message-ID: <87mvyqjdv0.fsf@gmail.com> (raw)
In-Reply-To: mojmcu$uma$1@ger.gmane.org
Yuri D'Elia <wavexx@thregr.org> writes:
> On 20/07/15 20:43, Michael Albinus wrote:
>> Likely you mean `tramp-ssh-controlmaster-options'. This is a variable,
>> and it will be computed only when it is needed. No Tramp ssh connection,
>> no probe of ssh for this.
>
> I hope I understand how defcustom works(?).
> In emacs 24.5.1, I see this at line 310 of tramp.el:
>
> (defcustom tramp-ssh-controlmaster-options
> ...
>
> whose standard value is computed by calling ssh a few times.
> I don't know what the ;;;###tramp-autoload cookie does though, but no
> miracles I assume?
>
> Just to confirm, this is the output of "strace -f -e trace=process"
> after a (require 'tramp):
>
> [pid 2189] vfork(Process 2255 attached
> <unfinished ...>
> [pid 2255] execve("/usr/bin/ssh", ["/usr/bin/ssh", "-o",
> "ControlMaster"], [/* 73 vars */] <unfinished ...>
> [pid 2189] <... vfork resumed> ) = 2255
> [pid 2255] <... execve resumed> ) = 0
> [pid 2255] arch_prctl(ARCH_SET_FS, 0x7fcdde4cd800) = 0
> ...
So IIUC tramp is calling ssh at load time when evaling its defcustom ?!!
>>> Any reason why we cannot use `ssh -o BatchMode=yes [various flags]
>>> 0.0.0.0' instead of using a domain name? This would greatly reduce the
>>> issue.
>>
>> The function (!) `tramp-ssh-controlmaster-options' uses "localhost" for
>> test. This shall avoid DNS requests.
>
> Still connects to a valid host, which might have a daemon running (in
> fact, I have one on localhost for debugging).
>
> If there's no reason to connect to something, call 0.0.0.0.
Isn't it possible to setup the default value of
`tramp-ssh-controlmaster-options' only when tramp is involved (i.e at
first connection) instead of evaling this at load time ?
If tramp hang forever like it is the case actually user will know why
emacs is hanging.
> I love that tramp detects ControlMaster support in ssh, but calling
> external processes on load, if really needed, should /really/ be quick.
IMHO this should not happen at load time.
Thanks.
--
Thierry
Get my Gnupg key:
gpg --keyserver pgp.mit.edu --recv-keys 59F29997
next prev parent reply other threads:[~2015-07-21 5:09 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-17 11:11 package.el: what does package "Checking ... " actually do? Yuri D'Elia
2015-07-17 12:36 ` Artur Malabarba
2015-07-17 13:19 ` Artur Malabarba
2015-07-18 11:22 ` Yuri D'Elia
2015-07-18 12:44 ` tramp ControlMaster options (was: Re: package.el: what does package "Checking ... " actually do?) Yuri D'Elia
[not found] ` <55AA4AF3.2030901@thregr.org>
2015-07-20 5:38 ` tramp ControlMaster options Michael Albinus
2015-07-20 6:21 ` Thierry Volpiatto
2015-07-20 8:07 ` Yuri D'Elia
2015-07-20 18:43 ` Michael Albinus
2015-07-20 20:41 ` Yuri D'Elia
2015-07-21 5:09 ` Thierry Volpiatto [this message]
2015-07-21 5:53 ` Michael Albinus
2015-07-21 7:22 ` Thierry Volpiatto
2015-07-21 10:59 ` Yuri D'Elia
2015-07-22 5:58 ` Michael Albinus
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