From: Michael Albinus <michael.albinus@gmx.de>
To: Paul Pogonyshev <pogonyshev@gmail.com>
Cc: 56342@debbugs.gnu.org
Subject: bug#56342: TRAMP (sh) issues way too many commands, thus being very slow over high-ping networks
Date: Sun, 03 Jul 2022 14:16:24 +0200 [thread overview]
Message-ID: <87v8sefl2f.fsf@gmx.de> (raw)
In-Reply-To: <CAG7BpapA6=kvxNX8siHSEyVHytRdYVA_S2W=gwHJvN2LjNkt2A@mail.gmail.com> (Paul Pogonyshev's message of "Sat, 2 Jul 2022 20:14:35 +0200")
Paul Pogonyshev <pogonyshev@gmail.com> writes:
Hi Paul,
> Some more thoughts. Why does it even need `echo are you awake'? It's a
> network connection, it can still fail even if it worked fine 1 ms
> before when you checked. So, why not just let the first command fail
> if the connection is dead and restart the connection if it fails in
> such a way as to suspect that it is dead (i.e. no output)? Maybe limit
> this to read commands.
This is a sanity check. It avoids to hang in a blocked connection,
because this special command is surrounded by a timeout of 10 sec. Other
commands w/o this protection could hang forever. See also the comment in
tramp-maybe-open-connection.
> A way to let higher-level code avoid certain `file-exists-p' calls:
> add a dynamic variable that tells TRAMP to skip certain commands if
> the result is not available from a cache. Something similar to
> `process-file-side-effects'. Calling code could then do sth. like
> this:
>
> (when (let ((tramp-may-skip-if-not-cached `((file-exists-p unknown
> ,file))))
> (file-exists-p file)) ; TRAMP will return t or nil if it
> knows or 'unknown if not cached; for local files there is no effect
> ...)
>
> Suggested semantics: list of (FUNCTION INSTANT-RESULT-IF-NOT-CACHED
> ARGUMENT...). Any element of the list with unknown function name etc.
> would be simply ignored.
>
> Code that doesn't let-bind this variable will behave as before. Code
> that cares can be optimized.
If a caller can live w/o a valid result of file-exists-p, it shouldn't
call it. Everything else is too sophisticated and good for trouble, I believe.
In general, packages shall not care what's the implementation of a given
function like file-exists-p. If they care, they could still use
file-remote-p in order to distinguish.
> Paul
Best regards, Michael.
next prev parent reply other threads:[~2022-07-03 12:16 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 [this message]
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
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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