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: Tue, 02 Aug 2022 16:23:18 +0200 [thread overview]
Message-ID: <87o7x22089.fsf@gmx.de> (raw)
In-Reply-To: <CAG7Bpao05CAPG9ojqzFQtho2goAQ2Vbc2Ga=k-mTwW8+GfW65g@mail.gmail.com> (Paul Pogonyshev's message of "Mon, 1 Aug 2022 22:20:41 +0200")
Paul Pogonyshev <pogonyshev@gmail.com> writes:
Hi Paul,
> Understood, but I propose to adopt a different benchmark: number of
> remote commands. As soon as you are not in a LAN, even not when using
> a particularly slow network, this becomes an order or two of magnitude
> more important than everything else. E.g. with slightly slower
> commands or particularly inefficient Elisp you can make it 2-10 ms
> slower for everyone. But with unoptimized command flow (i.e. more
> remote commands) it can be 100-500 ms slower, though not for everyone,
> but people using this over non-LAN. I think in such cases extremes
> are more important than the average.
I agree, sending something over the wire is always slower than computing
clever caches locally.
>> And directories are also problematic for caches. As soon as something
>> changes there (creation or deletion of a file, for example), the cached
>> values of the directory must be flushed.
>
> Yeah, I suppose Tramp has no generic way to know that Magit issues
> reading commands. Can we devise a generic interface that would tell
> Tramp: "Commands within this block will not modify file system",
> e.g. with let-binding some variable?
They will modify the file system, although sometimes only the
timestamps.
Until now we have only something similar for synchronous
processes: process-file-side-effects. I have no idea whether package
authors are aware of this, and let-bind it to nil in case of. In the
magit sources, I haven't found this variable.
> In general, it feels like Tramp flushes its caches too often or maybe
> doesn't even cache certain things at all. I.e. it's not about those
> 10 seconds (following your advice I have even increased that). It's
> that while serving one user-level command here (i.e. within 3 seconds
> at most), it can issue the same remote command several times, thus
> not reusing previous results.
Well, that's right. If, for example, the file modes are changed, Tramp
flushes all caches for that file, although some of them
("file-exists-p", "file-directory-p" etc) aren't affected.
> E.g. in the traces you have attached this can be seen. The following
> two commands repeat twice:
I haven't investigated this special case yet, but last days I'm working
on exact this problem. Flushing caches shouldn't be a sledge hammer, but
fine grained, selecting the needed properties to be flushed. Let's see
where we land.
> Paul
Best regards, Michael.
next prev parent reply other threads:[~2022-08-02 14:23 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
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 [this message]
2022-07-04 10:33 ` Michael Albinus
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87o7x22089.fsf@gmx.de \
--to=michael.albinus@gmx.de \
--cc=56342@debbugs.gnu.org \
--cc=pogonyshev@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/emacs.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).