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bug#35418: [PATCH] Don't poll auto-revert files that use notification
From: |
Mattias Engdegård |
Subject: |
bug#35418: [PATCH] Don't poll auto-revert files that use notification |
Date: |
Mon, 29 Apr 2019 13:54:48 +0200 |
29 apr. 2019 kl. 09.19 skrev Michael Albinus <michael.albinus@gmx.de>:
>
> By design, in filenotify.el, we want see only events which are related
> to the file *name*. If you want to be notified for both buffers, you
> need to watch both file (names).
Well yes, but you want a change to the file to be reported for both buffers,
even if they watch different names, right?
Otherwise, it wouldn't make sense at all. If someone is watching a file, surely
it is because changes to the contents of that file are of interest? Why would
the name employed to carry out the changes matter?
I'm quite sure there is a simple misunderstanding here; probably my fault. And
again, I don't think it matters much in practice since users are unlikely to
have buffers for different hard links to the same file. Let's not waste too
much time on this.
>> However, with the kqueue back-end, file-notify watches do trigger for
>> both, as expected.
>
> Hmm, this is inconsistent. Worth a buig report?
Not really, because (a) multiple hard links are rare, (b) even more rare in
Emacs, and (c) inotify isn't used that way by auto-revert (the directory is
watched, not the files).
> It was a design decision, that filenotify.el implements directory
> watching. Since kqueue does not support this, it must be emulated, somehow.
Well, auto-revert only uses filenotify.el for watching changes to files (that
is, the data corresponding to the names). How filenotify does that isn't very
important. I suppose watching directories when possible has the advantages:
+ fewer (kernel-level) descriptors used if there are multiple files of interest
in the same directory
+ notification about re-created previously removed files
with at least one disadvantage:
- changes to files not of interest have to be considered and rejected, spending
more CPU and power. This can be non-trivial; consider looking at a single
non-changing file in a very busy directory with files being added and removed
all the time.
For kqueue and w32notify (and FSEvent) there isn't much choice.
>> What other reasons are you thinking about?
>
> The reasons you have already quoted somewhere else: sometimes, file
> notification is not applicable; there are not enough descriptors left; a
> file might have been deleted; a file notification process has been
> killed silently; you name it ...
Thank you. Most of those cases should not cause any trouble -- except
unreliable file notification processes, but since `auto-revert-remote-files'
defaults to nil, it didn't look like a serious problem.
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, (continued)
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Eli Zaretskii, 2019/04/29
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Mattias Engdegård, 2019/04/30
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Michael Albinus, 2019/04/30
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Mattias Engdegård, 2019/04/30
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Michael Albinus, 2019/04/30
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Eli Zaretskii, 2019/04/29
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Mattias Engdegård, 2019/04/29
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Michael Albinus, 2019/04/29
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Mattias Engdegård, 2019/04/30
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Michael Albinus, 2019/04/29
- bug#35418: [PATCH] Don't poll auto-revert files that use notification,
Mattias Engdegård <=
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Michael Albinus, 2019/04/29
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Mattias Engdegård, 2019/04/29
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Michael Albinus, 2019/04/29
- bug#35418: [PATCH] Don't poll auto-revert files that use notification, Eli Zaretskii, 2019/04/30
bug#35418: [PATCH] Don't poll auto-revert files that use notification, Michael Albinus, 2019/04/24
bug#35418: [PATCH] Don't poll auto-revert files that use notification, Zhang Haijun, 2019/04/29