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Re: Any idea about what makes Emacs slow reading on pipes?
From: |
David Kastrup |
Subject: |
Re: Any idea about what makes Emacs slow reading on pipes? |
Date: |
19 May 2003 10:24:47 +0200 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.3.50 |
address@hidden (Kai Großjohann) writes:
> address@hidden (David Kastrup) writes:
>
> > Richard Stallman <address@hidden> writes:
> >
> >> We might change it so that, after stashing the stuff in a
> >> buffer, Emacs looks again if more data is available from the
> >> same process.
> >
> > More data will not be available from the same process, since the
> > process has not had any chance to get CPU time again for
> > generating more data. We are talking about a uniprocessor machine
> > here.
>
> I'm not familiar with the internals of Unix (-like) systems, but
> maybe it is possible to "look" in such a way that the scheduler has
> a chance to do its thing. For example, say that using select(2)
> causes the scheduler to run, then we might "look" using select(2).
The scheduler _has_ already made its decision, and the decision is to
have Emacs run rather than the output generating process.
There are various reasons: Emacs has been waiting on that pipe for a
longer time, so it is judged an "interactive program" and not a
calculating one. It gets an interactivity bonus and gets scheduled
immediately when available.
This interactivity bonus gets lower while busy processing continues.
That is the reason that after a while, a few larger packets make it
through.
> Hm. But this might make Emacs quite a bit slower. So maybe it is a
> good idea to only look twice if little data has been received. If a
> lot of data has been read, then we can just process that
> immediately.
The only way to yield is to actually and voluntarily call a delay.
This should only be done when there is reason to suspect it might be
worth a try, namely when we find ourselves repeatedly working on
small packets in fast succession. Emacs should just refuse to call a
process filter too fast twice in a row unless it has stuffed the
buffer sufficiently, and it should have a very fast path when it
decides not to run the process filter yet.
Perhaps a better scheme would be to use _blocking_ reads with the full
buffer length and a timeout instead when something is available. When
the blocking read fails, get just what is there.
--
David Kastrup, Kriemhildstr. 15, 44793 Bochum
- Re: Any idea about what makes Emacs slow reading on pipes?, (continued)
- Re: Any idea about what makes Emacs slow reading on pipes?, David Kastrup, 2003/05/16
- Re: Any idea about what makes Emacs slow reading on pipes?, Kim F. Storm, 2003/05/17
- Re: Any idea about what makes Emacs slow reading on pipes?, Stefan Monnier, 2003/05/17
- Re: Any idea about what makes Emacs slow reading on pipes?, David Kastrup, 2003/05/17
- Re: Any idea about what makes Emacs slow reading on pipes?, Stefan Monnier, 2003/05/17
- Re: Any idea about what makes Emacs slow reading on pipes?, Kai Großjohann, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, David Kastrup, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, Richard Stallman, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, David Kastrup, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, Kai Großjohann, 2003/05/19
- Re: Any idea about what makes Emacs slow reading on pipes?,
David Kastrup <=
- Re: Any idea about what makes Emacs slow reading on pipes?, Kai Großjohann, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, David Kastrup, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, Kai Großjohann, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, David Kastrup, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, Kai Großjohann, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, David Kastrup, 2003/05/18
- Re: Any idea about what makes Emacs slow reading on pipes?, Kai Großjohann, 2003/05/19
- Re: Any idea about what makes Emacs slow reading on pipes?, David Kastrup, 2003/05/19
- Re: Any idea about what makes Emacs slow reading on pipes?, Richard Stallman, 2003/05/18