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From: John Wiegley <johnw@gnu.org>
Subject: Re: request for review: Doing direct file I/O in Emacs Lisp
Date: Fri, 14 May 2004 14:43:59 -0700	[thread overview]
Message-ID: <m24qqivg4g.fsf@newartisans.com> (raw)
In-Reply-To: E1BOYsh-0008Tt-1R@fencepost.gnu.org

Richard Stallman <rms@gnu.org> writes:

> When eshell sees a redirect from a builtin, I think it would be most
> efficient to produce the output in a buffer and write it with
> write-region into the file.

Below are the results of comparing write-region to the file-handle
API.  This test used Eshell's builtin cat to write 21MB to another
file.

  ~74s  save-buffer (the current method)
  ~82s  file-handle-write
 ~250s  write-region [with call to `message' disabled]
 ~318s  write-region

It is interesting that write-region is by far the most inefficient,
and that my file-handle API is not the fastest method.  I therefore
retract my earlier proposal.

However, the real slowdown is with start-process, as others mentioned.
Here are the times for doing the same cat, but using the system's cat:

 ~952s  file-handle-write
  ...s  save-buffer (the current method)

In this case, save-buffer took so long that after 20 minutes Emacs
hung (for some other reason), and I didn't have sufficient patience to
run the test again.

> When it is a matter of a subprocess, what could be useful is a
> feature for start-process to specify files for additional
> descriptors.  That would be a completely different feature.

This would be very useful.

John

  parent reply	other threads:[~2004-05-14 21:43 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-05-10  5:59 request for review: Doing direct file I/O in Emacs Lisp John Wiegley
2004-05-10  6:52 ` Kim F. Storm
2004-05-10  8:27 ` David Kastrup
2004-05-10 14:21   ` Stefan Monnier
2004-05-10 15:59     ` David Kastrup
2004-05-10 16:36       ` Stefan Monnier
2004-05-10 17:00         ` David Kastrup
2004-05-10 17:22           ` Stefan Monnier
2004-05-11  9:23   ` John Wiegley
2004-05-11 10:22     ` David Kastrup
2004-05-10  9:38 ` Andreas Schwab
2004-05-10 11:29   ` Eli Zaretskii
2004-05-10 11:23     ` Andreas Schwab
2004-05-10 15:04       ` Eli Zaretskii
2004-05-10 14:19 ` Stefan Monnier
2004-05-10 17:46   ` Oliver Scholz
2004-05-10 18:21     ` Stefan Monnier
2004-05-10 22:40       ` Oliver Scholz
2004-05-11 12:22     ` Richard Stallman
2004-05-10 17:54 ` Richard Stallman
2004-05-11  9:20   ` John Wiegley
2004-05-12 19:41     ` Richard Stallman
2004-05-13  7:59       ` Kai Grossjohann
2004-05-14  9:21         ` Richard Stallman
2004-05-14 10:42           ` Kai Grossjohann
2004-05-15  8:53             ` Richard Stallman
2004-05-15 16:27               ` Kai Grossjohann
2004-05-16 13:20                 ` Richard Stallman
2004-05-14 21:43           ` John Wiegley [this message]
2004-05-15 18:33             ` Richard Stallman
2004-05-15 21:36               ` John Wiegley
2004-05-15 22:13                 ` David Kastrup
2004-05-16  6:41                   ` Eli Zaretskii
2004-05-16 17:46                     ` David Kastrup
2004-05-17 11:04                 ` Richard Stallman
2004-05-13 22:50       ` John Wiegley
2004-05-14 21:02         ` Richard Stallman

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