From: Stephen Leake <stephen_leake@stephe-leake.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 18626@debbugs.gnu.org
Subject: bug#18626: 24.3.94; communication with subprocess is slow
Date: Wed, 08 Oct 2014 08:29:59 -0500 [thread overview]
Message-ID: <85ppe2vgdk.fsf@stephe-leake.org> (raw)
In-Reply-To: <85r3ymcr0u.fsf@stephe-leake.org> (Stephen Leake's message of "Sun, 05 Oct 2014 13:25:53 -0500")
Stephen Leake <stephen_leake@stephe-leake.org> writes:
> It is still a problem on Windows; 12 seconds to read a megabyte is
> unacceptably slow for my real application.
The cause for this is the Sleep in _sys_read_ahead in w32.c. This is
called from reader_thread after the wait for a single char read
succeeds. The default wait is 50 ms, set by the elisp variable
w32-pipe-read-delay. Setting that to 0 gives:
(pipe-torture-read "/Projects/emacs/emacs-24.3.94/src/xdisp.c")
0.180000, 0.095000
only a factor of 2 slower than command-line cat.
w32-pipe-read-delay is a global variable. The comment in _sys_read_ahead
says there are problems with subprocess interaction when setting this to
0 on some systems. If that is still true, we may need to change this to
a per-subprocess setting.
In my real application, let-binding w32-pipe-read-delay for a short time
is possible, and a reasonable workaround.
--
-- Stephe
next prev parent reply other threads:[~2014-10-08 13:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-04 6:47 bug#18626: 24.3.94; communication with subprocess is slow stephen_leake
2014-10-04 8:07 ` Eli Zaretskii
2014-10-05 13:20 ` Stephen Leake
2014-10-05 13:41 ` Stephen Leake
2014-10-05 14:43 ` Eli Zaretskii
2014-10-05 18:19 ` Stephen Leake
2014-10-04 8:11 ` Stephen Leake
2014-10-04 8:32 ` Eli Zaretskii
2014-10-04 22:29 ` Stefan Monnier
2014-10-05 2:46 ` Eli Zaretskii
2014-10-05 13:34 ` Stephen Leake
2014-10-05 14:40 ` Eli Zaretskii
2014-10-05 18:25 ` Stephen Leake
2014-10-05 19:04 ` Eli Zaretskii
2014-10-08 13:29 ` Stephen Leake [this message]
2014-10-08 13:53 ` Eli Zaretskii
2014-10-10 8:07 ` Stephen Leake
2014-10-10 9:13 ` Eli Zaretskii
2014-10-10 8:47 ` Stephen Leake
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