From: Stephen Leake <stephen_leake@stephe-leake.org>
To: 18626@debbugs.gnu.org
Subject: bug#18626: 24.3.94; communication with subprocess is slow
Date: Sat, 04 Oct 2014 03:11:26 -0500 [thread overview]
Message-ID: <85d2a8dzkh.fsf@stephe-leake.org> (raw)
In-Reply-To: <85wq8ge3gr.fsf@stephe-leake.org>
As Eli suggested, I tried changing the pipe buffer size in w32.c pipe2,
and the delay in process.c send_process, call to
wait_reading_process_output.
The pipe buffer size should affect reading from the subprocess, but it
doesn't change the timing significantly:
(pipe-torture-read "/Projects/emacs/emacs-24.3.94/src/xdisp.c")
size time
------------------------
0 (uses OS default) 11.965184
9192 12.012684
80000 12.018934
The send_process time delay is the cause of the slowdown in write:
(find-file "xdisp.c")
(pipe-torture "debug.exe" "4096")
delay time
------------------------
20 * 1000 * 1000 4.450068
10 * 1000 * 1000 2.443788
0 * 1000 * 1000 hangs until C-g
xdisp.c has 974233 bytes; with a subprocess read buffer of 4096 and a
delay of 0.020 seconds, that gives a send time of (* 0.020 (/ 974233
4096)) = 4.74, which is close to what we see above.
One way around the write delay is to use a large enough read buffer in
the subprocess. In my current real application, this is easy and also
gives other benefits.
I'm not clear why Emacs hangs with a delay of 0. The subprocess should
be running on a separate CPU core, so even if the Emacs process is in a
busy wait loop, the subprocess should read input.
--
-- Stephe
next prev parent reply other threads:[~2014-10-04 8:11 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 [this message]
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
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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