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: Sun, 05 Oct 2014 13:19:18 -0500 [thread overview]
Message-ID: <85vbnycrbt.fsf@stephe-leake.org> (raw)
In-Reply-To: <831tqmo9v4.fsf@gnu.org> (Eli Zaretskii's message of "Sun, 05 Oct 2014 17:43:27 +0300")
Eli Zaretskii <eliz@gnu.org> writes:
>> From: Stephen Leake <stephen_leake@stephe-leake.org>
>> Cc: 18626@debbugs.gnu.org
>> Date: Sun, 05 Oct 2014 08:41:08 -0500
>>
>> (find-file "xdisp.c")
>> (pipe-torture
>> "/home/Projects/org.emacs.ada-mode.stephe-1/build/wisi/debug_counted"
>> "4096" "974230")
>>
>> 0.344027
>>
>> This is comparable to the time on Windows with a large buffer in the
>> subprocess. So apparently it is not using the same delay in
>> send_process. Or the IO system is providing a large buffer.
>
> Evidently, subprocess I/O is more efficient on GNU/Linux than it is on
> Windows. Perhaps this is related to the fact that by default
> GNU/Linux uses PTYs for that, not pipes. Did you try your experiments
> with process-connection-type bound to nil?
On Debian:
(setq process-connection-type nil)
(pipe-torture-read "/home/Projects/emacs/emacs-24.3.94/src/xdisp.c")
0.074980
no signficant change
(find-file "xdisp.c")
(pipe-torture
"/home/Projects/org.emacs.ada-mode.stephe-1/build/wisi/debug_counted"
"4096" "974230")
0.294485, 0.304046, 0.343767
(pipe-torture
"/home/Projects/org.emacs.ada-mode.stephe-1/build/wisi/debug_counted"
"40000" "974230")
0.341241, 0.342165
Slower than pty, but much faster than Windows, and still independent of
subprocess read buffer size.
(setq process-connection-type nil) also eliminates the line-by-line
read; for a buffer size of 4096, Read returns 4096 until the end of the
text. For a buffer size of 40000, Read returns 40000 or 25536 until the
end of the text. (+ 40000 25536) = 65536, which makes sense for the
default pipe buffer size.
Given a send_process delay of 0.020 on EWOULD_BLOCK, and a buffer size
of 65536, the expected write time is (* 0.020 (/ 974230 65536)) = 0.28,
comparable to what we see.
Apparently pty's do the line by line send. Which makes sense for a
"psuedo-terminal". And they also apparently use a larger internal
buffer.
--
-- Stephe
next prev parent reply other threads:[~2014-10-05 18:19 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 [this message]
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
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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