M-x compile output sometimes delayed

M-x compile output sometimes delayed

[Dan Jacobson]

In makefile I have
z:
	set -x;until test $$((retrys++)) -gt 9; do sleep 4;done

I do M-x compile.  I see the output in fits and starts, not every 4
seconds.  Sometimes it comes out line by line, sometimes it takes me
hitting say even the Shift key to stimulate it into spitting out
output.  Odd, as my processor is 99% idle.
-- 
http://jidanni.org/ Taiwan(04)25854780

Re: M-x compile output sometimes delayed

[Eli Zaretskii]

Dan Jacobson wrote:
> 
> In makefile I have
> z:
>         set -x;until test $$((retrys++)) -gt 9; do sleep 4;done
> 
> I do M-x compile.  I see the output in fits and starts, not every 4
> seconds.  Sometimes it comes out line by line, sometimes it takes me
> hitting say even the Shift key to stimulate it into spitting out
> output.  Odd, as my processor is 99% idle.

I think you forget about I/O buffering.  Emacs runs subordinate processes
via a pipe, and pipes are buffered by the system.

In addition, Emacs only checks whether there was input from a subprocess
when it's not busy doing other things, so that could account for additional
delays.

Re: M-x compile output sometimes delayed

[Richard Stallman]

    I do M-x compile.  I see the output in fits and starts, not every 4
    seconds.

That certainly should not happen.  It does not fail for me, though.
Can anyone reproduce this and debug it?

Eli wrote:

    I think you forget about I/O buffering.  Emacs runs subordinate processes
    via a pipe, and pipes are buffered by the system.

Sure, but unless Emacs is busy, that should only result in a very
short delay before Emacs wakes up, reads the data, puts it in the
buffer, and displays it.  If Emacs fails to do this promptly,
that is indeed a bug in Emacs.

    In addition, Emacs only checks whether there was input from a subprocess
    when it's not busy doing other things, so that could account for additional
    delays.

That is true, but I get the impression that Emacs was not doing any
other computation in that test case.  He said the processor was 99%
idle, which it would not have been if Emacs had been running the whole
time.

Re: M-x compile output sometimes delayed

[Dan Jacobson]

Could the reason why
|In makefile I have
|z:
|	set -x;until test $$((retrys++)) -gt 9; do sleep 4;done
|
|I do M-x compile.  I see the output in fits and starts, not every 4
|seconds.  Sometimes it comes out line by line, sometimes it takes me
|hitting say even the Shift key to stimulate it into spitting out
|output.  Odd, as my processor is 99% idle.
Be related to me now having a 1 Ghz processor, and many GNU/Linux time
comparisons being only in 1 sec. granularity, so things that never
occurred during the same second before now do?  [which also causes a breakdown
of traditional Makefile checks etc., [oh great, no wonder they said
computing will never be the same, looks like I will now have to put
"sleep 1" "shims" all over my Makefiles] but that's only semi related here.]
-- 
http://jidanni.org/ Taiwan(04)25854780