bug#895: slow processing of process output

[Dan Nicolaescu <dann@ics.uci.edu>]

Dan Nicolaescu <dann@ics.uci.edu> writes:

  > emacs -Q -nw
  > M-x rgrep RET emacs RET *.el RET PATH_TO_EMACS_SOURCE_TREE/lisp RET
  > 
  > takes a few minutes.  The output is about 9000 lines.
  > 
  > Running the correspondind command:
  > 
  > find . \( -path \*/SCCS -o -path \*/RCS -o -path \*/CVS -o -path \*/MCVS -o -path \*/.svn -o -path \*/.git -o -path \*/.hg -o -path \*/.bzr -o -path \*/_MTN -o -path \*/_darcs -o -path \*/\{arch\} \) -prune -o -type f \( -name *.el \) -print0 | xargs -0 -e grep -i -nH -e emacs
  > 
  > from a shell (and redirecting the output to a file) takes less than one second.

One more data point:

emacs -Q -nw

M-x lgrep RET emacs RET *.el RET PATH_TO_EMACS_SOURCE_TREE/lisp RET

takes 33 seconds.  It runs the command:  grep -i -nH -e emacs *.el

M-x shell RET time grep -i -nH -e emacs *.el
0.087u 0.020s 0:01.60 6.2%      0+0k 0+0io 0pf+0w
              ^^^^^^^
              A lot less than 33 seconds.