Re: M-x grep is too slow

[Jesper Harder]

Richard Stallman <address@hidden> writes:

>     Something has made `M-x grep' unbearably slow.  With 'emacs -Q' this
>     command
>
>        M-x grep -nH -e while emacs/lisp/gnus/*.el
>
>     took over 20 minutes to complete -- I lost patience after that and
>     killed Emacs, so it might actually take hours.  For comparison the
>     same command takes 2-3 s in Emacs 21.3 and 1 s on the command line.
>
> In what function is it spending most of its time?
>
> You can set debug-on-quit to t and try typing C-g a few times,
> and save the backtraces, then continue.  I doubt it will take
> more than a handful of times before you see the pattern.

Processing the output from the grep command in the *grep* buffer is
asynchronous, so the backtrace

    Debugger entered--Lisp error: (quit)

doesn't really reveal anything useful.

When I scroll to the bottom of the *grep* buffer I can see that after
a short while the insertion of new text gets very slow -- characters
are inserted at a rate of about 1 character per second.

-- 
Jesper Harder                                <http://purl.org/harder/>