Re: Deffering redisplay in COMINT

[Stefan Monnier <monnier@iro.umontreal.ca>]

> but that's what I have to live with).  Without the filter and 
> auto-hscroll-mode engaged, the results take nearly 30 seconds to 
> complete under Emacs.  (It is nearly instantaneous outside of Emacs.)  
> With the filter you suggest, the results take about 8-10 seconds with 
> a noticeable stutter between each row.  With the solution I had 
> developed (buffering the long lines in a buffer and restoring them at 
> the end of output), the results scroll by quickly in about 2-3 seconds, 
> but then it hesitates at the end (as it restores the long lines in the 
> buffer), for another 2-3 seconds.  So just reducing the horizontal 
> scrolling is giving us the big payback and the more complex 
> gymnastics is probably not worth code cost.

Hmm... I'm wondering why the "one line at a time" approach ends up
slightly slower than your more complex approach.  Using a single string
occurs an O(N^2) overhead (where N is the line length: we receive O(N)
packets per line and for each package we do a concat which costs O(N)),
so that might be the reason (which is why I suggested using a list of
strings, tho it makes detection of the prompt more cumbersome), but for
8KB lines it's not clear it would be that bad.

Could you M-x profiler-start ... M-x profiler-report around your tests
to see where the time is spent?


        Stefan