bug#64735: 29.0.92; find invocations are ~15x slower because of ignores

[Eli Zaretskii]

> Date: Sat, 29 Jul 2023 03:12:34 +0300
> From: Dmitry Gutov <dmitry@gutov.dev>
> Cc: luangruo@yahoo.com, sbaugh@janestreet.com, yantar92@posteo.net,
>  64735@debbugs.gnu.org
> 
> It seems like per-chunk overhead is non-trivial, and affects GC somehow 
> (but not in a way that just any string would).
> 
> In this test, by default, the output produces ~6000 strings and passes 
> them to the filter function. Meaning, read_and_dispose_of_process_output 
> is called about 6000 times, producing the overhead of roughly 0.2s. 
> Something in there must be producing extra work for the GC.
> 
> This line seems suspect:
> 
>         list3 (outstream, make_lisp_proc (p), text),
> 
> Creates 3 conses and one Lisp object (tagged pointer). But maybe I'm 
> missing something bigger.

I don't understand what puzzles you here.  You need to make your
descriptions more clear to allow others to follow your logic.  You use
terms you never explain: "junk objects", "number of strings in the
heap", "per-chunk overhead" (what is "chunk"?), which is a no-no when
explaining complex technical stuff to others.

If I read what you wrote superficially, without delving into the
details (which I can't understand), you are saying that the overall
amount of consing is roughly the same.  This is consistent with the
fact that the GC times change only very little.  So I don't think I
see, on this level, what puzzles you in this picture.