bug#31138: Native json slower than json.el

[Eli Zaretskii]

> Cc: sebastien@chapu.is, yyoncho@gmail.com, 31138@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 16 Apr 2019 16:50:58 +0300
> 
> All right, my test script and results are attached. Here's how I run it:
> 
> sudo perf record -F 99 src/emacs -Q --batch -l ~/examples/elisp/json-test.el
> sudo perf report -n --stdio > perf-report.txt

Thanks.  I think we need to run this with a larger JSON, or maybe run
it several times in a loop.  Because there were too few samples in
this run, so we might see a biased picture due to overhead of stuff
that is done only once.

Also, please set gc-cons-threshold and gc-cons-percentage to very
large values, to prevent GC from biasing the profile even more.

> If you have certain recording or output format preferences, please let 
> me know.

The ASCII format is fine.

Was this an optimized build of Emacs or an unoptimized one?