Beefy Boxes and Bandwidth Generously Provided by pair Networks
Just another Perl shrine
 
PerlMonks  

Re^3: Can someone please write a *working* JSON module

by NERDVANA (Hermit)
on Oct 24, 2021 at 14:14 UTC ( #11137972=note: print w/replies, xml ) Need Help??


in reply to Re^2: Can someone please write a *working* JSON module
in thread Can someone please write a *working* JSON module

eval makes JSON::XS even slower than JSON::PP
seriously - it's 10 to 100 times slower to use eval() rather than a native decode_json() in a mod_perl production webserver on non-trivial data

Your experience seems to differ from everyone else's experience. This is probably why all the JSON module authors decided it was fine to use croak. Please show some kind of benchmark if you want to convince anyone.

I just ran a benchmark (command line, on a laptop, perl 5.34) and see that for extremely small json decodes of 1 object with one key, the eval is as high as 20% overhead on the fastest XS modules (but still 2.5+ million per second). It's a ~0% difference for JSON::PP (mine actually ran the eval faster than without, but that probably indicates the noise level in the benchmark as a whole). This assumes valid json - of course for invalid JSON, triggering exceptions would be slower than a parser that returns undef, but if you're worried about denial of service, I think you'll run out of bandwidth before running out of processor to catch the exceptions.

For extremely large JSON texts, the eval overhead is lost in the noise. (essentially no difference)

$ perl benchmark-eval.pl 
long_json: 2468099
            (warning: too few iterations for a reliable count)
                    Rate pp_small pp_small_eval xs_small_eval cxs_small_eval xs_small cxs_small
pp_small         77101/s       --           -2%          -96%           -96%     -97%      -97%
pp_small_eval    78309/s       2%            --          -96%           -96%     -97%      -97%
xs_small_eval  2083333/s    2602%         2560%            --            -4%     -15%      -17%
cxs_small_eval 2173913/s    2720%         2676%            4%             --     -11%      -13%
xs_small       2439024/s    3063%         3015%           17%            12%       --       -2%
cxs_small      2500000/s    3142%         3092%           20%            15%       3%        --
                 Rate pp_long_eval pp_long cxs_long_eval cxs_long xs_long_eval xs_long
pp_long_eval  0.596/s           --     -0%          -98%     -98%         -98%    -98%
pp_long       0.597/s           0%      --          -98%     -98%         -98%    -98%
cxs_long_eval  24.4/s        3993%   3983%            --      -1%         -18%    -18%
cxs_long       24.5/s        4018%   4008%            1%       --         -18%    -18%
xs_long_eval   29.9/s        4909%   4897%           22%      22%           --      0%
xs_long        29.9/s        4909%   4897%           22%      22%           0%      --

Here's my benchmark: feel free to adjust it in such a way that it shows your 10x - 100x slowdown, and post for us to look at.

use v5.20; use warnings; use Benchmark qw( :hireswallclock cmpthese ); use JSON::PP (); use JSON::XS (); use Cpanel::JSON::XS (); my $json_pp= JSON::PP->new; my $json_xs= JSON::XS->new; my $json_cxs= Cpanel::JSON::XS->new; my $small_json_string= q|{"test":1}|; sub random_data { return { map { rand() => $_[0]? random_data($_[0]-1) : rand() } 1..4 +0 } } my $long_json_string= $json_xs->encode(random_data(2)); say "long_json: ".length $long_json_string; cmpthese(1000000, { pp_small_eval => sub { eval { !$json_pp->decode($small_json_string) + } }, xs_small_eval => sub { eval { !$json_xs->decode($small_json_string) + } }, cxs_small_eval => sub { eval { !$json_cxs->decode($small_json_string +) } }, pp_small => sub { !$json_pp->decode($small_json_string) }, xs_small => sub { !$json_xs->decode($small_json_string) }, cxs_small => sub { !$json_cxs->decode($small_json_string) }, }); cmpthese(40, { pp_long_eval => sub { eval { !$json_pp->decode($long_json_string) } + }, xs_long_eval => sub { eval { !$json_xs->decode($long_json_string) } + }, cxs_long_eval => sub { eval { !$json_cxs->decode($long_json_string) +} }, pp_long => sub { !$json_pp->decode($long_json_string) }, xs_long => sub { !$json_xs->decode($long_json_string) }, cxs_long => sub { !$json_cxs->decode($long_json_string) }, });

Edit: Removed my comment about threaded/nonthreaded perl, since it was a strawman argument.

Replies are listed 'Best First'.
Re^4: Can someone please write a *working* JSON module
by Anonymous Monk on Oct 26, 2021 at 10:40 UTC
    Try 'strings' instead if sub{}s for less noisy benchmark

Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: note [id://11137972]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others cooling their heels in the Monastery: (4)
As of 2023-01-30 04:31 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found

    Notices?