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Date: Fri, 5 Aug 2016 17:17:13 +0200
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To: Matt Wilmas <php_lists@realplain.com>
Cc: lp_benchmark_robot@intel.com, PHP internals <internals@lists.php.net>, 
	langperf@lists.01.org
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Subject: Re: [PHP-DEV] UGLY Benchmark Results for PHP Master 2016-08-05
From: nikita.ppv@gmail.com (Nikita Popov)

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On Fri, Aug 5, 2016 at 4:30 PM, Matt Wilmas <php_lists@realplain.com> wrote:

> Hi all,
>
> ----- Original Message -----
> From: <lp_benchmark_robot@intel.com>
> Sent: Friday, August 05, 2016
>
> Results for project PHP master, build date 2016-08-05 06:26:56+03:00
>> commit: 65b6f20
>> previous commit: 69a72df
>> revision date: 2016-08-04 22:27:42+02:00
>> environment: Haswell-EP
>> cpu: Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz 2x18 cores, stepping 2,
>> LLC 45 MB
>> mem: 128 GB
>> os: CentOS 7.1
>> kernel: Linux 3.10.0-229.4.2.el7.x86_64
>>
>> Baseline results were generated using release php-7.0.0, with hash
>> 60fffd2 from
>> 2015-12-01 04:16:47+00:00
>>
>> ------------------------------------------------------------
>> -------------------------------
>>                        benchmark   relative   change since   change since
>> current rev run
>>                                    std_dev*       last run       baseline
>> with PGO
>> ------------------------------------------------------------
>> -------------------------------
>> :-|   Wordpress 4.2.2 cgi -T10000      0.18%         -0.20%
>> 5.10% 7.48%
>> :-|       Drupal 7.36 cgi -T10000      0.17%         -0.24%
>>  -0.86% 5.31%
>> :-|   MediaWiki 1.23.9 cgi -T5000      0.11%          0.22%
>>  -0.13% 3.80%
>> :-)           bench.php cgi -T100      0.01%          1.06% .28%
>>  -7.09%
>> :-)      micro_bench.php cgi -T10      0.01%          4.09%
>>  15.14% 1.66%
>> :-(      mandelbrot.php cgi -T100      0.15%         -6.51%
>>  28.51% 5.76%
>> ------------------------------------------------------------
>> -------------------------------
>>
>
> Anyone know what has happened with the Wordpress improvement this week?
> This is 3 reports in a row that show ~5%.
>
> Did I miss some substantial commit(s)?
>
> Thanks for any insight!


Thanks for pointing this out.

This is caused by the change to array_slice() as part of
https://github.com/php/php-src/commit/e730c8fc90299789a7f551cb7142e182952d92e0#diff-497f073aa1ab88afcb8b248fc25d2a12R3014
.

As a consequence of this change, an array_slice() on an array with rc=1
references will now not return these references in the result. (This is the
correct behavior -- previously it instead dropped the references in the
original array, which is not wrong either, but non-standard.)

It looks like Wordpress is passing these arrays to call_user_func_array()
with a function that expects a reference argument:

call_user_func_array($the_['function'], array_slice($args, 0, (int)
$the_['accepted_args']));

And this results in:

nikic@saturn:~/php-src-fast$ sapi/cgi/php-cgi -c php.ini -T1
../wordpress-4.1/index.php | grep Warning
<b>Warning</b>:  Parameter 1 to wp_default_styles() expected to be a
reference, value given in
<b>/home/nikic/wordpress-4.1/wp-includes/plugin.php</b> on line
<b>571</b><br />
<b>Warning</b>:  Parameter 1 to wp_default_scripts() expected to be a
reference, value given in
<b>/home/nikic/wordpress-4.1/wp-includes/plugin.php</b> on line
<b>571</b><br />

So essentially, we're winning 5% because these two calls do not occur...

Nikita

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