Use xdebug to analyze PHP programs and find performance bottlenecks

There is a famous 80-20 law in economics, which is quoted in programming: 80% of performance bottlenecks are caused by 20% of the code. With the help of PHP's XDebug extension, these 20% of code can be effectively found.

1. Installation and configuration

1. Download the XDebug extension for PHP at: http://xdebug.org/

2. Compile and install XDebug under Linux

tar -xzf xdebug-2.0.0RC3.gz
cd xdebug-2.0.0RC3
/usr/local/php/bin/phpize
./configure --enable-xdebug
cp modules/xdebug.so /usr/local/php/lib/php/extensions/no-debug-non-zts-20020429/

Note: /usr/local/php/lib/ php/extensions/no-debug-non-zts-20020429/Different PHP versions have different paths and do not have to be placed on this path. You can specify the location of xdebug.so in zend_extension_ts.

vi /usr/local/php/lib/php.ini

Modify php.ini, remove the PHP acceleration module, and add the following configuration information to support XDebug extension

[Xdebug]
zend_extension_ts="/usr/local/php/lib/php/extensions/no-debug-non-zts-20020429/xdebug.so"
xdebug.profiler_enable=on
xdebug.trace_output_dir="/tmp/xdebug"
xdebug.profiler_output_dir="/tmp/xdebug"
xdebug.profiler_output_name="script"
mkdir -p /tmp/xdebug
chmod 755 /tmp/xdebug
chown www:www /tmp/xdebug
/usr/local/apache/bin/apachectl -k restart

3. Client (Windows): WinCacheGrind Download address: http://sourceforge.net/projects/wincachegrind/

II , Analysis process

1. Visit your website and click various links on the homepage several times. XDebug generates the following files in the /tmp/xdebug directory:

usr_local_apache_htdocs_app_checknum_chknum_php_cachegrind.out
usr_local_apache_htdocs_app_login_showHeaderLogin_php_cachegrind.out
usr_local_apache_htdocs_app_play_play_php_cachegrind.out
usr_local_apache_htdocs_app_user_member_php_cachegrind.out
usr_local_apache_htdocs_tag_tags_php_cachegrind.out
usr_local_apache_htdocs_top_top_php_cachegrind.out

2. Copy the above files to Windows and use client software WinCacheGrind opened each file and found that the following PHP program took the longest time to execute:

/usr/local/apache/htdocs/tag/tags.php　　　　　　耗时840ms

3. Analysis results:

1, /usr/local/apache/htdocs/tag/tags.php

( 1) The longest time-consuming filter_tags function appears on line 158 of /usr/local/apache/htdocs/tag/tags.php:

$tags .= filter_tags($videos[$i]['tags'])." ";

(2) The filter_tags function is quoted from /usr/local/apache/htdocs/include /misc.php, the getForbiddenTags function is called 21 times by the filter_tags function. Most of the time spent by the filter_tags function is caused by the getForbiddenTags function. The content of the getForbiddenTags function is as follows:

function getForbiddenTags()
{
    $tagsPath=TEMPLATE_FILE_PATH."tags/forbidden_tags.txt";
    if(file_exists($tagsPath))
    {
        $fp = fopen($tagsPath, "r");
        $arrconf = array ();
        if ($fp) 
        {
            while (!feof($fp)) 
            {
                $line = fgets($fp, 1024);
                $line = trim($line);
                $rows = explode("#", $line);
                $coumns = explode("=", trim($rows[0]));
                if(""!=trim($coumns[0]))
                {
                     $arrconf[trim($coumns[0])] = trim($coumns[1]);
                }
            }
        }
        return $arrconf;
    }
}

(3) Analysis of the getForbiddenTags function shows that the PHP function trim was called 16827 times.

(4) Possible reasons for the bottleneck:

The 156 keywords to be filtered are stored line by line in the /usr/local/apache/template/tags/forbidden_tags.txt file, and the text database is not efficient .

The line-by-line reading function fgets and the function trim that removes blanks on both sides of a string or specified characters are inefficient under high load. You can test file reading functions such as fopen, fread, and fscanf for comparison.