PHP-code profiling. XHprof — hierarchical profiler with html-interface

Setting reports interface

XHprof module has an ability to build text and graphic reports.

There are two folders xhprof_html (access to UI и GUI) and xhprof_lib (library for data analysis) in installation directory.

Second folder depending on OS should be placed in /usr/local/share/php/ or /usr/local/lib/php/ (providing global access to library by that).

Then an access to UI should be made. For that a new domain or subdomain must be created on server and a folder xhprof_html (as an option xhprof_lib can also be put here) must be put into it.

To start a profiler:

xhprof_enable(XHPROF_FLAGS_CPU + XHPROF_FLAGS_MEMORY);

Here XHPROF_FLAGS_CPU and XHPROF_FLAGS_MEMORY indicate to a profiler that data needs to be collected, processor usage and OS.

Disabling work of profiler:

$xhprof_data = xhprof_disable();

Saving data:

include_once dirname(__FILE__) . '/xhprof_lib/utils/xhprof_lib.php';
include_once dirname(__FILE__) . '/xhprof_lib/utils/xhprof_runs.php';
$namespace = $_SERVER['SERVER_NAME']; 
$xhprof_runs = new XHProfRuns_Default(); 
$run_id = $xhprof_runs->save_run($xhprof_data, $namespace);

Generating link for report view:

print sprintf('http://<xhprof_domain>/xhprof_html/index.php?run=%s&source=%s', $run_id, $profiler_namespace);. 

Graphic interface

XHprof also has an in-built graphic interface.

As for me they don’t have any noticeable value but I still can't help mentioning it :) .

For its proper operation Graphviz application must be installed on the server (it's included into most Linux distributives). html interface being configured you can use graphic one without any other moves (link [View Full Callgraph] in reports).

After the first usage one can come across the following error:

Warning: proc_open() [function.proc-open]: open_basedir restriction in effect. File(/dev/null) is not within the allowed path(s)

It means that a user under whose name the script has been run has no access to null device (/dev/null). Two options: allow such access with the help of property open_basedir в php.ini or change line 108 of file /xhprof_lib/utils/callgraph_utils.php replacing "/dev/null" by any value to which our script will have access (for example I replaced by "/tmp/xhprof_stderr" for testing).

Profiling “live” applications

It’s clear that profiling in test environment may differ a lot from what we have on live site.

That’s why I can’t help mentioning one important factor about XHprof: this module was used for work with live applications. And it has native realization which implies excellent efficiency.

So it can be easily used on live projects. For example, a launch can be done only once in hundred requests to server:

if (rand(1, 100) == 1) { 
   xhprof_enable(XHPROF_FLAGS_MEMORY); 
   $xhprof_enable = TRUE; 
 } 

// application execution 

 if ($xhprof_enable) { 
   $xhprof_data = xhprof_disable(); 
   // saving data 
 }

Profiler also has an in-built “Lightweight Sampling” mode. Profiling will be executed every 100 milliseconds after this mode is on. To turn it on start/stop function of profiler should be replaced by xhprof_sample_enable (instead of xhprof_enable), xhprof_sample_disable (instead of xhprof_disable) .

Additional information

The most extensive information about the profiler can be found on its web developers’ page (by the way it’s not just somebody, it’s FaceBook Inc itself).