Dtrace with PHP scripts works on FreeBSD8-STABLE!

[Alex Samorukov]

Hello,

I was able to compile [1] and and run PHP Dtrace provider on 
FreeBSD-STABLE. Everything works as expected and looks very cool. It 
works both from Apache (mod_php) and cli. If there are port commiters 
with dtrace experience - please, take it.

Below there is a small demo:

This is a test script:

<?php
/* useless dtrace demo script */

$file = file_get_contents("test.php"); /* classless func. */
$demo = new demoClass(); /* call constructor */
$demo->PrintTest();

class demoClass{
     function demoClass(){
     @chdir("/notexists");
     }
     function PrintTest(){
     echo "TEST\n";
     }
}
?>

This is the most basic output to demonstrate how provider works:

# dtrace -n 'php*::: /arg0/ 
{printf("\t\t%s%s%s",copyinstr(arg3),copyinstr(arg4),copyinstr(arg0))}'
dtrace: description 'php*::: ' matched 24 probes
dtrace: buffer size lowered to 2m
CPU     ID                    FUNCTION:NAME
   2  44455 php_dtrace_execute_internal:function-entry           
file_get_contents
   2  44457 php_dtrace_execute_internal:function-return          
file_get_contents
   2  44456 php_dtrace_execute:function-entry            
demoClass::demoClass
   2  44455 php_dtrace_execute_internal:function-entry           chdir
   2  44457 php_dtrace_execute_internal:function-return          chdir
   2  44458 php_dtrace_execute:function-return           
demoClass::demoClass
   2  44456 php_dtrace_execute:function-entry            
demoClass::PrintTest
   2  44458 php_dtrace_execute:function-return           
demoClass::PrintTest

As you could see there is information about all functions (and 
classnames) in our test.

Also there is a possibility to trace syscalls used by PHP function. This 
is output from ./php_syscolors.d (with minor modifications):
for the file_get_contents (reads file to variable):

1  16019/100898          6          test.php:4    func     -> 
file_get_contents
1  16019/100898         18                 ":-    syscall    -> __getcwd
1  16019/100898          8                 ":-    syscall <- __getcwd
1  16019/100898          8                 ":-    syscall    -> 
clock_gettime
1  16019/100898          4                 ":-    syscall <- clock_gettime
1  16019/100898          5                 ":-    syscall    -> open
1  16019/100898          9                 ":-    syscall <- open
1  16019/100898          5                 ":-    syscall    -> fstat
1  16019/100898          5                 ":-    syscall <- fstat
1  16019/100898          4                 ":-    syscall    -> lseek
1  16019/100898          4                 ":-    syscall <- lseek
1  16019/100898          5                 ":-    syscall    -> fstat
1  16019/100898          4                 ":-    syscall <- fstat
1  16019/100898          4                 ":-    syscall    -> read
1  16019/100898          6                 ":-    syscall <- read
1  16019/100898          9                 ":-    syscall    -> read
1  16019/100898          5                 ":-    syscall <- read
1  16019/100898          4                 ":-    syscall    -> read
1  16019/100898          4                 ":-    syscall <- read
1  16019/100898          5                 ":-    syscall    -> close
1  16019/100898         10                 ":-    syscall <- close
1  16019/100898          8          test.php:4    func <- file_get_contents

Of course it is possible to use aggregations, filtering and all other 
dtrace features.

Problems: I found that buffer size in dtrace is always about 2m. I am 
using a lot of events while trying to debug running web server.

Todo: latest PHP alpha releases include dtrace support internally (and 
it is extended, compared to this pecl extension). Currently build 
failing on BSD and i had no time to investigate problem source (i think 
they are using some ugly linker hacks). It would be great to get it 
fixed before PHP release to have it in FreeBSD out of the box.

[1] http://www.freebsd.org/cgi/query-pr.cgi?pr=158983