PHP with open_basedir performance problem

[Thomas Hurst]

* Miroslav Lachman (000.fbsd at quip.cz) wrote:

> I found a painful performance problem with Apache + PHP 5 when
> open_basedir directive is enabled.

Looks like it's lstat()/readlink() overhead.  I wrote a simple bit of
PHP similar to yours, but doing 10 * 1000 require "foo/%d/%d.php" calls
from the command line:

-% time ktrace php main.php
Real: 0:09.61 CPU: 99.8% (3.725/5.885) Page: 0 Swap: 0 I/O: (0/0) Mem:
13704

-% time ktrace php -d open_basedir='/home/freaky/openbasedir/foo'
main.php
Real: 0:16.21 CPU: 86.4% (8.185/5.840) Page: 0 Swap: 0 I/O: (0/0) Mem:
13696

Without open_basedir, a simple script to parse the kdump syscall times
produces:

   lstat        : 1.147s/70065 calls = 0.000s per call.  Max=0.000s Min=0.0000s
   fcntl        : 0.408s/60007 calls = 0.000s per call.  Max=0.000s Min=0.0000s
sigprocmask     : 0.229s/40311 calls = 0.000s per call.  Max=0.000s Min=0.0000s
    open        : 0.223s/10085 calls = 0.000s per call.  Max=0.000s Min=0.0000s

With open_basedir:

   lstat        : 4.182s/270065 calls = 0.000s per call.  Max=0.005s Min=0.0000s
readlink        : 2.142s/10006 calls = 0.000s per call.  Max=2.020s Min=0.0000s
   fcntl        : 0.421s/60007 calls = 0.000s per call.  Max=0.002s Min=0.0000s
   close        : 0.295s/10085 calls = 0.000s per call.  Max=0.115s Min=0.0000s
sigprocmask     : 0.237s/40311 calls = 0.000s per call.  Max=0.000s Min=0.0000s
    open        : 0.222s/10085 calls = 0.000s per call.  Max=0.000s Min=0.0000s

The top two syscalls seem to account for most of the 6.mumble seconds of
additional runtime; presumably these are much cheaper on Linux.

-- 
Thomas 'Freaky' Hurst
    http://hur.st/