Performance Tuning in PHP
PHPCAMP 2008
th
20 Sept.
Jignesh Thummar
<jignesh.thummar@gmail.com>

Anatomy of PHP
PHP File ●
This cycle happens
for all included files
not only for main()
Zend Compiler script.
●
Generally most of
Execution at Zend Engine the time
consumption take
place at Compiler.
End User

Opcodes
0 EXT_STMT
1 ASSIGN !0, 'Enjoy+the+PHPCamp%2C+'
<?php 2 EXT_STMT
$greet = 'Enjoy the PHPCamp, '; 3 ASSIGN !1, 'Jignesh'
$name = 'Jignesh'; 4 EXT_STMT
5 ZEND_ISSET_ISEMPTY_VAR 1 ~2 'name'
if(isset($name)){
6 JMPZ ~2, ->11
$say = $greet . $name; 7 EXT_STMT
}else{ 8 CONCAT ~3 !0, !1
9 ASSIGN !2, ~3
$say = $greet . 'human';
10 JMP ->14
}
11 EXT_STMT
echo $say; 12 CONCAT ~5 !0, 'human'
?> 13 ASSIGN !2, ~5
14 EXT_STMT
15 ECHO !2
Opcodes generated using Vulcan Logic
16 EXT_STMT
Disassembler (VLD) by Derick Rethans.
http://pecl.php.net/packages/VLD/ 17 RETURN 1
18* ZEND_HANDLE_EXCEPTION

Opcode/Compiler cache
●
Each PHP script (also for included files)
compiled only once and store into cache
●
during the next request it will not compile
again but directly pick it up from cache for
execution
●
reduce file I/O (stats calls) as it is being
executed from the cache(memory) rather
than disk
●
the fastest and easiest solution for faster
execution

Opcode/Compiler cache
PHP File
Opcode Cache
Cacher
hit/store
Zend
Compiler
fetch
opcodes
Parse/Execute
Opcodes
End User

APC
●
Alternate PHP Cache
●
A free, open source and robust framework
for caching and optimizing PHP
intermediate code.
●
maintained by core PHP developers
●
users
Yahoo!
Facebook
Wikipedia and many more

Installation
$pecl install APC
OR Source Compilation
#wget http://pecl.php.net/get/APC
#tar -zxvf APC-3.0.x.tar.gz
#cd APC-3.0.x
#phpize
#./configure
#make
#make install
#cp modules/apc.so /full/path/to/ext/apc.so
Windows user
Download it from : http://pecl4win.php.net/

Enable APC
●
edit php.in : extension=apc.so
●
restart apache
Web console to monitor APC Info
copy apc.php from apc source directory to document root

.ini directives
●
apc.shm_size = 30 (in MB)
●
apc.stat = 1 (by default)
- check if files has been modified on every request
- if apc.stat = 0, requires restart webserver on update or
apc_clear_cache()
- use include('/webroot/conf.php') instead of
include('conf.php')
●
apc.filters = <regex>
a comma separated POSIX regex. default value is “-”
●
apc.cache_by_default = true
false - files are only cached if matched by a positive filter

more .ini directives
– apc.ttl = 0 (by default)
Time to Live in cache - seconds
– apc.write_lock = 1 (by default)
only one process at a time instead of waiting on a lock
– apc.num_files_hint = 1000 (by default)
maximum number of files expect to be stored in memory
– apc.max_file_size = 1M (by default)
maximum file size that will be allowed in the apc cache
– apc.file_update_protection=1(protect for 2 sec)
– apc.include_once_override = 0 (by default)

APC user cache
●
bool apc_add(string $key, mixed $var [, int $ttl ])
●
bool apc_store(string $key, mixed $var [, int $ttl ])
●
mixed apc_fetch(string $key)
●
bool apc_delete(string $key)
.ini settings
apc.user_ttl = 0
apc.user_entries_hint = 4096

page cache with APC
<?php
$key = \"PAGE::\".$_SERVER['REQUEST_URI'];
$pagecontents = apc_fetch($key);
if($pagecontents) {
echo $pagecontents;
exit;
}
ob_start();
// write your code
$pagecontents = ob_get_flush();
apc_store($key, $pagecontents);
?>

handling constants through APC
●
bool apc_define_constants(string $key, array $constants
[, bool $case_sensitive])
●
bool apc_load_constants(string $key [,bool $case_sensitive])
<?php
$constants = array(
'NAME' => 'Jignesh',
'AGE' => 24,
'LOCATION' => 'Pune',
);
apc_define_constants('jignesh_info', $constants);
apc_load_constants('jignesh_info');
echo NAME,',',AGE,',',LOCATION;
?>

more functions
●
bool apc_compile_file ( string $filename )
●
bool apc_clear_cache ([ string $cache_type ] )
●
array apc_cache_info ([string $cache_type[,bool $limited ] ] )
●
array apc_sma_info ([ bool $limited ] )

other opcode cacher
●
XCache : http://xcache.lighttpd.net
●
IonCube: http://www.ioncube.com/sa_encoder.php
●
Zend Platform: http://www.zend.com/en/products/platform/
●
Turck MMCache:
http://turck-mmcache.sourceforge.net/index_old.html
●
EAccelerator: http://www.eaccelerator.net/

Benchmarking
Apache Bench
‣ ab utility bundled with Apache
http_load
‣ http://www.acme.com/software/http_load/
Siege
‣ http://www.joedog.org/JoeDog/Siege
Benchmark PEAR package
‣ http://pear.php.net/package/Benchmark

Apache Bench
$ab -c 20 -n 50 <webserver_url>
Concurrency Level: 20
Time taken for tests: 0.48937 seconds
Complete requests: 50
Non-2xx responses: 52
Total transferred: 10504 bytes
HTML transferred: 0 bytes
Requests per second: 1021.72 [#/sec] (mean)
Time per request: 19.575 [ms] (mean)
Time per request: 0.979 [ms] (mean, across all concurrent
requests)
Transfer rate: 204.34 [Kbytes/sec] received

http_load
$http_load -rate 20 -seconds 5 <file_name>
99 fetches, 2 max parallel, 9702 bytes, in 5.00098 seconds
98 mean bytes/connection
19.7961 fetches/sec, 1940.02 bytes/sec
msecs/connect: 0.470556 mean, 0.635 max, 0.221 min
msecs/first-response: 1.40029 mean, 2.106 max, 1.175 min
HTTP response codes:
code 200 -- 99

Siege
$siege -b -r 20 -t 5S <server_url>
Transactions: 677 hits
Availability: 100.00 %
Elapsed time: 5.84 secs
Data transferred: 5.39 MB
Response time: 0.13 secs
Transaction rate: 115.92 trans/sec
Throughput: 0.92 MB/sec
Concurrency: 14.67
Successful transactions: 677
Failed transactions: 0
Longest transaction: 0.99
Shortest transaction: 0.04

serving static contents
●
Apache's mod_php is designed for dynamic contents.
●
Every Apache child used fair chunk of memory when
it's executed with mod_php.
●
Serving static content like image, JS, CSS, HTML etc.
with mod_php is more costly
●
Other option:
lighttpd
thttpd
Boa
And nowadays S3 (Amazon Web Services)

Lets tune PHP code

include/require_once - once more
lstat64(\"/srv/www/htdocs/incl_test\", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64(\"/srv/www/htdocs/incl_test/a.php\", {st_mode=S_IFREG|0644, st_size=39, ...}) = 0
open(\"/srv/www/htdocs/incl_test/a.php\", O_RDONLY) = 4
lstat64(\"/srv/www/htdocs/incl_test\", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64(\"/srv/www/htdocs/incl_test/a.php\", {st_mode=S_IFREG|0644, st_size=39, ...}) = 0
open(\"/srv/www/htdocs/incl_test/a.php\", O_RDONLY) = 4
In PHP 5.2>= this will allow PHP to avoid opening the file
twice.

file path problem
– While it is convenient and easy to do include “foo.php”
and have it work, internally.
– it leads to significant overhead in system.
– Whenever possible you should use full paths, that
require no resolution in PHP.
getcwd(\"/srv/www/htdocs/perf_demo\", 4096) = 26
lstat64(\"/srv/www/htdocs/incl_test/a.php\", {st_mode=S_IFREG|0644, st_size=39, ...}) = 0
open(\"/srv/www/htdocs/incl_test/a.php\", O_RDONLY) = 4
getcwd(\"/srv/www/htdocs/perf_demo\", 4096) = 26
lstat64(\"/srv/www/htdocs/perf_demo/b.php\", {st_mode=S_IFREG|0644, st_size=39, ...}) = 0
open(\"/srv/www/htdocs/perf_demo/b.php\", O_RDONLY) = 4
Generate system calls using $strace -e trace=file php <file_name.php>

include_path
my include_path is
\".:/usr/share/php5:/usr/share/php5/PEAR:/srv/www/\"
How to fix this?

sessions
●
session.auto_start = 1 (by default 0)
●
PHP's session extension by default store
sessions in to each file within single
directory.
●
many files into one directory reduce access
speed
●
instead, store session in different directory
●
session.save_path = “N;/var/lib/php5”
●
N – no. of directory level e.g.
/tmp/4/b/1/e/3/sess_14879g

sessions
●
PHP's default session handler is file system
●
instead, it can be stored into cache
●
let's say in memcache
●
session.save_handler = memcache
session.save_path = “tcp://127.0.0.1:11211”
●
using APC's add/fetch/delete

static keyword
●
makes them accessible without needing an
instantiation of the class
●
so it's faster
●
public static function a( ) is faster compare to
public function a( )
●
quick benchmark for it.

Class Constants
●
define( ) is expensive
●
Class Constants are parsed at compile time.
So no execution overhead.
●
faster lookup due to smaller hash.
●
benchmark for it

miss use of Constants
●
$foo[name] = 'Jignesh';
●
converted into strtolower
●
hash lookups
●
E_NOTICE error message generated
●
temporary string being generated on the
during the execution
●
And of course it's slower
●
Let's benchmark for it.

for() loop optimization
Don't use functions in for() loop.
<?php
for ( $i = 1; $i < count($array); $i++ ) { }
?>
instead use,
<?php
$count = count($array);
for ( $i = 1; $i < $count; $i++ ) { }
?>

which is faster?
What’s the difference between:
isset($user['NAME'])
and
array_key_exists('NAME', $user)
Let's generate opcodes, more opcode less
performance

Performance Tips
●
Mostly people have only one solution
●
habitual to use DATABASE for information storage
●
Improper use of this resource can lead to significant
and continuously increasing performance loss.
●
Try to cache at different level
●
Avoid reg-ex, PHP's string functions are faster
●
Avoid magic calls - __get/__set/__autoload/__call.
●
There are lots of PHP's built in functions; PEAR, PECL
packages
●
chances are there what you need is already available

What to do, when you are stuck?
●
Use Benchmarking Tools
●
Find bottleneck in your code
●
It might take time to do optimization
●
There is no any golden rule for it
●
make your hand dirty

Finally
Premature optimization is the root of all evil.
- Donald Knuth

Resources
http://pecl.php.net/apc

Thanks
Any other idea?