PHPDay 2013 - High Performance PHP

High
Performance PHP
PHPDay 2013
Jonathan Klein
@jonathanklein
Saturday, May 18, 13

Slides, Links:
jkle.in/phpday

Some Etsy Stats
• 1.4 billion page views/month
• Almost $1B in sales last year
• Over 1M lines of PHP

Agenda
• Why Performance Matters
• Profiling PHP Applications
• Code Level Optimizations
• Big Wins
• Load Testing
• Takeaways

The Value of
Performance

Real World Examples
http://www.phpied.com/the-performance-business-pitch/

Real World Examples
• Firefox: -2.2 seconds = 15.4% more downloads

Real World Examples
• Shopzilla: -5 seconds = 7-12% increase in
revenue

Real World Examples
revenue
• Google: +400ms = 0.76% fewer searches

Real World Examples
revenue
• Google: +400ms = 0.76% fewer searches
• Amazon: +100ms = -1% revenue

~80% of page
load time takes
place on the client

...if your backend
is fast

A fast page load is 2 seconds
This means you have 400ms to get that
HTML off your server

But network time could be ~100ms
This means you have 400ms 300ms to
build the page

< 100ms feels instant
< 1 sec feels like flow
< 10 sec to keep user’s attention
http://www.nngroup.com/articles/response-times-3-important-limits/

Full Page Load – 2 Seconds

Base HTML – 400ms

Base HTML – 400ms
Server Generation Time – 300ms

Profiling PHP
Applications

Monitoring/Tracing
• Paid:
• Tracelytics (bought by AppNeta)
• AppDynamics (building a PHP solution)
• dynaTrace (building a PHP solution)
• New Relic (has a free option)
• Free:
• StatsD/Graphite
• xhprof

Monitoring/Tracing
• Paid:
• Tracelytics (bought by AppNeta)
• AppDynamics (building a PHP solution)
• dynaTrace (building a PHP solution)
• New Relic
• Free:
• StatsD/Graphite
• xhprof

StatsD (UDP packets)
$start = microtime(true);
/* script content */
$end = microtime(true);
StatsD::timing('foo.bar', $end - $start);
More Info: http://goo.gl/LbDPE

Graphite
• Written by Orbitz
• Real-time graphing engine for StatsD data
(among other things)
• http://graphite.wikidot.com/
• Architecture: http://www.aosabook.org/en/
graphite.html

Etsy Conversations PHP Time
Execution Count

Search Page PHP Time (95th Percentile)

Search Page
Execution Count

Stacked Search Timers

xhprof
• PHP Extension (need to install)
• http://pecl.php.net/package/xhprof
• Code level tracing
• Significant overhead, use in DEV only!
• Add ?xhprof=1 to URL
• Results in browser

Lesson:
Profile Your Code

Code Level
Optimizations

Writing Efficient PHP
Set max value before loop:
$max = count($rows);
for ($i = 0; $i < $max; $i++) {
echo $i;
}
require_once() is slow
Minimize use of define()
Yes, single quotes are slightly faster than double quotes, but...

Almost Every Micro-Optimization is
Worthless

http://phpbench.com/

Writing Efficient PHP
Set max value before loop:
$max = count($rows);
for ($i = 0; $i < $max; $i++) {
echo $i;
}
Okay, this one is pretty good

So Why Even Mention
Micro-Optimizations?

http://code.ﬂickr.net/2009/12/02/ﬂipping-out/

strtok() to implode()

Lesson:
Focus on the Big
Wins

“Premature optimization is the root of all evil”
- Donald Knuth

Upgrade PHP

Upgrade PHP
5.3 is ~20% faster than 5.2

Upgrade PHP
http://news.php.net/php.internals/36484

Upgrade PHP
5.4 is ~20-40% faster than 5.3

Upgrade PHP

Upgrade PHP
Upgrading 5.2 --> 5.4 gives a 45-70% improvement!

Upgrade PHP
http://php.net/migration53

Upgrade PHP

PHP 5.4 is 5 Times Faster than PHP 4
http://static.zend.com/topics/White-paper-PHP4-PHP5.pdf

Etsy’s Upgrade to PHP 5.4

Use an Opcode
Cache (APC)

Standard Page Execution

With An Opcode Cache

Opcode Cache
Vanilla settings: 30-40% improvement
Turn off APC Stat: additional ~2x
improvement
-- Understand what is happening here
http://www.slideshare.net/vortexau/improving-php-application-performance-with-apc-presentation

Cache Data in a
Key-Value Store

APC User Cache
<?php
$foo = "Hello, World!";
apc_store('some_key', $foo);
?>
<?php
var_dump(apc_fetch('some_key'));
?>
-------- Output --------
string(12) "Hello World!"

APC User Cache

APC User Cache
• Avoid fragmentation - keep utilization under 10%

APC User Cache
• Assign 1GB, only fill 100MB

APC User Cache
• Compress objects that are > 10KB before storing

APC User Cache
• Reduce garbage collection in the source of
apc_store()

APC User Cache
apc_store()
• Consider CDB

APC User Cache
apc_store()
• Consider CDB
• http://engineering.wayfair.com/moving-constants-out-of-apc-
and-into-cdb/

Memcached
• Usually a separate server
• In-memory key-value store
• Extremely simple and fast
• http://memcached.org/

APC vs. Memcached
APC User Cache Memcached
Local to the Server Shared Network Resource
Good for small objects Large or small objects
Good for mostly read
workloads
Can read and write quickly
Only one instance Can be clustered

Fix All Errors
• PHP 5.3: E_ALL | E_STRICT
• PHP 5.4: E_ALL
• Can also do error_reporting(-1);

Child Processes
4-6 processes per CPU core.
Beyond that just add servers.
(Test your app)

HipHop for PHP
• Developed/Open Sourced by Facebook
• Now a VM + JIT compilation
• 5x improvement in throughput over PHP 5.2
• http://developers.facebook.com/blog/post/2010/02/02/
hiphop-for-php--move-fast/
• https://www.facebook.com/notes/facebook-engineering/
speeding-up-php-based-development-with-hiphop-vm/
10151170460698920
• https://github.com/facebook/hiphop-php

Understand
Framework
Overhead

http://systemsarchitect.net/performance-benchmark-of-popular-php-frameworks/

Symfony is 20x
slower than raw
PHP

Load Testing

JMeter
• Open Source
• Generate load via a GUI or command
line
• Can watch req/s degrade with more
users
• Easy to use

Be Careful

Be Careful
• JMeter looks a lot like a DOS attack

Be Careful
• Make sure you know what is failing

Be Careful
• Look at monitoring while test is running

Be Careful
• Run in Production

Be Careful
• Run in Production
• Run a test, make a change, run it again

Takeaways

“How Fast IsYour Site?”

This is a terrible quesiton

Why is it terrible?

Why is it terrible?
• Lack of context

Why is it terrible?
• Lack of context
• Are we talking about average or a percentile?

Why is it terrible?
• Lack of context
• Server side time or client?

Why is it terrible?
• Lack of context
• Who is measuring it?

Why is it terrible?
• Lack of context
• When is it being measured?

Why is it terrible?
• Lack of context
• When is it being measured?
• Real users or synthetic?

We still have to answer it

Pick Tight SLAs
“The homepage of our site will load in
<300ms at the 80th percentile, measured
by sampling 10% of our real users over a
24 hour period every day at 8AM.”

Things to Remember

Things to Remember
• Measure and monitor your application

Things to Remember
• Focus on big wins

Things to Remember
• Run the latest (stable) version of PHP

Things to Remember
• Make sure you are using APC correctly

Things to Remember
• It’s always the database (stay in this room)

Things to Remember
• Caching is your friend

Things to Remember
• Caching is your friend
• Know what system resources you depend on

There is a lot more to talk about

Get in Touch
http://web-performance.meetup.com/
www.etsy.com/careers
jonathan@etsy.com
@jonathanklein

PHPDay 2013 - High Performance PHP

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