analysis and performance information systems 337 prof. harry plantinga
Post on 21-Dec-2015
217 Views
Preview:
TRANSCRIPT
Analysis and Performance
Information Systems 337
Prof. Harry Plantinga
Analysis
Your boss says "Who's visiting our site? Where are they coming from? What pages are popular? What paths are users taking through the site? What are the problem pages where we lose visitors?"
Analysis options: Read the raw logfile Set up a logfile analysis program Sign up for Google Analytics
Google Analytics
An amazing tool… Where do my customers live? What path do they take through the site? What links are popular? Would a certain change improve the site?
(A/B testing)
How to add Google Analytics to a web site? Sign up for GA, install the google_analytics
module
Suppose…
You set up a new web site using Drupal
Performance is mediocre What was a site in the top 5% (for speed) drops
near the bottom… 5 seconds for a page load 0.75sec minimum for every file served high server load averages occasionally, load average shoots up and server
crashes
What to do?
Minimize download time
Reduce the number of hits (stylesheets, images) per pageview Use Drupal's CSS and JS optimization (although
they didn't exist in Drupal 4…)[ Reduced from >30 to about 20 files per pageview
(stylesheets, artwork, etc) this way] Can also minimize javascript
Limit 2 files at once per server Any way to improve this?
Second domain name
Add a second server on a different domain name Serve static files (artwork, stylesheets, etc)
from a separate server Allow 4 files to be downloaded at once between
the two domain names Can turn on maximum caching for static files
Caching
Turn on Drupal's page cache
Make sure users' browser cache works as well as possible Static content should never expire Change filename for revised files Static server: add an Expires or Cache-control
header: make sure content doesn't expire
Still, 40-60% of visitors come with an empty cache…
Optimize artwork
Make sure artwork files are small optimize in Photoshop or another program
Many small files == slow. How to reduce? combine artwork into one background image use jQuery to round corners use CSS Sprites use inline images in stylesheets with data: urls
Reduce download times
80-90% of wait time is downloading content
More ideas Compress components
Accept-Encoding: gzip, deflate? Then deflate! Apache: use mod_deflate
Use a content delivery network E.g. Akami Can improve av. response time 20% or more
Make pages appear faster
Stylesheets at the top, so pages can be rendered right away
Scripts at the bottom
Specify image dimensions
Minimize expensive page components
Page Speed
Google Page Speed tools help identify ways to improve performance Firebug add-on for Firefox Apache module mod_pagespeed
Problems remain?
At this point we still had very slow page display times and occasional load average spike/crash
How to debug?
What are the possible server performance bottlenecks?
Server Bottlenecks
Possible server bottlenecks Is the CPU maxed out? Running out of RAM Disk speed, transactions per second Network bandwidth Database capacity
How to test?
Disk maxed out?
Check disk activity (reads vs. writes) vmstat on linux performance monitor on windows or write your own…
If pegged, find cause excessively verbose logging? background process, e.g. backups? poorly configured database? too many database writes? some other bad algorithm?
Running out of bandwidth?
Get a bigger pipe
Or, send less data smaller artwork better caching gzip compression
Running out of RAM?
Check with linux top or free, performance monitor, etc.
Each server process takes 20-100 MB or more
Each Apache or Drupal module takes more
Our crashes were due to running out of RAM, then swap space
Solutions? Set MaxClients appropriately Turn down Keepalive time! (Default 15, to 2?) MaxRequestsPerChild to lower number, e.g. 300 Get more RAM
Running out of CPU?
Check with top (linux/mac) or performance monitor (windows)
PHP is interpreted
Each request: load, compile all the code… This was taking us something like 0.5 secs of CPU
time per page
Use a PHP Accelerator (bytecode cache) e.g. eAccelerator, Zend, Alternative PHP Cache
Application profiling
Get a faster CPU
Database swamped?
Use mysqladmin to figure out how many transactions per second you are using
How many transactions per second can a database process? fully cached: lots requiring a disk access: 100? 200?
Solutions: optimize expensive queries add indexes on tables enlarge server's query cache / tune server reduce database writes
Drupal-specific optimizations
Some improvements you can make in Drupal: Turn on page caching Stylesheet optimization Prune the sessions table/make sessions shorter
Reduce time before garbage collection (cron) Prune error reporting logs (watchdog table) Automatic throttling
What next?
I've done all that. What else can I do? Separate database server Load balancer and additional servers Database replication
top related