Posts Tagged ‘buckets’

Optimizing Linux TCP/IP Networking to increase Linux Servers Performance

Tuesday, April 8th, 2008

Reading Time: 3minutes


Some time ago I thought of ways to optimize my Linux Servers network performance.

Even though there are plenty of nice articles on the topic on how to better optimize Linux server performance by tunning up the kernel sysctl (variables).

Many of the articles I found was not structed in enough understandable way so I decided togoogle around and  found few interesting websites which gives a good overview on how one can speed up a bit and decrease overall server loads by simply tuning few basic kernel sysctl variables.

Below article is a product of my research on the topic on how to increase my GNU / Linux servers performance which are mostly running LAMP (Linux / Apache / MySQL / PHP) together with Qmail mail servers.

The article is focusing on Networking as networking is usual bottleneck for performance.
Below are the variables I found useful for optimizing the Linux kernel Network stack.

Implementing the variables might reduce your server load or if not decrease server load times and CPU utilization, they would at lease increase thoroughput so more users will be able to access your servers with (hopefully) less interruptions.
That of course would save you some Hardware costs and raise up your Servers efficiency.

Here are the variables themselves and some good example:

# = 0 ( Turn off IP Forwarding )

net.ipv4.conf.default.rp_filter = 1

# ( Control Source route verification )
net.ipv4.conf.default.accept_redirects = 0

# ( Disable ICMP redirects )
net.ipv4.conf.all.accept_redirects = 0 ( same as above )
net.ipv4.conf.default.accept_source_route = 0

# ( Disable IP source routing )
net.ipv4.conf.all.accept_source_route = 0
( - || - )net.ipv4.tcp_fin_timeout = 40

# ( Decrease FIN timeout ) - Useful on busy/high load
serversnet.ipv4.tcp_keepalive_time = 4000 ( keepalive tcp timeout )
net.core.rmem_default = 786426 - Receive memory stack size ( a good idea to increase it if your server receives big files )
net.ipv4.tcp_rmem = "4096 87380 4194304"
net.core.wmem_default = 8388608 ( Reserved Memory per connection )
net.core.wmem_max = 8388608
net.core.optmem_max = 40960
( maximum amount of option memory buffers )

# like a homework investigate by yourself what the variables below stand for :)
net.ipv4.tcp_max_tw_buckets = 360000
net.ipv4.tcp_reordering = 5
net.core.hot_list_length = 256
net.core.netdev_max_backlog = 1024


# Below are newly added experimental
#net.core.rmem_max = 16777216
#net.core.wmem_max = 16777216
##kernel.msgmni = 1024
##kernel.sem = 250 256000 32 1024


Also a good sysctl.conf file which one might want to substitite or use as a skele for some productive server is ready for download here

Even if you can't reap out great CPU reduction benefits from integrating above values or similar ones, your overall LAMP performance to end customers should increase – at some occasions dramatically, at others little bit but still noticable.

If you're unsure on exact kernel variable values to use check yourself what should be the best values that fits you according to your server Hardware – usually this is done by experimenting and reading the kernel documentation as provided for each one of uplisted variables.

Above sysctl.conf is natively created to run on Debian and on other distributions like CentOS, Fedora Slackware some values might either require slight modifications.

Hope this helps and gives you some idea of how network optimization in Linux is usually done. Happy (hacking) tweakening !

Test your web browser compatability with Acid3 test

Wednesday, January 25th, 2012

Reading Time: 2minutes

Acid3 Test is a group of browser compitability tests. Acid3 test is a good indicator on how Web ready is your browser.

Acidtest is part of the web standards project. Latest Firefox 9.0.1 passes the test on 100% (100/100).
I've tried it with Epiphany and it scored only 67/100, still I'm using Epiphany on daily basis and I'm quite happy with it.
Acid3 browser compitability Test Firefox 9.0.1
The tests involved are testing browser for:

  • DOM
  • DOM2
  • Checks on HTML tables and forms browser rendering
  • SVG compitability testing
  • DOM1 and DOM2 compitability
  • Various ECMA Script Javascript compitability tests
  • Unicode (UTF-16 and UTF-8) browser compitability
  • XHML, SMIL, CSS, HTML compitability
  • Content-type image/png, text plain etc.

Acid3 browser test fail
The Acid3 test is written itself in Javascript. It consists of 6 testing "stages" (buckets) upon which the browser tested is evaluated.
Each of the test is represented visually by a rectangle. If the a test stage is passed you see a new rectangle appearing in the tested browser.
In wikipedia, there is a thorough list with web browsers by type and engine and the level of support for the Acid3 test.
The test is of great use if you're web developer.