Make Linux faster and lighter<3>

Boost your network

You've tweaked your router, optimised your server and replaced all your broadband filters in your house - and you still have a slow connection. Before you make an angry phone call to your ISP, there's a possibility that the client machine may be the bottleneck. With just a few of these tweaks you can improve your connections, or at the very least eliminate your client machine as the single point of failure.

Use hostname 'localhost'

This doesn't cause a drastic improvement on its own, but in conjunction with the other network tricks here can improve your local machine's network performance. Simply open /etc/hosts in a text editor with root permissions and change the top two lines to:

127.0.0.1 localhost yourhost
127.0.1.1 yourhost

where yourhost is the name of the machine (ie bobdesktop). Ensure you keep a backup of your /etc/hosts file, as not all distros are compatible with this!

Optimise TCP settings

Distros come preconfigured for "average" internet users, but in a world of 3G, dial-up and ADSL there is no such thing as an average user. Now edit /etc/sysctl.conf as root and append the following:

net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_sack = 1

(This may take some trial and error, so keep a backup of the files you edit.) The top line removes timestamps and so relieves all incoming and outgoing packets of a 12k overhead. The bottom line enables selective acknowledgements, which means fewer checks are initiated on each packet so they are delivered quicker. We don't recommend the latter tweak for dial-up connections as this increases the number of packets which need to be resent.

Metrics and backlogs

You can further optimise your TCP settings by appending the following lines to the same text file:

net.ipv4.tcp_no_metrics_save = 1
net.core.netdev_max_backlog = 2500

The top line speeds up connections by ensuring that TCP metrics are not saved for each individual packet. The second line dictates the backlog of packets allowed. To give an idea of the scale of the figure you should use for your backlog, around 2,000 is recommended for wireless or older Ethernet connections, and around 5,000 for a 1GB Ethernet cable to broadband connection. On the other hand, this figure can rise up to 30,000 for an expensive 10GB Ethernet cable. The slower the connection, the lower your backlog should be, as the aim of this tweak is to clear outstanding packets as soon as possible in order to boost connection speeds.

TCP window scaling

The TCP window settings define the minimum and maximum size of packets we can send and recieve. Dial-up users will see a speed boost with smaller packet sizes while broadband users will see a speed boost with larger packet sizes. Edit /etc/sysctl.conf as root, and append this:

net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_wmem = 10240 87380 16777216
net.ipv4.tcp_rmem = 10240 87380 16777216
net.ipv4.tcp_mem = 16777216 16777216 16777216
net.core.rmem_max = 16777216
net.core wmem_max = 16777216

Those figures are optimised for a 2Mbps connection on Sky broadband over a wireless connection, but the packet size recommendation for any given connection is usually maximum bandwidth divided by latency. You can find these figures by heading to www.speedtest.net , and you can also analyse how your changes are affecting your connection via www.speedguide.net:8080 .

www.speedguide.net can give you an indication of which values and tweaks will improve your network connection.

 

Faster Firefox

Continuing with the networking theme, you can optimise much more than just your TCP settings. Mozilla Firefox has a raft of options cunningly hidden from users that can untap the browser's potential...

Disable IPv6 (again!)

With this tweak we will simply amend an existing value. Type the following into the search bar: network.dns.disableIPv6

You shouldn't have to type out the whole thing, as the listings change dynamically as you're typing. Simply double-click on the entry to change the default value of "False" to "True".

Render pages faster

Create a new integer value in about:config named content.notify.backoffcount and set the value to 5 so that Firefox won't wait for the entire page to download before rendering. You can also create a value with the name nglayout.initialpaint.delay and set the value to zero . This ensures that Firefox doesn't wait for the page layout information to be fully downloaded before rendering.

Optimise your history

If you reduce the amount of web history that Firefox stores, it will load faster and also save you some disk space. Type the following in the search bar: browser.history and change browser.history_expires_days and browser.history_expires_min to zero . You can also use low numbers if you want to keep some browser history.

More TCP tweaks

Change the network.http.pipelining and network.http.proxy.pipelining values to "True" and then set network.http.pipelining.maxrequests to 8 instead of 4 . These tweaks boost performance for broadband users as we use a TCP technique known as pipelining, which allows Firefox to make multiple requests on a single connection.

Any mistakes here could break Firefox, so once you've made a backup and a vow of honour you can unleash the power hidden in your browser.

Speed up menus

Start by typing about:config and accepting the warning that comes up (you will need to do this for all these Firefox tips). The listing you see is much like the Firefox equivalent of the Windows registry, which means that though this is a very powerful way to tweak your browser you can cause serious stability problems if you get it wrong.

We can make our Firefox menus load faster by adding our own value to the listing. Right-click anywhere in the listing and then click New > Integer . Use ui.submenuDelay as the name and then set the value to zero . When you restart Firefox you should notice that your menus load noticeably faster, as you have removed the delay for the menu popups.

Voice of the Guru #3

Paul Frields - Fedora project leader

"Here's something I can’t live without: combining the Mutt mail reader with offlineimap. The offlineimap utility synchronises my remote IMAP stores on to my local hard disk, which means my email reading is faster by several orders of magnitude. I can sync my email before I pack for travel, and then while in transit, or waiting at an appointment, I can read email as quick as a flash because it's all stored locally. Mutt makes my mail processing chores incredibly efficient, so I can effectively deal with the thousands of email messages I get every week. When I get back online and run offlineimap again, all the flags are synchronised again and my remote IMAP stores record what I've read."