Tuesday, July 27, 2010

Tuning Ubuntu 9.10 Karmic for speed and better internet connectivity

After installing Ubuntu Karmic 9.10, I changed the following tunables

swappiness and vfs_cache_pressure

swappiness --> If we have large RAM, there is probably no use for a swap file and we can decrease the swappiness to a very low value without fear. If the RAM capacity is 512 MB or less than 1 GB RAM, then Ubuntu or any linux uses swap as a swapfile. The default swappiness is normally 60 (but I have seen 40 in case of Fedora 11 after updates). Do not touch the swappiness and cache pressure unless you have atleast 1 GB of RAM

If we decrease swappiness, speed of opening programs feels faster

to get current swappiness of system

sudo sysctl -q vm.swappiness

to change swappiness to value 20, which is low

sudo sysctl -w vm.swappiness=20

to increase the speed of browsing files and folders again and again, we should decrease vfs_cache_pressure. Default vfs_cache_pressure is 100, if we decrease it, kernel virtual machine (vm) caches files more and more

to get current vfs_cache_pressure

sudo sysctl -q vm.vfs_cache_pressure

to set vfs_cache_pressure

sudo sysctl -w vm.vfs_cache_pressure = 50

You can read original tuxradar article about improving speed by clicking this http://tuxradar.com/content/make-linux-faster-and-lighter 

Sometime today morning when browsing irctc and opening some news sites, youtube, Ubuntu took a very very long time. Then I remembered that old debian lenny errata page and followed it and tweaked tcp window scaling settings. If you ever feel that you are not able to visit some sites or browse properly, follow this debian errata

Debian Errata, see buggy routers may cause problem





If you are bored to read the above and continue reading here, what I did, here is what I did after following the above errata page

 Hit the site you are having trouble viewing, if you feel there is problem open terminal and change the system param as follows

sudo sysctl -w net.ipv4.tcp_rmem="4096 65536 65536"


sudo sysctl -w net.ipv4.tcp_wmem="4096 65536 65536"

 If you don't feel the same browsing/network issue you faced before setting these two tunables, then proceed below to make the changes permanent

To make above changes permanent upon reboot(speed increase and net improvements)  

Add these lines to end of /etc/sysctl.conf by editing it (sudo vi etc/sysctl.conf)

#decrease swappiness
#improve file/folder browsing speed
#debian tcp window scaling errata fix
net.ipv4.tcp_rmem=4096 65536 65536
net.ipv4.tcp_wmem=4096 65536 65536

Note: sudo sysctl -p reapplies all the settings from /etc/sysctl.conf and can be used

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