Boniface Kabaso boniface

Safest way to clean up boot partition - Ubuntu 14.04LTS-x64

Case I: if /boot is not 100% full and apt is working

1. Check the current kernel version

$ uname -r

Sample config for 2 million web socket connection

    sysctl -w fs.file-max=12000500
    sysctl -w fs.nr_open=20000500
    # Set the maximum number of open file descriptors
    ulimit -n 20000000

    # Set the memory size for TCP with minimum, default and maximum thresholds 
 sysctl -w net.ipv4.tcp_mem='10000000 10000000 10000000'

Advanced Functional Programming with Scala - Notes

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

	# maximum capability of system
	user@ubuntu:~$ cat /proc/sys/fs/file-max
	708444

	# available limit
	user@ubuntu:~$ ulimit -n
	1024

	# To increase the available limit to say 200000
	user@ubuntu:~$ sudo vim /etc/sysctl.conf

	import java.util.Random;

	/**
	*
	* @author Vijini
	*/

	//Main class
	public class SimpleDemoGA {

	Latency Comparison Numbers
	--------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD

	# Tweaked from http://tomislavsantek.iz.hr/2011/03/moving-mysql-databases-to-ramdisk-in-ubuntu-linux

	# Log in as root
	# Mount ramdisk folder in RAM
	mkdir /tmp/ramdisk
	mount -t tmpfs -o size=128M tmpfs /tmp/ramdisk/

	# Move MySQL data
	mv /var/lib/mysql /tmp/ramdisk/mysql
	ln -s /tmp/ramdisk/mysql/ /var/lib/mysql