Muayyad Alsadi muayyad-alsadi

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

Each of these commands will run an ad hoc http static server in your current (or specified) directory, available at http://localhost:8000. Use this power wisely.

Discussion on reddit.

Python 2.x

$ python -m SimpleHTTPServer 8000

	#!/usr/bin/env python
	# http://www.rabbitmq.com/tutorials/tutorial-two-python.html
	import pika
	import sys

	connection = pika.BlockingConnection(pika.ConnectionParameters(
	host='localhost'))
	channel = connection.channel()

	message = ' '.join(sys.argv[1:]) or "Hello World!"

	#!/bin/bash
	# ssh-multi
	# D.Kovalov
	# Based on http://linuxpixies.blogspot.jp/2011/06/tmux-copy-mode-and-how-to-control.html

	# a script to ssh multiple servers over multiple tmux panes


	starttmux() {
	if [ -z "$HOSTS" ]; then

	#!/bin/sh

	#----
	# bootstrap fedora21

	#release=$(cat /etc/fedora-release \| awk '/^Fedora/ {print $3}')
	#arch=$(arch)
	release=21
	arch=x86_64
	ROOTFS=/var/lib/libvirt/lxc/fedora$release-$arch

	#!/bin/bash
	#####################################################
	# Name: Bash CheatSheet for Mac OSX
	#
	# A little overlook of the Bash basics
	#
	# Usage:
	#
	# Author: J. Le Coupanec
	# Date: 2014/11/04

	// sending to sender-client only
	socket.emit('message', "this is a test");

	// sending to all clients, include sender
	io.emit('message', "this is a test");

	// sending to all clients except sender
	socket.broadcast.emit('message', "this is a test");

	// sending to all clients in 'game' room(channel) except sender

	# Example ssh config file. Usually located in ~/.ssh/config (user) or /etc/ssh/ssh_config (system)
	# This works on both linux and MacOS

	# Basic ssh commands converted to ssh/config file format



	# Simplest format
	# Run with: "ssh blog" => (equivalent to: "ssh [email protected]" and "ssh -i ~/.ssh/id_rsa -p 22 [email protected]")
	Host blog

	#Install the relevant packages
	dnf install -y ostree rpm-ostree git python rpm-ostree-toolbox libgsystem;

	#checkout the build scripts
	git clone https://github.com/CentOS/sig-atomic-buildscripts;
	cd sig-atomic-buildscripts
	git checkout downstream

	# create and initialize repo directory
	mkdir -p /srv/rpm-ostree/repo

	#!/bin/sh

	command -v apktool >/dev/null 2>&1 \|\| { echo >&2 "I require apktool but it's not installed. Aborting."; exit 1; }
	command -v keytool >/dev/null 2>&1 \|\| { echo >&2 "I require keytool but it's not installed. Aborting."; exit 1; }
	command -v jarsigner >/dev/null 2>&1 \|\| { echo >&2 "I require jarsigner but it's not installed. Aborting."; exit 1; }

	TMPDIR=`mktemp -d 2>/dev/null \|\| mktemp -d -t 'apkdebug'`
	APK=$1
	DEBUG_APK="${APK%.*}.debug.apk"
	if [ -f $APK ]; then