Aliaksandr Belik aliesbelik

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

tmux shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname

Step by step guide to setting up IDEA to write gatling simulations

Prerequisites:

Have [SBT plugin][sbt-plugin] installed

Begin

[Create a new project][create-project] in IDEA ( File > New Project ...)
- Make sure you select a maven module

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


	FILE SPACING:

	# double space a file
	sed G

	# double space a file which already has blank lines in it. Output file
	# should contain no more than one blank line between lines of text.
	sed '/^$/d;G'

	[alias]
	dt = difftool
	mt = mergetool
	[diff]
	tool = bc3
	[difftool]
	prompt = false
	[difftool "bc3"]
	cmd = \"c:/program files (x86)/beyond compare 3/bcomp.exe\" \"$LOCAL\" \"$REMOTE\"
	[difftool "p4"]

	Latency Comparison Numbers (~2012)
	----------------------------------
	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

	#!/usr/bin/perl
	use strict;
	use warnings;

	print "Processing ${ARGV[0]}, filtering domain ${ARGV[1]}\n";
	open INPUT, ${ARGV[0]} or die $!;
	open OUTPUT, ">${ARGV[0]}.filtered.xml" or die $!;

	my $skip = 0;
	while (my $line = <INPUT>) {

	#!/bin/sh

	TSUNG=/usr/local/tsung/bin/tsung
	CONF=/data/httpd/tsung/etc/test.d.xml
	LOG=/data/httpd/tsung/log

	/usr/bin/screen -d -m $TSUNG -f $CONF -l $LOG start

	#!/bin/bash
	#
	# git-mv-with-history -- move/rename file or folder, with history.
	#
	# Moving a file in git doesn't track history, so the purpose of this
	# utility is best explained from the kernel wiki:
	#
	# Git has a rename command git mv, but that is just for convenience.
	# The effect is indistinguishable from removing the file and adding another
	# with different name and the same content.