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Quick Tips for Fast Code on the JVM

I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.

This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea

Firefox bullshit removal

Updated: Just use qutebrowser (and disable javascript). The web is done for.

	/*
	*
	* Golang badger db using GOB to serialize object data into badger fields
	*
	* Golang has its very own serializer / deserializer - Go Object (gob) so why not use it where data passed is entirely within a Go
	* application ?
	*
	* JSON or some other text based solution could be used but gob might be faster.
	*
	* A gob encoder accepts the type bytes.Buffer to encode data to, so to write this to Badger, which accepts the type byte

	#include <stdio.h>
	#include <stdlib.h>
	#include <stdint.h>
	#ifdef _MSC_VER
	#include <intrin.h> /* for rdtscp and clflush */
	#pragma optimize("gt",on)
	#else
	#include <x86intrin.h> /* for rdtscp and clflush */
	#endif

	ColorBackground=#28282a2a3636
	ColorForeground=#f8f8f8f8f2f2
	ColorSelection=#363639394848
	ColorBold=#f4f47676c3c3
	ColorCursor=#5050fafa7b7b
	TabActivityColor=#5050fafa7b7b
	ColorPalette=#000000000000;#9a9a40404646;#90907979b3b3;#929298986363;#3d3d98985a5a;#9a9a53538282;#3a3a4d4d5b5b;#8bfc8bfc8ccc;#4d4d4d4d4d4d;#ffff55555555;#cacaa9a9fafa;#f1f1fafa8c8c;#5050fafa7b7b;#ffff7979c6c6;#8b8be9e9fdfd;#f8f8f8f8f2f2
	ColorSelectionUseDefault=FALSE
	ColorBoldUseDefault=FALSE

	import mailbox
	import csv

	writer = csv.writer(open("mbox-output.csv", "wb"))

	for message in mailbox.mbox('file.mbox/mbox'):
	writer.writerow([message['message-id'], message['subject'], message['from']])

	#!/bin/bash

	# Install prerequisites
	yum install -y gcc openssl-devel libyaml-devel libffi-devel readline-devel zlib-devel gdbm-devel ncurses-devel ruby-devel gcc-c++ jq git

	# Import key
	curl -sSL https://rvm.io/mpapis.asc \| gpg2 --import -

	# Install RVM
	curl -sSL https://get.rvm.io \| bash -s stable --ruby

	#!/bin/bash
	#
	# steps taken verbatim from:
	# http://docs.aws.amazon.com/AmazonECS/latest/developerguide/docker-basics.html#install_docker
	#
	sudo yum update -y
	sudo yum install -y docker
	sudo service docker start
	sudo usermod -a -G docker ec2-user
	# log out and log in to pickup the added group

	# copied from http://gbayer.com/development/moving-files-from-one-git-repository-to-another-preserving-history/
	git clone <git repository A url> # clone source repository
	cd <git repository A directory>
	git remote rm origin # to make sure it doesn't affect the original repository
	git filter-branch --subdirectory-filter <directory 1> -- --all # remove all files other than the ones needed
	mkdir <directory 1> # move them into another directory where they will be stored in the destination repository (if needed)
	mv * <directory 1>
	git add .
	git commit

	#!/bin/bash -e

	echo '
	PATH=$HOME/go/bin:$PATH
	export GOPATH=$HOME
	export CDPATH=.:$HOME/src/golang.org/x:$HOME/go/src:$HOME/src/github.com:$HOME/src/github.com/nf:$HOME/src/github.com/adg
	export EDITOR=vim
	' >> ~/.profile

	sudo apt-get update