atomics & fences

Acquire
    cannot move anything up beyond an acquire

Release
    cannot move anything down beyond a release

Note
    acquire/release cannot be reordered with respect to each other
 
What does this mean?

instructions can be reordered from before an acquire to after an acquire
instructions can be reordered from after a release to before a release
acquire cannot be reordered before or after a release
release cannot be reordered before or after an acquire

std::atomic
    read = load_acquire --> read the value == acquire the value
    write = store_release --> write the value == release the value

Sequential Consistency
Transitivity / Causality
Total Store Order

using /proc/irq/#/smp_affinity to shield cpus from IRQs

IRQs (interrupt requests) are a request for service at a hardware level from the kernel.

When an IRQ arrives the kernel switches to interrupt context and loads the ISR (interrupt service routine) for the IRQ number which will process the interrupt.

IRQs have an affinity mask which defines which CPUs the ISR can run on. This is defined in /proc/irq/#/smp_affinity

The irqbalance service distributes IRQs across the processors in their associated affinity masks on a multiprocessor system. It uses /proc/irq/#/smp_affinity if it exists, or otherwise falls back to /proc/irq/default_smp_affinity/

The affinity mask in /proc/irq/#/smp_affinity and /proc/irq/default_smp_affinity is a 32-bit hex bitmask of CPUs.
    eg: ffffffff means all 32 CPUs 0-31
If there are more than 32 cores, we build up multiple comma separated 32-bit hex masks.
    eg: ffffffff,00000000 means CPUs 32-63

The irqbalance service uses the environment variable IRQBALANCE_BANNED_CPUS to tell it which CPUs it can't use for ISRs and IRQBALANCE_BANNED_INTERRUPTS to tell it which IRQs to ignore,

IRQBALANCE_BANNED_CPUS follows the same comma separated 32-bit hex format as /proc/irq/#/smp_affinity
IRQBALANCE_BANNED_INTERRUPTS is a space separated list of integer IRQs.

We can shield some CPUs from being interrupted in order to dedicate them to our own tasks.

We can also pin a network data consuming process onto a certain CPU and set the associated NIC (network interface controller) IRQs affinity mask to the same CPU so that they can share cache lines.

Create angular app and express server / mongodb with yeoman

install (or update) yeoman
npm install -g yo 

npm update -g yo

install (or update) yeoman angular fullstack generator (angular frontend / express server)
npm install -g generator-angular-fullstack

npm update -g generator-angular-fullstack

create angular app
yo angular-fullstack [name] // creates ng-app="nameApp", if blank uses curdir

I chose yes to add bootstrap, no for scss authoring, angular-resource (ngResource) and angular-route (ngRoute) and yes for mongoose/mongodb

add angular-bootstrap (angular directives for twitter bootstrap)
bower install angular-bootstrap --save

run karma tests
grunt karma

get rid of the missing file warning by commenting out the following line from the files array:
    'test/mock/**/*.js',

grab phantom.js for headless testing
http://phantomjs.org/download.html

configure karma to run Phantom.js instead of Chrome to
in karma.conf.js change browsers array to PhantomJS

run karma tests again to validate there are no warnings, and we're running through Phantom.js
grunt karma

serve angular app

grunt server


Github page for the angular-fullstack generator here:

https://github.com/DaftMonk/generator-angular-fullstack

Great blog entry with more details here:

http://www.sitepoint.com/kickstart-your-angularjs-development-with-yeoman-grunt-and-bower/

MongoDb on Fedora 19

Install and start server

yum install mongodb-server
systemctl start mongod

systemctl enable mongod

systemctl status mongod

Install client and verify it can connect to the server

yum install mongodb

mongo

You should now be in the mongo shell - test you can save and retrieve an object

db.test.save( { a: 1 } )

db.test.find()

Should display something like this:

{ "_id" : ObjectId("525f2fb01ec8e4af43c529c0"), "a" : 1 }

hello world app with node.js and express.js

requires node and express to be installed (see here for instructions)

go to the root directory where your hello world app will be created
$ cd ~/src/web

create an express app called 'helloWorld' (and use the less css tool)
$ express helloWorld -c less

obtain  the required dependencies and install

$ cd helloWorld

$ npm install

run the server

$ npm start # npm calls 'node app'

add nodemon to our devDependencies so the server gets restarted automatically during development

$ vim package.json  

add the following

"devDependencies": {

    "nodemon": "*"

}

change the scripts / start value:    

"start": "nodemon app.js"

download dependency nodemon

$ npm install

start the server via nodemon

$ npm start

node.js / express.js / yeoman / angular installation on Fedora 19

download the prebuilt binary:
http://nodejs.org/dist/v0.10.20/node-v0.10.20-linux-x64.tar.gz

download and build from source
cd /tmp
wget http://nodejs.org/dist/v0.10.20/node-v0.10.20.tar.gz
tar -xf node-v0.10.20-linux-x64.tar.gz
cd node-v0.10.20-linux-x64/

configure, build and install
export PREFIX=/usr/local # or whatever your prefix is
./configure --prefix=$PREFIX
export LINK=g++ # only required if you're building on NFS
make
make install

clean up temporary files
rm -rf /tmp/node-v0.10.20-linux-x64*

add node to your path
export PATH=$PREFIX/bin:$PATH

display node and npm versions
node --version
v0.10.20
npm --version
1.3.11

install express.js
npm install -g express

display express version
express --version
3.4.0

install yeoman
npm install -g yo

install yeoman angular generator
npm install -g generator-angular

create angular app
yo angular app-name

serve angular app
grunt server