kfirshay

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

kfirshay

#!/bin/sh

while true; do
  value=$( cat /proc/swaps | awk '$4 > 0 {print $4}' | sed s/Used// | awk '$1 > 0 {print $1}' )
  if [ ! -z $value ]
  then
    echo clearing swap...
    sudo /etc/init.d/nginx stop
    sudo swapoff -a
    sudo swapon -a

kfirshay

cd /Library/Ruby/Gems/2.0.0/gems/yajl-ruby-0.8.2/ext/yajl/
# Now we need to replace 'inline void' to 'static void'. This will also create backup of old files.
sed -i '.bak' 's/inline void/static void/g' yajl_ext.h yajl_ext.c
# Now we must rebuild changed extension
make clean all
# After this you should not have any problems with yajl-ruby

kfirshay

send_sqs_message = lambda { |payload, queue|
  queue.send_message("#{payload}:#{Time.now.to_s}")
}

Thread.fork { send_sqs_message.call("our payload", queue) }

kfirshay

module ITunes
  def self.mute_or_unmute(command)
    matching = command.match(/^(un)?mute\s+(itunes|((?:the|my)\s+)?music)$/i)
    is_unmute = matching && matching[1] == "un"
    if matching
      {
        :command => Command.bus({:osx => "tell application \"iTunes\" to set mute to #{ !is_unmute }"}),
        :explanation => "#{ is_unmute ? 'Unmutes' : 'Mutes' } iTunes."
      }
    else