jboner

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

hellerbarde

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

rgreenjr

-- show running queries (pre 9.2)
SELECT procpid, age(clock_timestamp(), query_start), usename, current_query 
FROM pg_stat_activity 
WHERE current_query != '<IDLE>' AND current_query NOT ILIKE '%pg_stat_activity%' 
ORDER BY query_start desc;

-- show running queries (9.2)
SELECT pid, age(clock_timestamp(), query_start), usename, query 
FROM pg_stat_activity 
WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%' 

ryankearney

<script language="JavaScript" type="text/javascript">
// Comcast Cable Communications, LLC Proprietary. Copyright 2012.
// Intended use is to display browser notifications for critical and time sensitive alerts.
var SYS_URL='/e8f6b078-0f35-11de-85c5-efc5ef23aa1f/aupm/notify.do';
// var image_url='http://servicealerts.comcast.net:8080/images/mt';
var image_url='http://xfinity.comcast.net/constantguard/BotAssistance/notice/images';
var headertext1='<strong>Comcast Courtesy Notice</strong>';
var textline1='You have reached 90% of your <b>monthly data usage allowance</b>.';
var textline2='Please sign in for more information and to remove this alert.';
var acknowledgebutton='<a href=\"#\" onClick="document.location.href=\''+SYS_URL+'?dispatch=redirect&redirectName=login&paramName=bmUid\'" title="Sign in to acknowledge" style="color: #FFFFFF;"><img alt="Sign in to acknowledge" src="'+image_url+'/mt_signin.png"/></a>';

rnewson

# Bind SSL port with PFS-enabling cipher suite
bind :443 ssl crt path_to_certificate no-tls-tickets ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-GCM-SHA384:AES128-SHA256:AES128-SHA:AES256-SHA256:AES256-SHA:!MD5:!aNULL:!DH:!RC4

# Distinguish between secure and insecure requests
acl secure dst_port eq 443

# Mark all cookies as secure if sent over SSL
rsprep ^Set-Cookie:\ (.*) Set-Cookie:\ \1;\ Secure if secure

# Add the HSTS header with a 1 year max-age

jasonruyle

#Country ban with UFW#

Grab your different country ip addresses and save as Linux IPTables

http://www.ip2location.com/free/visitor-blocker

##Add country## Run the following command

JamesMGreene

Initialize

gitflow	git
git flow init	git init
	git commit --allow-empty -m "Initial commit"
	git checkout -b develop master

Connect to the remote repository

tmilos

Modified Preorder Tree Traversal

Hierarchical data metrics that allows fast read operations on tree like structures.

Based on Left and Right fields that are set during tree traversal. When entered into node value is set to it's Left, when exiting node value is set to it's Right.

Sample implementation

ipbastola

Safest way to clean up boot partition - Ubuntu 14.04LTS-x64, Ubuntu 16.04LTS-x64

Reference

Case I: if /boot is not 100% full and apt is working

1. Check the current kernel version

$ uname -r 

joseluisq

How to enable the MySQL/MariaDB general query logs

1. Enter to MySQL/MariaDB server command-line tool (change root with your username and password):

mysql -u root -proot

2. Set the general log file path:

SET GLOBAL general_log_file='/var/log/mysql/mycustom.log';