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

santa4nt

from scapy.all import *


# change this to your test machine's MAC address
SELF_MAC = '00:0c:29:67:22:c2'

BCAST_MAC = 'ff:ff:ff:ff:ff:ff'


# this will send a PROBE ARP request packet to the supplied IP address argument

mzabriskie

If you're like me you have a dir like ~/Workspace/Github where all your git repos live. I often find myself making a change in a repo, getting side tracked and ending up in another repo, or off doing something else all together. After a while I end up with several repos with modifications. This script helps me pick up where I left off by checking the status of all my repos, instead of having to check each one individually.

Usage:

git-status [directory]

This will run git status on each repo under the directory specified. If called with no directory provided it will default to the current directory.

CMCDragonkai

HTTP Streaming (or Chunked vs Store & Forward)

The standard way of understanding the HTTP protocol is via the request reply pattern. Each HTTP transaction consists of a finitely bounded HTTP request and a finitely bounded HTTP response.

However it's also possible for both parts of an HTTP 1.1 transaction to stream their possibly infinitely bounded data. The advantages is that the sender can send data that is beyond the sender's memory limit, and the receiver can act on

nerdalert

Linux NetFilter, IP Tables and Conntrack Diagrams

IPTABLES TABLES and CHAINS

IPTables has the following 4 built-in tables.

1) Filter Table

Filter is default table for iptables. So, if you don’t define you own table, you’ll be using filter table. Iptables’s filter table has the following built-in chains.

stewartpark

---
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: oom-killer
  namespace: kube-system
  labels:
    k8s-app: oom-killer
spec:
  selector:

leolara

// Package gochannels example of how to close a channel written by several goroutines
package gochannels

import (
	"math/big"
	"sync"
)

// Publisher write sequences of big.Int into a channel
type Publisher struct {

beriberikix

Create system drive

qemu-img create -f qcow2 alpine.qcow2 16G

Install image

Linux

kdrag0n

Moved to pidfd-rs

Moved to pidfd-rs.

aojea

Navigating Linux Network Namespaces and Interfaces

Network namespaces create isolated network stacks, including network devices, IP addresses, routing tables, rules , ... This separation is crucial for containerization.

Network namespaces also contain network devices that can live exactly on one network namespace:

physical network device can live in exactly one network namespace. When a network namespace is freed (i.e., when the last