jonathanmarvens

The netfilter hooks in the kernel and where they hook in the packet flow

The figure below calls out

• The netfilter hooks
• The order of table traversal

jonathanmarvens

Stevey's Google Platforms Rant

I was at Amazon for about six and a half years, and now I've been at Google for that long. One thing that struck me immediately about the two companies -- an impression that has been reinforced almost daily -- is that Amazon does everything wrong, and Google does everything right. Sure, it's a sweeping generalization, but a surprisingly accurate one. It's pretty crazy. There are probably a hundred or even two hundred different ways you can compare the two companies, and Google is superior in all but three of them, if I recall correctly. I actually did a spreadsheet at one point but Legal wouldn't let me show it to anyone, even though recruiting loved it.

I mean, just to give you a very brief taste: Amazon's recruiting process is fundamentally flawed by having teams hire for themselves, so their hiring bar is incredibly inconsistent across teams, despite various efforts they've made to level it out. And their operations are a mess; they don't real

jonathanmarvens

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

jonathanmarvens

Why stack grows down

Any running process has several memory regions: code, read-only data, read-write data, et cetera. Some regions, such as code and read-only data, are static and do not change over time. Other regions are dynamic: they can expand and shrink. Usually there are two such regions: dynamic read-write data region, called heap, and a region called stack. Heap holds dynamic memory allocations, and stack is mostly used for keeping function frames.

Both stack and heap can grow. An OS doesn't know in advance whether stack or heap will be used predominantly. Therefore, an OS must layout these two memory regions in a way to guarantee maximum space for both. And here is the solution:

1. Layout static memory regions at the edges of process's virtual memory
2. Put heap and stack on edges too, and let them grow towards each other: one grows up, one grows down

jonathanmarvens

#![warn(rust_2018_idioms)]

#[derive(Debug)]
pub struct StrSplit<'haystack, D> {
    remainder: Option<&'haystack str>,
    delimiter: D,
}

impl<'haystack, D> StrSplit<'haystack, D> {
    pub fn new(haystack: &'haystack str, delimiter: D) -> Self {

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// Copyright (c) 2012 Sutoiku, Inc. (MIT License)
 
// Some algorithms have been ported from Apache OpenOffice:
 
/**************************************************************
 * 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file

jonathanmarvens

# Assuming an Ubuntu Docker image
$ docker run -it <image> /bin/bash

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const mean = (values) => {
  const sum = values.reduce((sum, value) => (sum + value), 0)
  const valuesCount = values.length
  return (sum / valuesCount)
}

jonathanmarvens

To install unbound you can use homebrew

$ brew install unbound ldns

Now we can edit the configuration file of unbound which by default is located in /usr/local/etc/unbound/unbound.conf:

jonathanmarvens

Prevent Double Tap Zoom in React for Rapidly Tapped Buttons

Touch delay is [a thing of the past][td], but accidental zooming is here to ruin your day. Ever tapped a button quickly on iOS and experienced a zoom instead of two taps? You're in the right place.

Before