The story is here: https://engineering.mongodb.com/post/we-replaced-an-ssd-with-storage-class-memory-here-is-what-we-learned

This crispy goodness came out of my oven. There are many great breads out there. Why bother making my own?

This bread was made with only three ingredients: grain, water and salt. I do not use commercial flour. I buy local grain and grind it in a small mill that sits on my countertop. I do not use commercial yeast. I grow my own using freshly milled flour and water (and bacteria in my home). I do not sift the flour and my mill does not discard any part of the grain during milling. …

When I ask my colleagues why mmap is faster than system calls, the answer is inevitably “system call overhead”: the cost of crossing the boundary between the user space and the kernel. It turns out that this overhead is more nuanced than I used to think, so let’s look under the hood to understand the performance differences.

Background (skip if you are OS expert):

System calls. A system call is a special function that lets you cross protection domains. When a program executes in user mode (an unprivileged protection domain) it is not allowed to do things that are permitted for the code executing in the kernel mode (a privileged protection domain). For example, a program running in user space typically cannot read files without help from the kernel. When a user program asks a service from an operating system, the system protects itself from malicious or buggy programs via system calls. A system call executes a special hardware instruction, often called “trap”, that transfers control into the kernel. …

I’ve been hearing about ketosis for many years; first by way of the (in)famous Atkins diet, and then via other avenues. Even though I did not read about it deeply, I stayed largely skeptical. Like many others, I thought that getting into ketosis required restricting one’s diet to butter layered with cream over huge pieces of steak. To me, that was decidedly unappetizing. Then recently, a few months after I started following my “Japanese Diet”, which involved no steaks or cream, but lots of fish, green vegetables and (yes) butter, I accidently stumbled into ketosis. I realized two important things: (1) I LOVE how it makes me feel, (2) I could get into it WITHOUT huge dietary restrictions that most people think it requires. …

Ten months on “Japanese diet” improved diversity of my microbiome (from 75th percentile to 84th according to Ubiome), reduced my weight by 5kg, and generated lots of questions from my friends. This post is dedicated to answering the most common question: What do you actually eat?

I write “Japanese diet” in quotes, because, counterintuitively, it involves few Japanese recipes. Instead it follows the principles that I think are key to how Japanese people eat: diversity of vegetables, beans and legumes, lots of fish, few refined carbs and sweets. (My previous post explains this in detail).

To illustrate what my family eats, I am going to describe several concrete dinners and breakfasts, with pictures and recipes. This post will focus on breakfast. …

On July 18, 2018 the European Commission issued Google an unprecedented fine of €4.34 billion for allegedly illegal competitive practices. In its statement it said:

“ Our case is about three types of restrictions that Google has imposed on Android device manufacturers and network operators to ensure that traffic on Android devices goes to the Google search engine.”

Wait, isn’t Android open source? (Yes.) If so, can’t anybody download the code and run it on their device in any way they want? (Yes.) Then how could Google impose any restrictions? …

My recent interest in human microbiome led me to explore the traditional Japanese diet. Not the weight loss diet, but their way of eating. In this post I will share the few bits that I learned about these fascinating subjects.

Human microbiome is the community of microbes that live inside us. Of particular interest is the microbiome of our guts. Researchers have linked the composition of the gut microbiome to various diseases, obesity, and even personality traits. Furthermore, using germ-free mice (special mice cultivated in the lab to have absolutely zero microbes in their guts), the researchers were able to demonstrate interesting causal effects. For example, if you inject the microbiome of an obese person into a germ-free mouse, the mouse gets fat. If you inject the microbiome of a skinny person, the mouse gets skinny. There are even documented human cases, such as this one (pg. …

When several threads run concurrently on the cores of a multicore processor they may need to share data. In a write-sharing mode, where one thread reads and another one writes, data needs to be protected in order to avoid race conditions, which may result in lost or corrupted data. This excellent article by Hans Boehm and Sarita Adve goes in depth about all the bad things that can happen if you don’t properly synchronize your accesses to shared variables.

Most programmers are aware that synchronization, typically performed with atomic instructions wrapped in locks or mutexes, is costly. Few, however, realize that even if shared variables are left unprotected, accessing them can become extremely costly on modern multicore machines. …