The curious case of nanosleep vs. hr_sleep
This weekend, I finally got around reading a bookmarked paper that proposes an improved nanosleep:
In the following I document a few notes.
The Papers¶
At page 4 I'm asking …
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On the Costs of Syscalls
It's well known that syscalls are expensive. And that software mitigations against CPU bugs (such as Meltdown) even have made them more expensive. But how expensive are they really? To begin to answer this question I wrote a small micro-benchmark in order to measure the minimal costs of a syscall …
The Rise of Meson
More and more open source projects seem to switch to the Meson build tool, in the last years. In an attempt to quantify this development I looked at the build tools usage by Fedora packages, during the last 14 years.
About Meson¶
Meson is a build tool with good C …
Deploying Full Disk Encryption in the Cloud with Ansible
Deploying a new virtual machine 'in the cloud' is simple enough and fast. As long as one doesn't need to setup an encrypted root filesystem. This article shows how to automate the setup of a Fedora system with an encrypted root filesystem remotely - 'in the cloud' - on e.g. a …
Deploying SSH Host Keys with Digital Ocean Droplets
When deploying a VM in a remote location one might end up in an impossible situation: a VM base image doesn't contain SSH host keys as otherwise the image couldn't be shared between multiple hosts. But if SSH host keys are auto-generated during the first boot one doesn't know their …
NFS VM Cached Read Illustrated
This article illustrates how the virtual memory (VM) subsystem of the Linux kernel is able to cache files that are located on an NFS server.
Environment¶
In this small experiment we just need two Linux machines on a local network, where one …
Check CPU Microcode Version on Linux
Debian recently released a warning advisory regarding a hardware bug in the hyperthreading implementation on certain Skylake/Kaby Lake Intel CPUs. It can be mitigated by a microcode firmware update - at least on some models. This article is about checking a non-Debian system for this issue and verifying if the …
Fedora as Grml replacement
Grml is a Linux Live CD distribution geared towards system administration tasks and other console work. Unfortunately, its development has slowed down in the past years, i.e. the latest stable release is from 2014. In 2017, when dealing with modern hardware, modern features like Btrfs, SELinux etc. this is …
Btrfs requires noatime
Traditionally, UNIX filesystems also maintain the access time (atime) of a file. This is very much an anti-feature because it yields a write operation for each read operation. Which is obviously bad for performance. Since Btrfs is a copy-on-write (COW) filesystem maintaining atimes is even more painful. Thus, a sensible …