Year: 2019

Packets-per-second limits in EC2

“Packets-per-second limits in EC2” is an interesting dive into network limits on the Amazon EC2. Even if you aren’t hitting any limits yet, this article provides plenty of useful information, including benchmarking tools and quick reference links for Enhanced Networking.

The conclusion of the article is:

By running these experiments, we determined that each EC2 instance type has a packet-per-second budget. Surprisingly, this budget goes toward the total of incoming and outgoing packets. Even more surprisingly, the same budget gets split between multiple network interfaces, with some additional performance penalty. This last result informs against using multiple network interfaces when tuning the system for higher networking performance.
The maximum budget for m5.metal and m5.24xlarge is 2.2M packets per second. Given that each HTTP transaction takes at least four packets, we can translate this to a maximum of 550k requests per second on the largest m5 instance with Enhanced Networking enabled.

Why software projects take longer than you think – a statistical model

“Why software projects take longer than you think – a statistical model” is an interesting take on the problem of bad estimations in software projects. I’m not that great with math, but even then the article is very interesting. And there is a lot that I agree with.

Here’s a quote for those of you who couldn’t make it through:

Why software tasks always take longer than you think

Assuming this dataset is representative of software development (questionable!), we can infer some more numbers. We have the parameters for the t-distribution, so we can compute the mean time it takes to complete a task, without knowing the σ for that task is.


While the median blowup factor imputed from this fit is 1x (as before), the 99% percentile blowup factor is 32x, but if you go to 99.99% percentile, it’s a whopping 55 million! One (hand wavy) interpretation is that some tasks end up being essentially impossible to do. In fact, these extreme edge cases have such an outsize impact on the mean, that the mean blowup factor of any task ends up being infinite. This is pretty bad news for people trying to hit deadlines!

Intermediate Vim

Intermediate Vim is a nice collection of Vim tips and tricks, which are aimed at somebody who is already familiar with Vim. (There is of course no single definition of what’s advanced, intermediate or introductory, so we’ll leave that argument out.) But the article is well worth the read, even if you already know all of the mentioned commands. A refresher is always welcome.

Fedora 30

Fedora 30 has been released a few days ago. In the long list of changes, the most interesting to me are:

I’ve already upgraded my laptop to this version and everything seems to work as expected. The upgrade from Fedora 29 to Fedora 30 is easy:

# Install all the latest updates
dnf upgrade --refresh

# Install DNF plugin for system upgrades
dnf install dnf-plugin-system-upgrade

# Download all the necessary packages for Fedora 30
dnf system-upgrade download --releasever=30

# Reboot and start the upgrade of packages
dnf system-upgrade reboot

# Cleanup after successful upgrade
dnf system-upgrade clean

If this is not your first upgrade on the machine, it might also be a good idea to cleanup some of the installed packages BEFORE the upgrade, so that the process goes faster, skipping unnecessary downloads and upgrades. Here are a few suggestions:

# List all installed RPMs by size
rpm -qa --queryformat '%{size} %{name}\n' | sort -rn | less

# List all packages from earlier Fedora releases
rpm -qa | grep -i fc28