Worth the read: Metrics That Matter

There’s a book titled “Measure What Matters”, and it’s fascinating and worth the read. This article from acmqueue with nearly the same title is quite interesting, because it turns some of my previous thinking on it’s head.

Metrics That Matter

Summary: “Speed matters”; Instrument client code to measure user experience; Measure “long-tail” latency at the 95th and 99th percentiles; even minor changes to code or user behavior can effect things; build bench-marking into release testing procedures.

OpenWRT + SafeSearch

I’ve got an OpenWRT router, and here’s how I configured it to enable safesearch on my home network.

uci add dhcp cname
uci set dhcp.@cname[-1].cname="www.google.com"
uci set dhcp.@cname[-1].target="forcesafesearch.google.com"
uci commit dhcp

uci add dhcp cname
uci set dhcp.@cname[-1].cname="www.bing.com"
uci set dhcp.@cname[-1].target="strict.bing.com"
uci commit dhcp

uci add dhcp cname
uci set dhcp.@cname[-1].cname="duckduckgo.com"
uci set dhcp.@cname[-1].target="safe.duckduckgo.com"
uci commit dhcp

for name in www.youtube.com m.youtube.com youtubei.googleapis.com youtube.googleapis.com www.youtube-nocookie.com ; do
    uci add dhcp cname
    uci set dhcp.@cname[-1].cname="$name"
    uci set dhcp.@cname[-1].target="restrict.youtube.com"
    uci commit dhcp

service dnsmasq restart

See the configuration:

grep -A2 cname /etc/config/dhcp

Python: How to reduce memory usage

Useful information for reducing memory usage of Python programs:

  • https://m.habr.com/en/post/458518/
  • https://stackoverflow.com/questions/472000/usage-of-slots

TLDR: Dictionaries use a lot of memory. Possible solutions include using a class and slots, namedtuple, recordclass, cython, or numpy.

Screen brightness: Linux + Lenovo P50

I run Ubuntu on my Lenovo P50, and the backlight keys haven’t ever worked. Here’s how I got it working.

sudo apt install xbacklight

Then I mapped the keys using Settings > Devices > Keyboard and added mappings for the following:

Windows-F5: xbacklight -inc 5 -time 1 -steps 1
Windows-F6: xbacklight -dec 5 -time 0 -steps 1


If you write Linux shell scripts (bash), you should use https://www.shellcheck.net/ to improve the quality of the script.

Code reviews: Benefits and Counterindications

Microsoft has a long article in ACM Queue on what people think they’re getting out of code reviews, what they’re actually getting, as well as a list of benefits a code review tool should provide.

My main takeaways:

  • Requiring two sign-offs is too many for low-risk changes such as renaming internal (not API) methods or local variables — only need one reviewer
  • Tag the files/changes that are at the heart of the change
  • Small reviews get better feedback. More than 20 files, and a code review isn’t going to provide much, if any, value.
  • If code reviews are important, doing reviews should be tracked and rewarded, just like anything else that has value.
  • Reviews tend to focus on: comments about maintainability, documentation, alternative solutions, validation, and API usage
  • Reviews only identify bugs ~15% of the time, so some other form of validation is important
  • A good code review tool can help greatly by recommending reviewers — lightening the burden and getting knowledgeable people involved
  • Show entire file to give reviewers context
  • There’s no one-size-fits-all solution for code reviews — i.e. each team and code base has different needs and different culture.

Lightning Memory Mapped Database

My Ubuntu box decided to update this library today, so I learned about a very fast and cool key-value database. It replaces BerkleyDB on Linux systems and is also used to persist data for Redis, InfluxDB, and has even been adapted for use with SQLite — called SQLightning (20x faster).


LibreOffice Spell Checking on Ubuntu 18.04

Spell checking wasn’t working for me in LibreOffice Writer. I followed the instructions here and got it working:


In writer, I used this menu, and it finally worked:

Tools > Language > For all Text > English (USA)

Convert hiec to jpg

I downloaded some photos from Google Photos, only to find that they were in heic format (https://en.wikipedia.org/wiki/High_Efficiency_Image_File_Format). None of my linux programs know how to open that format — I needed them in jpg format. I found a utility to do the job: https://launchpad.net/~xiota/+archive/ubuntu/stuff-3

sudo add-apt-repository ppa:xiota/stuff-3
sudo apt-get install libheif-tools
for f in *heic ; do heif-convert -q 90 $f ${f%.heic}.jpg ; done