Displaying Linux Memory

Memory management is hard, but RAM management may be even harder.

Most people know the vague overall concept of how memory usage is displayed within Linux. You have your total memory which is everything inside the box; then there is used and free which is what the system is or is not using respectively. Some people might know that not all used is used and some of it actually is free.  It can be very confusing to understand, even for a someone who maintains procps (the package that contains top and free, two programs that display memory usage).

So, how does the memory display work?

Read more Displaying Linux Memory

pidof lost a shell

pidof is a program that reports the PID of a process that has the given command line. It has an option x which means “scripts too”. The idea behind this is if you have a shell script it will find it. Recently there was an issue raised saying pidof was not finding a shell script. Trying it out, pidof indeed could not find the sample script but found other scripts, what was going on?

Read more pidof lost a shell

Forking processes and Gtk2

I made a change recently on the gjay program. gjay is a gtk program that basically analyzes your music and makes playlists. There is a gui frontend and a analyzer back-end and they communicate through a pipe.

One really useful debugging option gtk has is to make warnings fatal, so when gtk finds one it crashes at that point and you can use gdb to trap it. The flag is –g-fatal-warnings.  I have been updating gjay and initially it didn’t have this option, so I needed to add the gtk options, which is a simple one-liner.
Read more Forking processes and Gtk2

ps standards and locales

I looked at two interesting issues today around the ps program in the procps project. One had a solution and the other I’m puzzled about.

ps User-defined Format

Issue #9 was quite the puzzle. The output of ps changed depending if a different option had a hyphen before it or not.

First, the expected output

$ ps p $$ -o pid=pid,comm=comm
 pid comm
31612 bash

Next, the unusual output.

$ ps -p $$ -o pid=pid,comm=comm

Read more ps standards and locales

WordPress 4.3 getting slow you might need an update

I recently received Debian bug report #798350 where the user had a problem with wordpress. After upgrading to version 4.3, the webservers performance degrades over time.  The problem is also reported at the wordpress site with bug WordPress ticket 33423 including the fix.

I have backported the relevant changeset and uploaded Debian wordpress package 4.3+dfsg-2 which only contains this changeset.  For a lot of people, including myself, you probably won’t hit this bug but if it impacts you, then try this update.