Programming

systemd’s logo (C) https://brand.systemd.io/ Do you have some kind of application that should only be executed when the user’s CPU has a certain feature? Or maybe your application has horrible performance unless some certain instructions are available? As you might know already, the Linux kernel exposes this information via /proc/cpuinfo: processor : 15 vendor_id : AuthenticAMD cpu family : 23 model : 96 model name : AMD Ryzen 7 PRO 4750U with Radeon Graphics ... flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd _apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce to poext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 hw_pstate ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xge tbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif umip rdpid overflow_recov succor smca Where does this data come from? One source of information is the cpuid instruction. On the x86 architecture systemd starting from v248 is now able to start or stop an unit based on the features exposed by the CPUID instruction. Enter ConditionCPUFeature. On CPUs that do not have the CPUID instruction i.e. ARM CPUs, it is assumed that the CPU implements no features and thus any potential CPUFeature conditions will fail. ...

Recently I ran into a surprising ZSH performance bottleneck while editing my .zshrc. Because it gets loaded every time a new shell comes up, I have noticed the issue pretty fast. I quickly started digging into the problem. Apparently, this surprising behavior concerns appending new elements to an array. I did not have a huge file that I was trying to read, only about 6000 elements or so. But still, it had a significant impact on how fast the Z shell was able to start up. ...

While working with Puppet recently I have noticed that there is some funny business going on with the rules of parameter naming. The Puppet’s documentation states: Parameter names begin with a dollar sign prefix ($). The parameter name after the prefix: Must begin with a lowercase letter. Can include lowercase letters. Can include digits. Can include underscores. Let’s see if this is true. Tried applying this manifest with Puppet 5.5.10 which is available on Ubuntu Focal Fossa (20.04): ...

Main logo of the website Hello everyone! I want to do a write-up of another failed website that I have tried to make in order to earn some side income. The attempt has been a bit different from the previous one - I have built a minimal viable product in this case. I have done that so that I could try out my hypothesis about the feasibility and viability a bit more but, of course, it took more time. But I have tried to take every shortcut that I could have thought of. ...

I have recently run into this one small issue while using the FluentValidation library on enums in C#. In particular, there can be problems when using IsEmpty() on enums. Now I’m not an expert on C# but I will try my best to explain this issue. Let’s first start with a recap on how enums work. They allow you to associate some kind of numerical values with names, in essence. If you do not specify any explicit value for an enum value, the compiler automatically takes the numerical value of the previous enum that went in the same type and adds one to it. In the case of the non-existence of the previous value, it starts at 0. ...

In the Cloud-based computing world, a relatively popular free and open-source software product called Prometheus exists which lets you monitor and observe other things. One of the components of its user interface lets you execute ad-hoc queries on the data that it has and see their results - not just in a table but also in a graphical way as well. For example, this is a query time() which plots the current time using two dimensions: ...

Recently I have read a quite popular book called “The Design of Everyday Things”. I feel that with software slowly taking over more and more parts of the world, we could say that it also became an everyday thing and that we should design it like that. This blog post will be about it. There are certain, general design principles that were explained in that book which we should apply to the process of programming in general. ...

A simple house a.k.a. property Testing software is ubiquitous and people naturally expect it to be a part of any kind of software development process. There are many different kinds of forms it can take: at the most rudimentary level: ad-hoc testing; integration testing; synthetic testing; and many others One of the forms that are quite novel is property-based testing. Essentially, the idea is to check if the software that you’ve produced espouses certain characteristics under inputs which have certain distinctive qualities. It sounds very similar to ordinary unit tests however here the catch is that a random number generator is leveraged in this case. Or, you can think of fuzzing but for ordinary code, not binary interfaces. It lets you run a bunch of tests very quickly and find the edge cases under which your code might not work as expected. ...

Like almost everyone, I also dream about starting my own business so that I could be free from the shackles of someone else and I would be my own boss. Or it could become potentially a source of passive income. As such, I have started reading some literature and sites like Indiehackers to learn about how others start their own software businesses. After all, software is the thing that I am most skilled in and so I ought to connect that with the other things which are involved in having a successful business to start my own software company. ...

Intro Having a monitoring infrastructure is one of the tenets of the DevOps world. And, it seems that Prometheus and all of its extraneous integrations such as Thanos or Uber’s M3DB is taking over that world slowly. They give you a lot of improvements over the old Graphite set-ups such as increased reliability since Prometheus is based on HTTP which uses TCP thus you explicitly know when something goes wrong compared to UDP; it uses a pull based model so you explicitly know when something goes wrong and so on. ...