The division instruction is one of the most expensive instruction in your CPU. Thus optimizing compilers often compile divisions by known constants down to a multiplication followed by a shift. However, in some lucky cases, the compiler does not even need a shift. I call the corresponding divisors ideal. For the math…
Pumpkin is the name I have given to my port of PalmOS running on the x86 architecture. Please refer to this article for basic information on this project. Also look for other articles in the PalmOS…
I've been running QubesOS as my main desktop since 2015. It provides good security, by running applications in different Xen VMs. However, it is also …
This post is the second in a three-part series about Cranelift . In the first post , I described the context around Cranelift and our project to replace its backend code-generation infrastructure, and detailed the instruction-selection problem and how we solve it. The remaining two posts will be deep-dives into some…
Google's gRPC is an RPC system that supports many languages, and is relatively widely used. I think its popularity is due to being used for parts of Docker and Kubernetes. I think gRPC is mostly fine, but it is surprisingly easy to screw up by misconfiguring it. Part of that is because RPC systems are challenging to…
Quick edit: While I work on a proper update, I'll note here that several posters on reddit and hackernews have pointed out ways to bring the total size of the program down to 105 bytes while still printing the full "Hello, world!" Much credit goes to Josh Triplett , who produced the 105-byte version which you can find…
The job of a software engineer is not to produce code, but to solve problems; we just happen to solve most of those problems by producing code. Ultimately, producing code is hard, and we need help. That's why GitHub's Copilot is exciting, but it's far from ideal, and it's the tip of the iceberg of what's been done and…
Backups are critical. If you are lucky and organised you have a set of useful backup primitives, such as Point in Time snapshots on your Infrastructure As A Service (IaaS), your disk array controller, or volume manager. However there always seems to be some critical machine in my life that does not fall into these…
Many folders have them. They’re so invisible that you can’t even see them when you show hidden files. And the only way you know they’re there is when they cause problems.
Understanding & mitigating randomly slow writes in PostgreSQL
If you're building an application that needs to scale—and we all tell ourselves that we are—then at some point you have to figure out if it does or not. This is where load testing comes in: if you want to see whether or not your application can handle scale, just generate scale and see if it can handle it! It sounds…
Thoughts on how to write automated tests for a TCP implementation.
As systems get big, people very reasonably start investing more in increasing efficiency and decreasing costs. That’s a good thing, for the business, for the environment, and often for the customer. Much of the time efficient systems have lower and more predictable latencies, and everybody enjoys lower and more…
I wrote this document after receiving large amounts of email from people who would like to write an emulator of one or another computer but do not know where to start. Any opinions and advices contained in the following text are mine alone and should not be taken for an absolute truth. The document mainly covers…
Earlier today, I saw a link on the ClassicCmp.org mailing list to a project to re-implement the DEC VAX CPU on an FPGA. Its entitled First new vax in ...30 years? Someone posted it on Hackernews . One of the comments said, roughly, that they didnt see the significance and…
It all started with the big bang! We nearly lost 33 of 36 disks on a Proxmox / Ceph Cluster; this is the story of how we recovered them.
Cache strategies that don't trade-off correctness for speed
Ray: A Distributed Framework for Emerging AI Applications Moritz, Nishihara, Wang et. al.
This post is part of a larger effort you can view over here: https://osblog.stephenmarz.com .
In this article we’ll learn how to build shared libraries and install them properly on several platforms. For guidance, we’ll examine the goals and history of dynamic linking on UNIX-based operating systems.
TL;DR: Some Linux distros and even different kernel versions within a distro have disabled IRQ time accounting. In such case, your monitoring tools will report zero time spent in hardware interrupt handlers (shown as %hi, %irq, hiq, etc). It’s easy to check how your kernel is behaving by looking at /proc/stat and you…
Updated: 2023-01-06 About a year ago I was bitten by the PL bug. It started with reading Crafting Interpreters and discovering the wonders hidden under the hood of a compiler. I am also been a big fan of Emacs, and this started to get me interested in how its interpreter works. At the same time, I was reading the Rust…
Earlier this year, I pitted the $549 ASUSTOR Lockerstor 4 NAS against a homebrew $350 Raspberry Pi CM4 NAS, and came to the (rather obvious) conclusion that the Lockerstor was better in almost every regard. Well, ASUSTOR introduced a new lower-cost NAS, the $329 Drivestor 4 Pro (model AS3304T—pictured above), and sent…
I have reached a good milestone on the SCAMP hardware: it can now execute code! It runs all the way through the test program correctly.
I’ve done a couple of posts on LLVM itself, mostly on things you can do with LLVM or how LLVM represents particular program features.
A list of things that we can do when we need to scale a SQL database.
