Top all-time · #2731
Johnny's Software Lab
Company blog · johnnysswlab.comprogrammingsystems
Johnny's Software Lab is the company blog at johnnysswlab.com, writing about programming and systems. Since 2022, 28 different Hacker News readers have linked it 70 times, most often “Branches influence the performance of your code and what can you do about it”. It is still writing: the last post was on 2026-02-26, and you can follow it by feed.
Too few sampled comments (4) to say how often HN recommends it.?
Why HN links it
HN readers link Johnny's Software Lab for software performance posts on C/C++ topics such as CPU caches, memory access patterns and AVX/Neon vectorization. Comment discussion is sparse.
Summarised by Claude from a sample of 4 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Welcome to Johnny’s Software Lab, a blog for all interested in fast software written in C and C++. Your program doesn’t run fast enough? You need someone to talk to about your software’s performance? You or your team want to learn to write faster software? Whatever it is, we can help you. Check out
Most-linked posts?
- Branches influence the performance of your code and what can you do about it5 people · 5 mentions · first linked 2022-11-04
- Things Every Fresh Graduate Should Know About Software Performance4 people · 5 mentions · first linked 2025-09-20
- Faster hash maps, binary trees etc. through data layout modification3 people · 4 mentions · first linked 2023-09-30
- Floating-point error handling in C++: what works?3 people · 3 mentions · first linked 2026-02-18
- Memory Subsystem Optimizations (Article Series)3 people · 3 mentions · first linked 2024-11-13
- Horrible Code, Clean Performance3 people · 3 mentions · first linked 2023-04-14
- Measuring Memory Subsystem Performance2 people · 4 mentions · first linked 2023-08-01
- A story of a large loop with a long instruction dependency chain2 people · 3 mentions · first linked 2024-02-29
- Deep Dive in Java vs. C++ Performance2 people · 3 mentions · first linked 2025-12-06
- For Software Performance, the Way Data Is Accessed Matters2 people · 2 mentions · first linked 2022-11-12
What Hacker News says?
This whole article seems to be picking a lot of nits. I didn't read it too deeply, so feel free to correct me if I'm wrong, but the biggest complaints highlighted in the article are: 1. Modern CPUs use instruction level parallelism (ILP) 2. Memory isn't linear (you have separate caches, L1, L2, L3 and main memory) If you've ever debugged a C or C++ program in release, you've quickly found out about ILP. The code sti…
Comment linking /instruction-level-parallelism-in-practice-speeding-up-memory-bound-programs-with-low-ilp/
on “Build Your Own Redis with C/C++”Submitted The messy reality of SIMD (vector) functions as a story · 120 points
HN discussionCaches and Memory Systems have to be looked at from three related perspectives viz. a) Hardware/SoC/Physical level b) OS/Compiler system software level c) Applications usage level. To that end; 1) Buy/Beg/Borrow/Steal the Curt Schimmel book mentioned above. That one book will teach you all about how OSes manage caches/memory for SMP multiprocessing systems. You really get to understand multiprocessing at a fundament…
Comment linking /make-your-programs-run-faster-by-better-using-the-data-cache/
on “A concrete explanation of how a cache works”Submitted Unexpected ways memory subsystem interacts with branch prediction as a story · 89 points
HN discussionPart 2 is also now available https://johnnysswlab.com/decreasing-the-number-of-memory-acc...
Comment linking /decreasing-the-number-of-memory-accesses-the-compilers-secret-life-2-2/
on “Decreasing the Number of Memory Accesses 1/2”Submitted Growing Buffers to Avoid Copying Data as a story · 42 points
HN discussionHi! I am Ivica, I am the guy working for Johnny's Software Lab (johnnysswlab.com) - web site and one man company that specializes in software performance. A few times I saw posts from my web site here, that means at least some people find this topic interesting. I know people don't like sales pitches, but this is exactly what it is, admins please forgive me. For all software developers who want to speed up their sof…
Comment linking /avx-neon-vectorization-workshop/
on “AVX/Neon Vectorization Workshop”Submitted Link Time Optimizations: New Way to Do Compiler Optimizations as a story · 39 points
HN discussionSubmitted A story of a large loop with a long instruction dependency chain as a story · 39 points
HN discussionSubmitted Avoiding register spills in vectorized code with many constants as a story · 38 points
HN discussionSubmitted An optimizing compiler doesn't help much with long instruction dependencies as a story · 35 points
HN discussionSubmitted Performance Debugging with LLVM-mca: Simulating the CPU as a story · 33 points
HN discussionSubmitted The messy reality of SIMD (vector) functions as a story · 30 points
HN discussionSubmitted Loop Optimizations: taking matters into your hands (2021) as a story · 20 points
HN discussionSubmitted CPU Dispatching: Make your code both portable and fast (2020) as a story · 11 points
HN discussionSubmitted Deep Dive in Java vs. C++ Performance as a story · 4 points
HN discussionSubmitted The price of dynamic memory: Memory Access (2020) as a story · 3 points
HN discussionSubmitted Things Every Fresh Graduate Should Know About Software Performance as a story · 3 points
HN discussionSubmitted Things Every Fresh Graduate Should Know About Software Performance as a story · 3 points
HN discussionSubmitted Excessive copying in C++ and your program's speed as a story · 3 points
HN discussionSubmitted Exposing More Parallelism Is the Reason Why Some Vectorized Loops Are Faster as a story · 2 points
HN discussionSubmitted Deep Dive in Java vs. C++ Performance as a story · 2 points
HN discussionSubmitted Branches influence the performance of your code and what can you do about it as a story · 2 points
HN discussionSubmitted Memory Subsystem Optimizations (Article Series) as a story · 2 points
HN discussionSubmitted 9 Things Every Fresh Graduate Should Know About Software Performance as a story · 2 points
HN discussionSubmitted Performance Debugging with LLVM-mca: Simulating the CPU as a story · 2 points
HN discussionSubmitted Memory Subsystem Optimizations – The Remaining Topics – Johnny's Software Lab as a story · 2 points
HN discussionSubmitted Faster hash maps, binary trees etc. through data layout modification as a story · 2 points
HN discussionSubmitted Performance Through Memory Layout as a story · 2 points
HN discussionSubmitted Software Performance and Class Layout as a story · 2 points
HN discussion
