Alfonso Subiotto

I'm happy to share that I will be speaking at #QConLondon on March 16 on deterministic simulation testing at Polar Signals. For anyone interested in attending: SPEAKER60QUK26 for £60 off

Claude is down. I guess I have to learn how to code again.

Introducing the Sandwich View A new way to visualize a function’s callers and callees side by side.

📢 It’s a new year so we’re announcing something new which is the Sandwich view: A way to visualize a function’s callers and callees side by side for better debugging and performance work. Read more about it here: www.polarsignals.com/blog/posts/2...

My EuroRust talk has been uploaded to YT! I cover how we architected our Rust database at @polarsignals.com as a set of state machines to enable deterministic simulation testing and catch hard-to-reproduce bugs before they hit prod.

Absolutely! I can't imagine going back to not having continuous system-wide profiling 🙈

performance[vortex-array]: don't call is_valid to count bytes in varbinview by asubiotto · Pull Request #5814 · vortex-data/vortex I noticed that the better blocks compressor uses count_referenced_bytes which calls is_valid on each view and results in an expensive scalar_at call. This was 30% of our system-wide CPU usage over ...

A simple 50-line code change saves us 30% of CPU across our whole infrastructure. This is the magic of system-wide profiling with @polarsignals.com. Easy to spot, easy to fix.

Profiling NVIDIA CUDA in Kubernetes The easiest way to get started Profiling CUDA in Kubernetes

🚀 We recently announced our NVIDIA CUDA always-on profiler. Check out this blog on how to try it out super quickly with your CUDA workload today!🧊

www.polarsignals.com/blog/posts/2...

Happy to share that I've been nominated to the Vortex Technical Steering Committee! It's been fun and productive switching to Vortex from Parquet as our storage format @polarsignals.com and I'm excited to continue contributing to the Vortex project.

vortex.dev/blog/novembe...

Great Lakes: A Delta Lake Fork Our updates to Delta Lake Table Format

🧊 New on the Polar Signals Blog — Our Delta Lake Fork

Purpose-built for our continuous profiling product. In our latest post, we walk through how Delta Lake works, and the changes we've made to improve performance for our product.

👉 Read the full post: buff.ly/KwHINtO

Do more with less. | Polar Signals Polar Signals Cloud is an always-on, zero-instrumentation continuous profiling for CPU, GPU, and Memory that helps improve performance, understand incidents, and lower infrastructure costs.

www.polarsignals.com/blog/posts/2...

Do more with less. | Polar Signals Polar Signals Cloud is an always-on, zero-instrumentation continuous profiling for CPU, GPU, and Memory that helps improve performance, understand incidents, and lower infrastructure costs.

Sometimes an interface is so ubiquitous that performance limitations inherent to its design are just accepted. This has been our experience with Parquet. We switched to Vortex which aligned much better with our needs and saw a 70% performance improvement across the board. Read more below 👇

The Inner Workings of JavaScript Source Maps A deep dive into how JavaScript source maps work under the hood, with examples showing how all the pieces fit together.

Ever wondered how your browser devtools jumps from bundle.min.js:1:27698 → src/index.ts:73:16? 🧊

We unpack the internals of JS Source Maps: Base64 VLQ encoding, mapping deltas, and how your original TS code gets reconstructed from minified bundles.

🔗 www.polarsignals.com/blog/posts/2...

Introducing the world's first open source continuous NVIDIA CUDA profiler. Zero code changes required, low overhead, and always on.

Took advantage of the lunch break to replay this great talk by Alfonso Subiotto (@asubiotto.com) making the case for a State Machines based approach to Deterministic Simulation Testing, being used at @polarsignals.com, very interesting!

Their inspiration for this: sled.rs/simulation

We're excited to be at @rustconf.com 2025!
Let's talk about profiling Rust with zero compromise!
#rustconf25

Parallel Flame Graph Rendering How we improved our flame graph rendering by moving computation to the backend.

We recently made some performance improvements to our Flame Graph by implementing backend pre-computation and viewport culling. Read more in our latest blog post: www.polarsignals.com/blog/posts/2...

I wrote about why we should treat German string encoding/StringViews as Just Another Encoding™

Thanks for the pointer. Do you know where though? This is what I could find of the representation: github.com/vortex-data/.... Also the pushed-down filter kernel seems to convert to arrow and delegate: github.com/vortex-data/.... In arrow I'm pretty sure the prefixes are not a separate array.

Do any database systems "columnarize" the German string encoding so rather than storing a 16-byte view for each element which includes length+prefix+pointer you'd store all lengths together, prefixes together etc...? Seems like prefix operations would be more SIMD friendly.

The hardest part about writing a blog post is the introduction. Here I am, 4 hours later.

OOMProf - Profiling on the Brink Using eBPF to record your programs dying breathes

Tame the OOM killer with OOMProf, the new eBPF memory profiler for Go programs being taken out by the kernels OOM killer!
www.polarsignals.com/blog/posts/2...

Offline Mode for the Parca Agent Collect and upload profiles -- even without a network connection

We're excited to share that the Parca Agent now works offline! Store CPU profiles locally when disconnected, upload when ready. Because not all computing happens in data centers.
Read how we built it: www.polarsignals.com/blog/posts/2...

Problem: Everything is JSON. Solution: MORE JSON!

Haha, but thanks for pointing this out. Now I'm going to have to do a little researching

New storage format RFC in the works 👀 Early preview:

Introducing Off-CPU Profiling How Off-CPU profiling works and how to get the most out of it

🚀 Today, we're excited to launch Off-CPU profiling! Check out our blog on what we needed to do to make it most useful and how you can get started with it! 🧊

www.polarsignals.com/blog/posts/2...

Unfortunately no plans to be in SF around then but we'll keep it in mind in case anyone does end up being there.

@metalmatze.de built an MCP server so you can hook up your agent to your profiling data. Check it out!

Deterministic Simulation Testing in Rust: A Theater Of State Machines How we designed our database for complete control over concurrency, time, randomness, and failure injection.

📔Writing our Rust database from scratch gave us a golden opportunity to implement deterministic simulation testing as a core feature. Learn about the architecture that gives us full control over DST ingredients. 🧊

www.polarsignals.com/blog/posts/2...

I assumed links were downranked everywhere, good to know!

Deterministic Simulation Testing in Rust: A Theater Of State Machines How we designed our database for complete control over concurrency, time, randomness, and failure injection.

www.polarsignals.com/blog/posts/2...