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Lalit Maganti

@lalitm.com

Founding engineer @ perfetto.dev Writing @ lalitm.com Building devtools like syntaqlite, buildprof in my spare time Senior Staff SWE @ Google

Posts Replies Media

Lalit Maganti @lalitm.com · 14/09/2026

syntaqlite, the very fast SQLite formatter just got another 19% faster. Someone reported a functional bug but fixing it made me realise if I restructured the AST slightly, a pile of simplifications fell out for free.

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Lalit Maganti @lalitm.com · 12/09/2026

I made a tool that shows where the time goes when you compile software. It’s called buildprof. Run it in front of any build command and it puts every process the build spawns on a timeline. It doesn’t care whether the build is Cargo, Ninja, Make, Zig or a pile of shell scripts.

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Lalit Maganti @lalitm.com · 11/09/2026

Got very interested in the performance of parsing of large Perfetto traces as I do once every few months. Managed to shave ~30% of the parse time of traces containing lots of typed arguments, common in traces from Chrome and AI workloads.

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Lalit Maganti @lalitm.com · 25/08/2026

Correlating profiles across different machines usually involves a lot of painful window-switching. Here’s a quick demo of doing it in Perfetto instead: two separate profiles, aligned on one timeline in a few clicks.

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Lalit Maganti @lalitm.com · 24/08/2026

Got a really fantastic comment on HN which I think perfectly captures the essence of my thinking.

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Lalit Maganti @lalitm.com · 23/08/2026

The staff engineering post I wrote a couple of weeks ago is currently #1 on Hacker News, which is a nice surprise. If you missed it: lalitm.com/post/find-pr...

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Lalit Maganti @lalitm.com · 19/08/2026

1/5 I've been on Opus 5 for a week and noticed the code comments stopped using em-dashes. It's all double hypens (--) now. Decided to do some analysis to confirm I wasn't fooling myself...

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Lalit Maganti @lalitm.com · 17/08/2026

PyTorch profiles are going to look much better in the upcoming release of Perfetto. Their events lack enough hierarchy, so Perfetto has to guess the layout. We now pack the tallest slice stacks first, making the same trace far more compact. Full explainer at lalitm.com/post/pytorch...

Perfetto timeline showing three repeated PyTorch call trees at progressively different vertical offsets. Broad ProfilerStep events push each later tree farther down the track.

The same PyTorch timeline after tallest-first packing. The three call trees align at the top, while all three ProfilerStep events share one row along the bottom, making the track much shorter.

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Lalit Maganti @lalitm.com · 17/08/2026

A day-to-day game-changer of LLMs is the ability to design really exhaustive benchmarks. This is the sort of thing I would have just been too impatient to do before. For example, I've spent around 30 minutes iterating and I've ended up with this...

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Lalit Maganti @lalitm.com · 05/08/2026

The duality of r/math

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Lalit Maganti @lalitm.com · 23/11/2025

The results? 189 bugs fixed. A 2021 feature request finally implemented (took just 1 day!). Team morale through the roof. And users actually notice the polish.

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