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@eniko says "i won't infodump without permission, but here's the short version", writes two hundred words anyway. the struggle to contain oneself can sometimes really be immense, huh 🫠

@eniko I am swamped with work right now, otherwise I would ask for permission to infodump :D

TLDR is there's thousands (or at least multiple hundred) counters inside the CPU that tick up for all kinds of performance- and otherwise relevant events (cache misses for example) and each OS gives you a way to read these out, plus the kernel can make sure it's properly accounted per process or thread and whatnot. some of these counters are preposterously specific, like uhhhhhh "Number of cycles dispatch is stalled for integer scheduler queue 3 tokens". But there's usually a little selection of commonly useful ones available with some extra simple command.

It's absolutely fascinating what you can, in theory, do if you want to dig really really really far down, but to be honest, I usually get very little really actionable insights from anything more intricate than the most basic ones ;(

absolutely a skill issue from my end I'm convinced!

@eniko do you already have experience with the kind of profiler that lets you get performance counter values?

on linux my go-to first step is perf stat -d ./myprogram (-d for details gives a couple more numbers. gotta have numbers!) then you'll see a few numbers that may point at a drastic difference.

I'm thinking a higher instruction per cycle number probably means fewer instructions that take many cycles (though I hear integer division is much better nowadays?), or your cache hit rate for data or instruction cache may be a lot better, or maybe your code ends up with fewer total instructions for some reason?

@mcc the third ratchet is ratcheted by the government official that takes care of you and whoever you're talking to, of course

@mcc pff, this is obviously just engagement bait

@NocturneGames https://arxiv.org/abs/2504.17033 here's the paper for the algorithm, i didn't spot a link to it in the article