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jerrinot
Joined 271 karma
- jerrinotI have no practical experience with bpftrace, so it did not occur to me. I'll give it a try and perhaps there's gonna be a 2nd part of this investigation.
- It's much tougher when it's so hard to reproduce. Perhaps the NMI watchdog could help? https://docs.kernel.org/admin-guide/lockup-watchdogs.html
- Wow, someone is actually reading the article in detail, that's a good feeling! In C, the != operator has higher precedence than the || operator. That said, extra parentheses never hurt readability.
- Thanks for the kind words!
Heatmaps are amazing for pattern spotting. I also use them when hunting irregular hiccups or outliers. More people should know about this feature.
- Author here. I've always been kernel-curious despite never having worked on one myself. Consider this either a collection of impractical party tricks or a hands-on way to get a feel for kernel internals.
- Snowflake did not acquire RP after all.
- I expect candidates to suggest similar optimisations, but I felt it was unnecessary for the article itself.
- That’s a neat trick, albeit with limited applicability given the very narrow range. Thanks for sharing!
- That's a very good question. A proper compiler engineer would know, but I will do my best to find something and report back.
Edit: I could not find any pass with a pattern matching to replace CAS loops. The closest thing I could find is this pass: https://github.com/llvm/llvm-project/blob/06fb26c3a4ede66755... I reckon one could write a similar pass to recognize CAS idioms, but its usefulness would be probably rather limited and not worth the effort/risks.
- Hi, author here. My superpower is spending unreasonable amounts of time researching things with no practical purpose. Occasionally I blog about it - as a warning to others.
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- A QuestDB engineer here: These are cool benchmarks! The idea to try Robin Hood probing came to me after receiving some feedback on Reddit. I ran initial experiments, and the results were promising, leading to its integration into our codebase. Thank you so much for sharing your repository. Perhaps one day we'll explore bidirectional probing as well!
A snapshot of my happiness after running first experiments with Robin Hood: https://twitter.com/jerrinot/status/1730147245285150743 :)
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- What are your requirements? We see some people switching from InfluxDB to QuestDB. Common reasons include SQL support (InfluxDB strategy is a bit confusing here), performance and issues with high-cardinality in InfluxDB.
Full Disclosure: I work for QuestDB and I am obviously biased.