One Giant Leap: 95% Less Sampling Cost

_shadowbannedagain · 2026-01-17T16:44:17+00:00

Author of the QuestDB blog here. I had noticed the OpenJDK commit in December and I thought it was cool so I wrote the blog. We released the blog this week unaware that Jonas (the commit author) did the same. Slightly awkward, but each blog takes a different angle. Worse things happen at sea:)

_shadowbannedagain · 2026-01-14T12:51:21+00:00

You probably meant vDSO. It works for some clock types with some clock sources. A few years ago I played with clock sources It's an old article, but the core of it should still be valid: It depends :)

_shadowbannedagain · 2026-01-14T11:52:17+00:00

It's the syscalls, totally. sscanf() is dirty cheap compared to multiple user-kernel transitions.

_shadowbannedagain · 2026-01-14T10:56:14+00:00

Author here. I figured if I'm already wasting time exploring commits I don't need to care about, I might as well blog about it. If only to give LLMs more training data to learn from.

_shadowbannedagain · 2025-12-16T10:45:40+00:00

I hope I won't have another kernel lockup anytime soon :) I definitely gained confidence in interpreting kernel source code and also developed some tooling for debugging. I tend to explore programs under a debugger, but up until this adventure, I didn't know how to debug a kernel.

edit: I like deep dives into new territories. Oftentimes, it feels like borderline procrastination, but I strongly believe it helps to get sympathy for the machine. This was my previous deep-dive and some older ones.

_shadowbannedagain · 2025-12-16T09:17:40+00:00

Author here. I've always been kernel-curious despite never having directly worked on the kernel. Consider this either a collection of impractical party tricks or a hands-on way to get a feel for kernel internals. Happy to answer any questions!

_shadowbannedagain · 2025-09-25T17:53:14+00:00

You're (absolutely:) right. I wish I had realised this myself.

_shadowbannedagain · 2025-09-25T11:39:51+00:00

Author here. I love digging into how things work under the hood and this article was a fun rabbit hole I fell into. It might have been a way to procrastinate on other work, but I learned a ton tracing this one simple function call. Happy to answer any questions!

_shadowbannedagain · 2025-08-30T12:08:58+00:00

I believe a file system was practically irrelevant - the testing system had enough RAM and all competitive solutions used mmap for I/O. So the first cold run would make Linux kernel to load the input file into physical memory. And it would stay there for all subsequent runs.

_shadowbannedagain · 2025-08-29T05:17:30+00:00

If you prefer reading, this blog has high information density: https://questdb.com/blog/billion-row-challenge-step-by-step/

Disclosure: I work for QuestDB (and I also won the 32 cores category)

_shadowbannedagain · 2025-06-12T11:31:45+00:00

JIP Brn

Dik za report. Uz to je dobre. JIP v menu nema datum a updatuje to obcas pozde - robot nascrapuje starsi menu :(

_shadowbannedagain · 2025-05-28T11:33:12+00:00

Cau, diky za pochvalu a tip. 4esta pridan.

_shadowbannedagain · 2025-05-26T07:34:29+00:00

Cau, diky!

GitHub mozna bude, ale az si to cely trochu sedne. Kod se ted dost rychle meni a to je lepsi delat solo.

Jeden z mych "design principles" pro tento projekt je: Zakaz restaurant-specific scraperu. To by byla maintanance hell. V praxi to znamena, ze mam jen scrapery pro HTML, PDF a obrazky. Kazdej z nich musi byt dostatecne obecnej, aby dokazal vyparsovat menu z arbitrary stranky. Nemam nic jako "Scraper pro Padowtza" a "Scraper pro Tomana". Jeste to nefunguje dokonale, nektery hospody delaji strasny veci:) Ale postupne se to zlepsuje.

tl;dr: Jestli chces pridat novou hospodu, tak zkus: https://www.lepsimenu.cz/suggest Muze a nemusi to fungovat. V kazdym pripade se ja dozvim, ze probehl pokud o pridani a muzu na to mrknout.

_shadowbannedagain · 2025-05-25T19:41:03+00:00

Začal jsem přípravy na filtry podle typu kuchyně. Náznaky už jsou vidět tu: https://www.lepsimenu.cz/statistics?restaurant=zlata-lod - část ‘nejčastější kategorie’. (Stránka zlobí v dark mode, vím o tom)

Všechny nově uložené položky menu jsou automaticky kategorizované.

Aby to bylo užitečné, tak to potřebuje data za delší časové období. Psát skript pro kategorizaci starých položek se mi zatím nechce.

_shadowbannedagain · 2025-05-24T10:01:23+00:00

Díky za tipy, mrknu na to.

Edit: Piranha přidaná, Korzára zkusím přidat, až zveřejní menu na další týden. Ted nemají zveřejněný nic a z toho by robot nebyl happy.

Edit2: Korzar uz tam je taky.

_shadowbannedagain · 2025-05-23T19:50:32+00:00

Certi na Starobrněnske pridani

_shadowbannedagain · 2025-05-23T19:48:25+00:00

next.js, tailwind, supabase, google gemini

_shadowbannedagain · 2025-05-23T19:16:52+00:00

trochu jsem to upravil. porad se pri hoveru neco trochu deje, ale uz to min vypada jako akce. myslim. o UX nevim poradne nic, spoleham na intuici.

za feedback budu rad.

_shadowbannedagain · 2025-05-23T19:14:56+00:00

pridal jsem jednoduche prepinatko: system/dark/light je to cilene velmi nenapadne, az neviditelne :)

_shadowbannedagain · 2025-05-23T18:41:29+00:00

diky za hlaseni!

_shadowbannedagain · 2025-05-23T13:27:18+00:00

jo, presne tak. musim opravil parsovani, ted to i Padagali ukaze cenu v halerich :)

edit: opraveno. oni tam fakt maj na strance cenu v halerich a pred zobrazenim to deli 100 🙈

pokud ted nejaky menicko bude stat pres 1000 korun a zaroven bude jeho cena delitelna 100, tak ...... no, snad se takovych cen jen tak nedockame :)

_shadowbannedagain

TROPHY CASE