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Comment by hcrisp | Hacker News Reader

Reminds me of the story of the computer engineer at Data General in Traccy Kidder's nonficion book, "The Soul of a New Machine" [0], who quit after spending weeks toiling away on sub-second timing concerns:

> He went away from the basement and left this note on his terminal: "I'm going to a commune in Vermont and will deal with no unit of time shorter than a season."

[0] https://en.m.wikipedia.org/wiki/The_Soul_of_a_New_Machine

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What should I say, trying to go sub millisecond, one profiling run at a time, sigh...

Sub millisecond timing is basically impossible with context switching involved. Even on a real time kernel config, the best you are going to get with a time slice is 1ms.

With busy waiting, you can achieve timings in the sub-microsecond range, depending on how heavy the loop is.

Not sure what you mean by that but nanosecond precise timing across cpu cores have been reliable for quite a while now.

Key words: constant TSC, invariant TSC, TSC clocksource

The hardware providing those nanoseconds is not nanosecond accurate (unless using atomic clock)

However they may be more accurate than 1ms. The guy is saying the timeslice given by the OS for a program to run in has at best a 1ms slot because the OS is switching between threads on a 1ms timeslice basis

So unless you're polling, the timing at which you ask the hardware for nanoseconds will jitter with 1ms offsets

There are a lot of applications in the world that don't run on a regular processor under regular linux

The guy is overgeneralizing IMO. You can delve deep within the sub millisecond world even as a regular dude with a regular computer and a regular OS by just doing everything in an interrupt context

No, TSC on modern CPUs is much more granular that that. No atomic clocks needed, just a normal quartz crystal. This is how ptp works and you can definitely get sub nanosecond accuracy from it. Wrt scheduling quantum, this is entirely configurable and subject to scheduling policy, priorities and additional mechanics such as isolcpus and nohz. GP's comment is just plain wrong.

Maybe he should get Stephen Colbert's second-by-second day planner.

woah, do you have a link on that? I use plan [1] which is great for minute level planning but also annoying in various ways, if there's other software that can do similar, would love to try it

(i'm guessing that this was purely a joke and no such thing exists)

[1] https://help.supermemo.org/wiki/Plan

It was from a skit on the Colbert Report (can't remember the episode). He talks about how NASA added a leap second and then pulled out this comical "second-by-second" year planner and said his plans are ruined because he doesn't know what to do with the extra second. Wish I could remember it.

I definitely would like to find this episode. Not coming up on Google. Do you have any idea when it was broadcast? Thank you so much!

It's dumb you got downvoted for telling a joke, geez

Telling jokes on HN is risky. HN readers don't want the site full of jokes, so they savagely downvote them unless almost everyone finds them hilarious.

> geez

This is a euphemism. Please don't use it.

Why not, out of curiosity?

It's a euphemism for J-sus.

“In this is love, not that we loved God but that he loved us and sent his Son to be the expiation for our sins.” (1 Jn. 4:10)

Dissent, because for those of us who have never heard of such a connection (myself included) it is /not/ a euphamism but rather a safe epithet that the use of which never got anyone accused of "foul langauge" nor got anyone threatened with "mouth washed out with soap".

. o O ( The minor peril of disabling my autocorrect is that while my words may be inteligible, and both non sequiturs and wholly altered meanings may be avoided…spellings may occasionally falter. )

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