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Re: Debian on Pine64 H64B?

On September 21, 2021 12:06:35 AM UTC, Paul Wise <pabs@debian.org> wrote:

>It sounds like you are talking about userland and Debian still supports
>a 32-bit userland under a 64-bit Linux kernel on 64-bit devices,

which... and i apologise, i cannot remember your name, our person-running-CNC-lathes pointed out that the latency on context-switches, presumably because of conversions on system calls between 64 and 32 bit and back, is awful, and making microsecond response time barely achievable.

microsecond response... 1e6.... clock speeds 2e9... bordering on 2,000 instructions for a contextswitch and syscall, any typeconversion is apparently too much.

> do
>these concerns also apply to the Linux kernel itself?

to a lesser extent given the relative size of the linux kernel, we may surmise only the most extreme resource constrained scenarios would be concerned about that, and they're likely to be using yocto, buildroot, Zephyr or other RTOS etc. custom from-source builds.

i had forgotten about the latency issue though, and was fascinated to hear that running CNCs is so borderline.

i wonder if x86 does so much better there due to hyperthreading.


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