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Message-Id: <202110092107.199L7T4j059128@critter.freebsd.dk>
To: Warner Losh <imp@bsdimp.com>
cc: Konstantin Belousov <kostikbel@gmail.com>,
        Sebastian Huber <sebastian.huber@embedded-brains.de>,
        FreeBSD Hackers <freebsd-hackers@freebsd.org>
Subject: Re: Why was the timehands_count sysctl added?
In-reply-to: <CANCZdfr7_jb07+Aft_uo2F8L9hDr9iABaDkANioJhi-kQXQeoQ@mail.gmail.com>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
References: <2d1d2a6d-ec6b-7f52-8af3-09a833c52820@embedded-brains.de> <YWHzoTpcZTQcHVUw@kib.kiev.ua> <CANCZdfr7_jb07+Aft_uo2F8L9hDr9iABaDkANioJhi-kQXQeoQ@mail.gmail.com>
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Date: Sat, 09 Oct 2021 21:07:29 +0000
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--------
Warner Losh writes:

> > To allow for experimentation, and to satisfy some requests where people
> > wanted to have more that 2 timehands.
>
> When would someone want that? What's the use case?

The reason there were originally 10 timehands was that latency in
the early SMP kernels was ... ehh ... variable ... and some of the
time-counters rolled over quite fast compared to that.

I really hope no relevant current hardware has that problem.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.