Date: Sat, 9 Oct 2021 14:54:30 -0600 From: Warner Losh <imp@bsdimp.com> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Sebastian Huber <sebastian.huber@embedded-brains.de>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Why was the timehands_count sysctl added? Message-ID: <CANCZdfr7_jb07%2BAft_uo2F8L9hDr9iABaDkANioJhi-kQXQeoQ@mail.gmail.com> In-Reply-To: <YWHzoTpcZTQcHVUw@kib.kiev.ua> References: <2d1d2a6d-ec6b-7f52-8af3-09a833c52820@embedded-brains.de> <YWHzoTpcZTQcHVUw@kib.kiev.ua>
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--0000000000007ee9d405cdf1b484 Content-Type: text/plain; charset="UTF-8" On Sat, Oct 9, 2021, 1:56 PM Konstantin Belousov <kostikbel@gmail.com> wrote: > On Sat, Oct 09, 2021 at 09:41:28PM +0200, Sebastian Huber wrote: > > Hello, > > > > I synchronize currently the port of the FreeBSD timecounters to RTEMS and > > came across a change in 2019 which I do not understand. Some time ago the > > timehands were reduced from 10 to two: > > > > https://reviews.freebsd.org/D7302 > > > > In 2019 this changed again to be up to 16: > > > > https://reviews.freebsd.org/D21563 > This review did not changed it back to 16, the default value is still 2. > It allows to bump the number of used timehands, but normally systems run > with only 2. > > > > > The corresponding sysctl is not documented: > > > > https://www.freebsd.org/cgi/man.cgi?query=timecounters&sektion=4 > > > > Does someone know why this sysctl to select the count of timehands was > > added? Is this a performance optimization for some systems? > > 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? Warner > --0000000000007ee9d405cdf1b484--
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