Date: Sat, 7 Sep 2019 18:58:13 -0700 From: Conrad Meyer <cem@freebsd.org> To: "Constantine A. Murenin" <cnst++@freebsd.org> Cc: "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org> Subject: Re: What value HZ? Message-ID: <CAG6CVpU8732Ci0QM7=tBn0ifHf8yO-53FBtvBCF34StBDTCx-A@mail.gmail.com> In-Reply-To: <CAPKkNb4ETFzD7pXi3=iDUxtSxZSffxFB5q9ZtmsJy2FUuaZB5A@mail.gmail.com> References: <201909060119.x861JWrG006910@repo.freebsd.org> <4917d7507b6ea6c360dccda261f53052aa085f2b.camel@freebsd.org> <5EE266EE-E650-48D8-9B0E-E674AD026470@freebsd.org> <3cb6429acc7e520932d2c906d1cac47540156355.camel@freebsd.org> <8F03EA29-0F3F-4321-9241-78F7C924FDE1@freebsd.org> <CANCZdfr6pz19NCLmsua6iGzusotrcHN=u47RH7Y1PdM4rnomZA@mail.gmail.com> <9BC03B61-F8B5-476C-AD34-9DEA5230BFCF@freebsd.org> <CANCZdfqbp%2BU3=0EM2n3bhg4DwXd_PVjvEYjGyQhkE5-MK-3-QA@mail.gmail.com> <CAPKkNb4ETFzD7pXi3=iDUxtSxZSffxFB5q9ZtmsJy2FUuaZB5A@mail.gmail.com>
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Hi Constantine, On Sat, Sep 7, 2019 at 3:05 PM Constantine A. Murenin <cnst++@freebsd.org> wrote: > > For the sake of discussion, I recall that there was a measurable power > consumption difference between FreeBSD (HZ=3D1000) and OpenBSD (HZ=3D100)= when > I played with a Kill-A-Watt a number of years ago. Unfortunately, this is an apples to oranges comparison, and perhaps worse, vague and dated. It would be more interesting to compare HZ=3D1000 to HZ=3D100 with an otherwise identical CURRENT FreeBSD system. As far as I can tell, FreeBSD grew "tickless" timer support in r212541 in 2010 (thanks mav@). This is easily observed on my idle HZ=3D1000 amd64 system with 'vmstat -i': "cpu0:timer" is firing at an average rate of 21 Hz =E2=80=94 not 1000. And that is the most frequent interrupt. > Would it perhaps be prudent to try to qualify whether, and by how much, > this change affects power consumption on MIPS/ARM/RISCV, not just whether > each arch could cope with the change? If someone has the time and inclination, then of course, it could be an interesting test to run. Best, Conrad
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