Date: Thu, 30 Apr 2009 22:52:45 +0100 From: Bruce Cran <bruce@cran.org.uk> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-hackers@freebsd.org, Pieter, freebsd-acpi@freebsd.org, Goeje <pieter@degoeje.nl>, freebsd-performance@freebsd.org Subject: Re: ACPI-fast default timecounter, but HPET 83% faster Message-ID: <20090430225245.538d073e@gluon.draftnet> In-Reply-To: <200904300846.41576.jhb@freebsd.org> References: <200904270150.31912.pieter@degoeje.nl> <7d6fde3d0904261927s1a67cf85jc982c1a68e30e081@mail.gmail.com> <200904300846.41576.jhb@freebsd.org>
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On Thu, 30 Apr 2009 08:46:41 -0400 John Baldwin <jhb@freebsd.org> wrote: > On Sunday 26 April 2009 10:27:42 pm Garrett Cooper wrote: > > Why's the default ACPI-fast? For power-saving functionality or > > because of the `quality' factor? What is the criteria that > > determines the `quality' of a clock as what's being reported above > > (I know what determines the quality of a clock visually from a > > oscilloscope =])? > > I suspect that the quality of the HPET driver is lower simply because > no one had measured it previously and HPET is newer and less "proven". > http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/dev/acpica/acpi_hpet.c shows some of the history behind the decision. Apparently it used to be slower but it was hoped it would get faster as systems supported it better. I guess that's happening now. -- Bruce Cran
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