Date: Thu, 30 Apr 2009 08:46:41 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-acpi@freebsd.org Cc: acpi <acpi@freebsd.org>, freebsd-performance@freebsd.org, freebsd-hackers@freebsd.org, Pieter de Goeje <pieter@degoeje.nl> Subject: Re: ACPI-fast default timecounter, but HPET 83% faster Message-ID: <200904300846.41576.jhb@freebsd.org> In-Reply-To: <7d6fde3d0904261927s1a67cf85jc982c1a68e30e081@mail.gmail.com> References: <200904270150.31912.pieter@degoeje.nl> <7d6fde3d0904261927s1a67cf85jc982c1a68e30e081@mail.gmail.com>
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On Sunday 26 April 2009 10:27:42 pm Garrett Cooper wrote: > I'm seeing similar results. > > [root@orangebox /usr/home/gcooper]# dmesg | grep 'Timecounter "' > Timecounter "i8254" frequency 1193182 Hz quality 0 > Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 > Timecounter "HPET" frequency 14318180 Hz quality 900 > [root@orangebox /usr/home/gcooper]# ./cgt > 1369355 > [root@orangebox /usr/home/gcooper]# sysctl > kern.timecounter.hardware="ACPI-fast" > kern.timecounter.hardware: HPET -> ACPI-fast > [root@orangebox /usr/home/gcooper]# ./cgt > 772289 > > 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". -- John Baldwin
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