Date: Sun, 14 Jun 2009 13:39:37 +0100 From: Kris Kennaway <kris@FreeBSD.org> To: John Baldwin <jhb@freebsd.org> Cc: acpi <acpi@freebsd.org>, freebsd-hackers@freebsd.org, freebsd-acpi@freebsd.org, Pieter de Goeje <pieter@degoeje.nl>, freebsd-performance@freebsd.org Subject: Re: ACPI-fast default timecounter, but HPET 83% faster Message-ID: <4A34EF89.10107@FreeBSD.org> 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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John Baldwin wrote: > 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". > From memory, HPET was massively slower on some of the AMD test hardware I was using. There was a thread about it on one of the mailing lists, but I can't find it right now. Kris
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