Date: Mon, 7 Aug 2006 12:43:10 -0400 From: John Baldwin <jhb@freebsd.org> To: Jeremie Le Hen <jeremie@le-hen.org> Cc: freebsd-current@freebsd.org Subject: Re: [fbsd] Re: [fbsd] timer goes sluggish Message-ID: <200608071243.10476.jhb@freebsd.org> In-Reply-To: <20060805090119.GM4498@obiwan.tataz.chchile.org> References: <20060529153103.GA17178@obiwan.tataz.chchile.org> <200606011441.07494.jhb@freebsd.org> <20060805090119.GM4498@obiwan.tataz.chchile.org>
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On Saturday 05 August 2006 05:01, Jeremie Le Hen wrote: > Hi John, > > On Thu, Jun 01, 2006 at 02:41:07PM -0400, John Baldwin wrote: > > On Tuesday 30 May 2006 18:32, Jeremie Le Hen wrote: > > > Hi, > > > > > > On Mon, May 29, 2006 at 05:31:03PM +0200, Jeremie Le Hen wrote: > > > > Hi, > > > > > > > > I won't write too much, the following session will tell much more: > > > > > > > > % jarjarbinks:root# ntpdate -b chronos.cru.fr > > > > % 29 May 17:08:44 ntpdate[4254]: step time server 195.220.94.163 offset > > 0.000273 sec > > > > % jarjarbinks:root# sysctl kern.timecounter.hardware > > > > % kern.timecounter.hardware: ACPI-fast > > > > % jarjarbinks:root# while : ; do date ; sleep 1 ; done > > > > % Mon May 29 17:08:56 CEST 2006 > > > > % Mon May 29 17:09:03 CEST 2006 > > > > % Mon May 29 17:09:09 CEST 2006 > > > > % Mon May 29 17:09:16 CEST 2006 > > > > % Mon May 29 17:09:22 CEST 2006 > > > > % ^C > > > > > > Sometimes, I feel dumb. > > > > > > I noticed that the clock sped up when the CPU makes heavy computing, > > > which meant there was some power saving on idleness. > > > > > > I dug a bit I found that hw.acpi.cpu.cx_lowest=C4. > > > Setting it hw.acpi.cpu.cx_lowest=C1 makes the clock goes ``in time'' :). > > > > If you are using APIC, try disabling APIC and see if it works ok with higher > > Cx states. > > Sorry for the delay. > > I was indeed using APIC, and got a chance to disable it. I am writing > this mail with C4 state set and it works flawlessly: > > % # sysctl hw.acpi.cpu.cx_lowest > % hw.acpi.cpu.cx_lowest: C4 > % # while : ; do date ; sleep 1 ; done > % Sat Aug 5 10:54:19 UTC 2006 > % Sat Aug 5 10:54:20 UTC 2006 > % Sat Aug 5 10:54:21 UTC 2006 > % Sat Aug 5 10:54:22 UTC 2006 > > > What's the point in disabling apic ? Am I supposed to lose some > features along with the apic support removal, or is it something I > won't notice ? On a laptop you probably won't notice unless it is a dual-core CPU or one with HT (and you want to use the HT) as disabling APIC disables support for SMP on x86. -- John Baldwin
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