Date: Tue, 30 May 2006 19:05:39 -0400 (EDT) From: "Andrew R. Reiter" <arr@watson.org> To: Jeremie Le Hen <jeremie@le-hen.org> Cc: freebsd-current@freebsd.org Subject: Re: [fbsd] timer goes sluggish Message-ID: <20060530190500.V48676@fledge.watson.org> In-Reply-To: <20060530223226.GT1890@obiwan.tataz.chchile.org> References: <20060529153103.GA17178@obiwan.tataz.chchile.org> <20060530223226.GT1890@obiwan.tataz.chchile.org>
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On Wed, 31 May 2006, 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'' :). : :> % jarjarbinks:root# ntpdate -b chronos.cru.fr :> % 29 May 17:09:32 ntpdate[4266]: step time server 195.220.94.163 offset 0.000937 sec :> % jarjarbinks:root# sysctl kern.timecounter.hardware=TSC :> % kern.timecounter.hardware: ACPI-fast -> TSC :> % jarjarbinks:root# while : ; do date ; sleep 1 ; done :> % Mon May 29 17:09:41 CEST 2006 :> % Mon May 29 17:09:42 CEST 2006 :> % Mon May 29 17:09:43 CEST 2006 :> % Mon May 29 17:09:44 CEST 2006 :> % Mon May 29 17:09:45 CEST 2006 :> % ^C :> % jarjarbinks:root# ntpdate -b chronos.cru.fr :> % 29 May 17:10:16 ntpdate[4278]: step time server 195.220.94.163 offset 29.503343 sec : :Likewise, we the above sysctl set, this behaviour disappears. However, :I think humbly that this breaks POLA. I am pretty confident there is :a good technical reason for this, but it is quite puzzling to have :the computer clock drifting lagging that much. : : :As an additional question, is there a reason to have :performance_cx_lowest="LOW" in etc/defaults/rc.conf ? : I think the problem lays within the name of the host. J/K.! Cheers, Andrew -- arr@watson.org
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