[haiku-bugs] [Haiku] #9277: Date/Time Skew Depending on CPU Frequency Stepping Policy
- From: "br3wski3" <trac@xxxxxxxxxxxx>
- Date: Sun, 09 Dec 2012 23:35:49 -0000
#9277: Date/Time Skew Depending on CPU Frequency Stepping Policy
-------------------------------------------------+-------------------------
Reporter: br3wski3 | Owner: nobody
Type: bug | Status: new
Priority: normal | Milestone: R1
Component: - General | Version:
Keywords: cpu frequency date time skew | R1/alpha4.1
CPUFrequency | Blocked By:
Blocking: | Has a Patch: 0
Platform: All |
-------------------------------------------------+-------------------------
Hi,
I noticed that the date clock time has been falling behind with respect to
the real time. I have tracked this down to a dependence on the CPU
frequency. When I have the stepping policy with CPUFrequency set to
Dynamic performance or Low energy or explicitly set the state to a lower
than maximum frequency, the system clock time falls behind. When I have
the policy set to High performance or the max frequency, the system time
seems to keep up.
Here is an example of setting the time and checking the time skew at
various points with the policy set to Low energy which demonstrates the
severe skew. The time is retrieved/parsed from time.gov in the first call
and then compared subsequently a handful of times. I should also note that
the CPU max frequency is 1.6 GHz while the Low energy state puts it at 600
MHz.
{{{
~> date -s `curl 'http://www.time.gov/timezone.cgi?Eastern/d/-5' | grep -v
'meta http-equi' | grep '..:..:..' | sed -e 's/.*<b>//' -e 's/<.*//'`
% Total % Received % Xferd Average Speed Time Time Time
Current
Dload Upload Total Spent Left
Speed
100 4869 0 4869 0 0 35003 0 --:--:-- --:--:-- --:--:--
40915
Sun Dec 9 17:00:05 GMT 2012
~> curl 'http://www.time.gov/timezone.cgi?Eastern/d/-5' | grep -v 'meta
http-equi' | grep '..:..:..' | sed -e 's/.*<b>//' -e 's/<.*//'; date
% Total % Received % Xferd Average Speed Time Time Time
Current
Dload Upload Total Spent Left
Speed
100 4869 0 4869 0 0 11902 0 --:--:-- --:--:-- --:--:--
12613
17:00:07
Sun Dec 9 17:00:06 GMT 2012
~> curl 'http://www.time.gov/timezone.cgi?Eastern/d/-5' | grep -v 'meta
http-equi' | grep '..:..:..' | sed -e 's/.*<b>//' -e 's/<.*//'; date
% Total % Received % Xferd Average Speed Time Time Time
Current
Dload Upload Total Spent Left
Speed
100 4869 0 4869 0 0 16115 0 --:--:-- --:--:-- --:--:--
18100
17:00:27
Sun Dec 9 17:00:13 GMT 2012
~> curl 'http://www.time.gov/timezone.cgi?Eastern/d/-5' | grep -v 'meta
http-equi' | grep '..:..:..' | sed -e 's/.*<b>//' -e 's/<.*//'; date
% Total % Received % Xferd Average Speed Time Time Time
Current
Dload Upload Total Spent Left
Speed
100 4869 0 4869 0 0 31541 0 --:--:-- --:--:-- --:--:--
47735
17:41:59
Sun Dec 9 17:22:49 GMT 2012
~> curl 'http://www.time.gov/timezone.cgi?Eastern/d/-5' | grep -v 'meta
http-equi' | grep '..:..:..' | sed -e 's/.*<b>//' -e 's/<.*//'; date
% Total % Received % Xferd Average Speed Time Time Time
Current
Dload Upload Total Spent Left
Speed
100 4869 0 4869 0 0 52009 0 --:--:-- --:--:-- --:--:--
64920
17:55:03
Sun Dec 9 17:27:54 GMT 2012
}}}
As can be seen, the deviation increases steadily over the course of about
fifty-five minutes.
Now, a similar example sequence but with the Stepping policy in
CPUFrequency set to High performance.
{{{
~> date -s `curl 'http://www.time.gov/timezone.cgi?Eastern/d/-5' | grep -v
'meta http-equi' | grep '..:..:..' | sed -e 's/.*<b>//' -e 's/<.*//'`
% Total % Received % Xferd Average Speed Time Time Time
Current
Dload Upload Total Spent Left
Speed
100 4869 0 4869 0 0 18269 0 --:--:-- --:--:-- --:--:--
30242
Sun Dec 9 18:05:26 GMT 2012
~> curl 'http://www.time.gov/timezone.cgi?Eastern/d/-5' | grep -v 'meta
http-equi' | grep '..:..:..' | sed -e 's/.*<b>//' -e 's/<.*//'; date;
% Total % Received % Xferd Average Speed Time Time Time
Current
Dload Upload Total Spent Left
Speed
100 4869 0 4869 0 0 29417 0 --:--:-- --:--:-- --:--:--
34531
18:05:33
Sun Dec 9 18:05:32 GMT 2012
~> curl 'http://www.time.gov/timezone.cgi?Eastern/d/-5' | grep -v 'meta
http-equi' | grep '..:..:..' | sed -e 's/.*<b>//' -e 's/<.*//'; date;
% Total % Received % Xferd Average Speed Time Time Time
Current
Dload Upload Total Spent Left
Speed
100 4869 0 4869 0 0 19713 0 --:--:-- --:--:-- --:--:--
32245
18:26:30
Sun Dec 9 18:26:29 GMT 2012
}}}
As can be seen, over the course of more than twenty minutes, the
system/clock time remains in-line with time.gov.
I could not find any other ticket reporting this. Also, I do not know if
there is something specific about my system causing this but I'd be happy
to dig up any additional information that may be needed. The laptop
running Haiku R1 Alpha 4.1 from HD is a Dell Inspiron 600m.
Thanks!
Brendan
--
Ticket URL: <http://dev.haiku-os.org/ticket/9277>
Haiku <http://dev.haiku-os.org>
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