Just as this question was raised on SLUG someone on linux-il had the same
problem. Disabling SMP solved it.
--Amos
---------- Forwarded message ----------
From: shimi <[EMAIL PROTECTED]>
Date: 23-Apr-2007 08:03
Subject: Time Drifting Back & Forth on SMP [Was: Re: System Clock is crazy?
[was: Re: vixie-cron acting weird (actually not acting at all)]]
To: linux-il <[EMAIL PROTECTED]>
Replying again to myself :-)
On Sunday 22 April 2007 00:58, shimi wrote:
Replying to myself because I found the CAUSE, but not the REASON.
toast ~ # date
Sun Apr 22 01:25:13 IDT 2007
toast ~ # date
Sun Apr 22 00:52:25 IDT 2007
toast ~ # date
Sun Apr 22 01:25:14 IDT 2007
toast ~ # date
Sun Apr 22 00:52:26 IDT 2007
toast ~ # date
Sun Apr 22 01:25:15 IDT 2007
toast ~ # date
Sun Apr 22 00:52:27 IDT 2007
toast ~ # date
Sun Apr 22 01:25:17 IDT 2007
toast ~ # date
Sun Apr 22 00:52:29 IDT 2007
toast ~ # date
Sun Apr 22 01:25:18 IDT 2007
toast ~ # date
Sun Apr 22 00:52:32 IDT 2007
toast ~ # date
Sun Apr 22 01:25:21 IDT 2007
Appears time is alternating 32 minutes back and forth all the time
(perhaps
every second or so?). The kernel internal timekeeping seems to work. If I
issue a "sleep 5" at the shell, it returns after 5 seconds. However if I
TIME that command I am receiving very weird results, like:
# time sleep 5
real -.m+*.253s
user 0m0.000s
sys 0m0.000s
# time sleep 5
real 33m7.761s
user 0m0.000s
sys 0m0.000s
Obviously 'time' is looking at the same alternating value that 'date' is.
Same goes for 'ps' - I look at the process start time, and every time I
invoke 'ps', all the values go 32 minutes back and forth in time.
I stopped ntpd and it is still happening so this is not the cause.
Still looking for ideas :)
With the help of a friend's Google searching abilities, my first idea of
multiprocessors become even more probable for the reason for this behavior.
I
tried recompiling the kernel, changing some RTC related options - to no
avail.
Also, I have noticed, that when booting, the drift is "small" - like - 20
seconds or so. As time passes, it gets bigger and bigger.
Then, I tried booting the machine with the kernel option maxcpus=1. Problem
Gone.
OK, so now I got one CPU less and a greatly working system. I could stay
here,
but I'ld be happy to utilize the other core as well, so I am _still_ looking
for hints (especially from the kernel/SMP experts :-))
Thanks,
-- Shimi
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