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Wrong idle time in /proc/uptime, anyone ?
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aCOSwt
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PostPosted: Thu Jul 25, 2013 8:58 am    Post subject: Wrong idle time in /proc/uptime, anyone ? Reply with quote

I suspect the idle time in /proc/uptime to be wrong.
At first it is greater than 2*uptime (on a dual core system)
Code:
$ cat /proc/uptime
13743.06 [35517.30]

And second it is far from being USER_HZ times the second entry in the /proc/uptime pseudo-file. As man proc tells.
Code:
$ cat /proc/stat
cpu  129971 3649 17017 [2499837] 47800 3 208 0 0 0

(USER_HZ=1/100th of a second for my arch)
Anyone to confirm ? Under which kernel ? dynticks dis/en-abled ?
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ulenrich
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PostPosted: Thu Jul 25, 2013 5:40 pm    Post subject: Re: Wrong idle time in /proc/uptime, anyone ? Reply with quote

aCOSwt wrote:
(USER_HZ=1/100th of a second for my arch)
Anyone to confirm ? Under which kernel ? dynticks dis/en-abled ?

HZ=300, no dynticks.
Code:
uname -r; cat /proc/uptime
3.10.2-1103.bd3r
452.15 721.21
 maci etc # cat /proc/stat
cpu  4883 12 645 79804 11854 0 105 0 0 0
cpu0 2159 4 230 40582 5539 0 105 0 0 0
cpu1 2723 8 414 39221 6315 0 0 0 0 0
intr 523192 174812 0 0 0 0 0 0 0 1 3 0 0 0 0 0 0 0 27 3938 0 307 4794 435 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 24899 0 1904 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ctxt 386300
btime 1374773427
processes 1907
procs_running 1
procs_blocked 0
softirq 346282 0 294459 3 44 24673 0 3045 0 1 24057

I have just compiled linux-3.10.2+100-3rc1-patches with BFS enabled. I don't yet know what these numbers are. I have booted ca 2 minutes ago.
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aCOSwt
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PostPosted: Thu Jul 25, 2013 8:19 pm    Post subject: Re: Wrong idle time in /proc/uptime, anyone ? Reply with quote

ulenrich wrote:

Code:
uname -r; cat /proc/uptime
3.10.2-1103.bd3r
452.15 [721.21]
 maci etc # cat /proc/stat
cpu  4883 12 645 [79804] 11854 0 105 0 0 0


Thank you for helping ulenrich.
I put brackets around the figures I am interested in.
As a matter of fact, if, what I imagine, you waited less than 70/2=35 seconds after cat /proc/uptime before issuing cat /proc/stat, then... we indeed get a problem.
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Last edited by aCOSwt on Fri Jul 26, 2013 1:41 pm; edited 1 time in total
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ulenrich
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PostPosted: Thu Jul 25, 2013 8:40 pm    Post subject: Reply with quote

My linux-3.10.3rc-bfs just crashed. I rebooted some minutes ago:
Code:
uname -r; cat /proc/uptime ; cat /proc/stat |head -n 1
3.9.11-1001.bd3r
1840.47 3135.84
cpu  20989 68 1679 313584 25977 0 533 0 0 0
This also is an bfs kernel, I remember special code letters in my version string:
b-Bfs, d-DeadlineInOut, 3-is300Hz, r-I forgot about what .config variation I tried some time ago ...
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Last edited by ulenrich on Thu Jul 25, 2013 8:44 pm; edited 1 time in total
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aCOSwt
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PostPosted: Thu Jul 25, 2013 8:43 pm    Post subject: Reply with quote

ulenrich wrote:
My linux-3.10.3rc-bfs just crashed. I rebooted some minutes ago:
Code:
uname -r; cat /proc/uptime ; cat /proc/stat |head -n 1
3.9.11-1001.bd3r
1840.47 [3135.84]
cpu  20989 68 1679 [313584] 25977 0 533 0 0 0
This also is an bfs kernel

That seems much more coherent.
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