Bug 3838 - cpu time is reported incorrectly
cpu time is reported incorrectly
Status: CLOSED DUPLICATE of bug 4056
Product: Red Hat Linux
Classification: Retired
Component: time (Show other bugs)
6.0
alpha Linux
high Severity medium
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Assigned To: Preston Brown
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Depends On:
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Reported: 1999-06-30 16:53 EDT by michael.waite
Modified: 2008-05-01 11:37 EDT (History)
0 users

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Doc Type: Bug Fix
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Last Closed: 1999-07-23 05:28:48 EDT
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Description michael.waite 1999-06-30 16:53:18 EDT
There seems to be a problem with process CPU time display on
Linux Alpha systems.  The process CPU
time increments MUCH faster than wall clock time.  The CPU
time seems to be about 8 to 10 times faster
than wall clock time.  You can see this with either a "w"
display or a "top" display.  For example:

[hibbert@spe85 ~]$ w
Unknown HZ value! (2048) Assume 1024.
  3:47pm  up 38 min,  5 users,  load average: 1.85, 1.27,
0.73
USER     TTY      FROM              LOGIN@   IDLE   JCPU
PCPU  WHAT
root     tty1     -                 3:09pm  0.00s  1.02s
0.78s  talk cnbc
root     tty2     -                 3:39pm  3:29   0.27s
0.14s  -bash
cnbc     pts/0    VIM.BOLTZ.CS.CMU  3:29pm  0.00s  7.03s
0.55s  talk root@spe85
hibbert  pts/1    tnt1-159.mtco.co  3:44pm  1:55  15:12
15:11   ./setiathome
hibbert  pts/2    tnt1-159.mtco.co  3:45pm  0.00s  0.43s
0.06s  w

Note that the first hibbert process has been logged in for
only about 2 minutes, yet has used 15 minutes of
CPU time.  I know Alpha's are fast, but I didn't think they
could bend time!   This bug does not appear to
be a problem for the Proliant Intel based system.

I have been trying to track down this problem.  I suspect
there is a system function that convers CPU ticks
to seconds that is assuming the Alpha is using the common PC
interval clock rate of 100/second rather than
the 1K/second rate that most Alpha's actually use.   I have
not been able to locate the source code for the
"w" program to see what function calls it uses to convert
the time.
Comment 1 Jeff Johnson 1999-07-23 05:28:59 EDT
*** This bug has been marked as a duplicate of 4056 ***

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