|Summary:||anomalous user time from clock(3)/times(3)/setitimer(3) on SMP alpha|
|Product:||[Retired] Red Hat Linux||Reporter:||Jeff Johnson <jbj>|
|Component:||kernel||Assignee:||Cristian Gafton <gafton>|
|Status:||CLOSED CURRENTRELEASE||QA Contact:|
|Version:||6.0||CC:||gafton, ken.crandall, michael.waite|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Cloudforms Team:||---||Target Upstream Version:|
Description Jeff Johnson 1999-07-15 16:17:20 UTC
Here's the output, program attached deathstar.support.redhat.com Linux version 2.2.5-24smp (email@example.com) (gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)) #1 SMP Fri Jul 9 16:00:42 EDT 1999 glibc-2.1.1-7 : gettimeofday() reports 9.1871 seconds real time elapsed clock() reports 73435216 cpu time or 73.4352 seconds times() reports 9403 clock ticks or 75240 user and 1 sys itimer reports 9.1831 real time, 73.4759 user, and 9.1850 sys+user glibc-2.1.2-1 : gettimeofday() reports 9.1808 seconds real time elapsed clock() reports 73395200 cpu time or 73.3952 seconds times() reports 9397 clock ticks or 75200 user and 0 sys itimer reports 9.1772 real time, 73.4368 user, and 9.1792 sys+user
Comment 1 Jeff Johnson 1999-07-15 16:24:59 UTC
Note: this problem is present in glibc-2.1.2 (from Ken Crandall).
Comment 2 Jeff Johnson 1999-07-23 09:28:59 UTC
*** Bug 3838 has been marked as a duplicate of this bug. *** 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 3 Jeff Johnson 1999-07-23 09:32:59 UTC
This appears to be a 2.2.5smp kernel bug: the user time returned by the times system call seems to be incorrect.
Comment 4 Cristian Gafton 1999-07-28 07:58:59 UTC
This should be fixed in a later release of the linux kernel, which I am putting out now. There is a kernel-2.2.10-3 now in the tree - can anybody tell me if the problem is still there so that I can get rth on board?