Bug 253103

Summary: /proc/loadavgrt issues weird results
Product: Red Hat Enterprise MRG Reporter: Luis Claudio R. Goncalves <lgoncalv>
Component: realtime-kernelAssignee: Luis Claudio R. Goncalves <lgoncalv>
Status: CLOSED NEXTRELEASE QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: 1.0   
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Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2007-09-10 12:35:18 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Flags
loadavg_fixes_weird_loads.patch
none
Fixes spurious load spikes in /proc/loadavgrt none

Description Luis Claudio R. Goncalves 2007-08-16 22:52:14 UTC 
Description of problem:
We have noticed that values in /proc/loadavgrt are sometimes the real
load and sometimes garbage.

I believe I have already isolated the problem in timer.c->calc_load. But I am
trying the patches along with the ones for bug#253099.

Version-Release number of selected component (if applicable):
2.6.21-31.el5rt
2.6.21-34.el5rt
2.6.21.5-rt20
2.6.23-rc2-rt2

How reproducible:
Easily. More info below.

Steps to Reproduce:
1. Boot a -rt kernel
2. Create some load and observe the dance with:
   watch -n 1 cat /proc/loadavg*
  
Actual results:

Expected results:

Additional info:
        [lclaudio@lab sandbox]$ ls /proc/loadavg*
        /proc/loadavg  /proc/loadavgrt
        [lclaudio@lab sandbox]$ uname -a
        Linux lab.casa 2.6.21-34.el5rt #1 SMP PREEMPT RT Thu Jul 12 15:26:48 EDT
2007 x86_64 x86_64 x86_64 GNU/Linux
        [lclaudio@lab sandbox]$ cat /proc/loadavg*
        4.57 4.90 4.16 3/146 23499
        0.44 0.98 1.78 0/146 23499
        ...
        [lclaudio@lab sandbox]$ cat /proc/loadavg*
        4.65 4.80 4.75 5/144 20720
        23896.04 -898421.23 383170.94 2/144 20720

        [root@neverland ~]# uname -a
        Linux neverland.casa 2.6.21.5-rt20 #2 SMP PREEMPT RT Fri Jul 13 18:31:38
BRT 2007 i686 athlon i386 GNU/Linux
        [root@neverland ~]# cat /proc/loadavg*
        0.16 0.16 0.15 1/184 11240
        344.65 0.38 311.71 0/184 11240

        [williams@torg ~]$ uname -a
        Linux torg 2.6.23-rc2-rt2 #14 SMP PREEMPT RT Tue Aug 7 20:07:31 CDT 2007
x86_64 x86_64 x86_64 GNU/Linux
        [williams@torg ~]$ cat /proc/loadavg*
        0.88 0.76 0.57 1/257 7267
        122947.70 103790.53 -564712.87 0/257 7267
Comment 1 Luis Claudio R. Goncalves 2007-08-17 00:26:14 UTC 
Created attachment 161706 [details]
loadavg_fixes_weird_loads.patch

This patch fixes some glitches that could be responsible for the weird loadavg
spikes we have been observing...
Comment 2 Luis Claudio R. Goncalves 2007-08-24 14:39:41 UTC 
Created attachment 172421 [details]
Fixes spurious load spikes in /proc/loadavgrt

This patch is better cooked than the earlier one.
Comment 3 Luis Claudio R. Goncalves 2007-09-10 12:35:18 UTC 
Patch added to kernel-rt-2.6.21-37.el5rt, soon to be in the rt partners repo.