Description of problem: CPU usage stats reported in /proc/stat are very erratic. When running steady workload against the system, CPU usage varies between 6% and 100%. Version-Release number of selected component (if applicable): kernel-2.4.20-18.8 How reproducible: Run some steady workload and monitor CPU usage with sar or /proc/stat. Steps to Reproduce: 1. 2. 3. Actual results: With 2.4.20-18.8 kernel: [root@arlx077 root]# sar -u 1 0 Linux 2.4.20-18.8 (arlx077.austin.ibm.com) 07/03/2003 02:42:23 PM CPU %user %nice %system %idle 02:42:24 PM all 0.00 0.00 0.00 100.00 02:42:25 PM all 0.00 0.00 0.00 100.00 02:42:26 PM all 0.00 0.00 0.00 100.00 02:42:27 PM all 13.00 0.00 19.00 68.00 02:42:28 PM all 7.00 0.00 10.00 83.00 02:42:29 PM all 0.00 0.00 10.00 90.00 02:42:30 PM all 0.00 0.00 22.00 78.00 02:42:31 PM all 0.00 0.00 24.00 76.00 02:42:32 PM all 0.00 0.00 12.00 88.00 02:42:33 PM all 3.00 0.00 13.00 84.00 02:42:34 PM all 17.00 0.00 20.00 63.00 02:42:35 PM all 27.00 0.00 42.00 31.00 02:42:36 PM all 56.00 0.00 42.00 2.00 02:42:37 PM all 72.00 0.00 26.00 2.00 02:42:38 PM all 57.00 0.00 42.00 1.00 02:42:39 PM all 35.00 0.00 52.00 13.00 02:42:40 PM all 19.00 0.00 38.00 43.00 02:42:41 PM all 12.00 0.00 16.00 72.00 02:42:42 PM all 2.00 0.00 4.00 94.00 02:42:43 PM all 0.00 0.00 20.00 80.00 02:42:44 PM all 0.00 0.00 29.00 71.00 02:42:45 PM all 0.00 0.00 10.00 90.00 02:42:46 PM all 0.00 0.00 9.00 91.00 02:42:47 PM all 11.00 0.00 14.00 75.00 02:42:48 PM all 28.00 0.00 34.00 38.00 02:42:49 PM all 52.00 0.00 43.00 5.00 02:42:50 PM all 67.00 0.00 33.00 0.00 02:42:51 PM all 56.00 0.00 44.00 0.00 02:42:52 PM all 33.00 0.00 61.00 6.00 02:42:53 PM all 18.00 0.00 49.00 33.00 02:42:54 PM all 9.00 0.00 22.00 69.00 02:42:55 PM all 1.00 0.00 2.00 97.00 02:42:56 PM all 1.00 0.00 16.00 83.00 02:42:57 PM all 0.00 0.00 10.00 90.00 Expected results: With 2.4.18-14 kernel: [root@arlx077 root]# sar -u 1 0 Linux 2.4.18-14 (arlx077.austin.ibm.com) 07/03/2003 02:55:15 PM CPU %user %nice %system %idle 02:55:16 PM all 0.00 0.00 0.00 100.00 02:55:17 PM all 0.00 0.00 0.00 100.00 02:55:18 PM all 0.00 0.00 0.00 100.00 02:55:19 PM all 22.00 0.00 25.00 53.00 02:55:20 PM all 21.00 0.00 24.00 55.00 02:55:21 PM all 25.00 0.00 25.00 50.00 02:55:22 PM all 20.00 0.00 26.00 54.00 02:55:23 PM all 22.00 0.00 24.00 54.00 02:55:24 PM all 22.00 0.00 25.00 53.00 02:55:25 PM all 23.00 0.00 25.00 52.00 02:55:26 PM all 24.00 0.00 25.00 51.00 02:55:27 PM all 23.00 0.00 26.00 51.00 02:55:28 PM all 23.00 0.00 24.00 53.00 02:55:29 PM all 21.00 0.00 27.00 52.00 02:55:30 PM all 23.00 0.00 26.00 51.00 02:55:31 PM all 24.00 0.00 25.00 51.00 02:55:32 PM all 22.00 0.00 23.00 55.00 02:55:33 PM all 24.00 0.00 25.00 51.00 02:55:34 PM all 20.00 0.00 25.00 55.00 02:55:35 PM all 22.00 0.00 23.00 55.00 02:55:36 PM all 22.00 0.00 26.00 52.00 02:55:37 PM all 20.00 0.00 28.00 52.00 Additional info: The only difference between the results shown for the 2.4.20-18.8 kernel and the results for the 2.4.18-14 kernel was the kernel image. Both results come from the same machine with the same basic system install (RH8.0), just different kernel images.
In case this is helpful ... [root@arlx077 root]# cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) Pentium(R) 4 CPU 2.40GHz stepping : 4 cpu MHz : 2390.150 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 4750.85 [root@arlx077 root]#
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