I'm seeing some strange results from top on CentOS 4.0. When it first starts, it reports low CPU usage. The next refresh (and subsequent) refreshes, it shows high CPU usage. In both cases, there is nothing shown in the process list that is using much CPU. What is causing this?
Here is some truncated output from a single run of "top -b -n 2":
---------------------------------------------------------------------------- -- top - 10:22:02 up 34 days, 14:36, 2 users, load average: 0.98, 0.56, 0.51 Tasks: 116 total, 1 running, 115 sleeping, 0 stopped, 0 zombie Cpu(s): 3.7% us, 0.7% sy, 0.0% ni, 94.2% id, 1.3% wa, 0.0% hi, 0.0% si Mem: 1034676k total, 610804k used, 423872k free, 35796k buffers Swap: 1052248k total, 14220k used, 1038028k free, 314524k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 16412 root 16 0 2280 864 664 R 5.6 0.1 0:00.06 top 1 root 16 0 3148 516 464 S 0.0 0.0 0:01.91 init 2 root RT 0 0 0 0 S 0.0 0.0 0:04.32 migration/0 3 root 34 19 0 0 0 S 0.0 0.0 0:00.34 ksoftirqd/0 4 root RT 0 0 0 0 S 0.0 0.0 0:02.32 migration/1 5 root 34 19 0 0 0 S 0.0 0.0 0:00.39 ksoftirqd/1 6 root 5 -10 0 0 0 S 0.0 0.0 0:00.13 events/0 7 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/1 8 root 5 -10 0 0 0 S 0.0 0.0 0:00.18 khelper 9 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/0
top - 10:22:05 up 34 days, 14:36, 2 users, load average: 0.98, 0.56, 0.51 Tasks: 116 total, 1 running, 115 sleeping, 0 stopped, 0 zombie Cpu(s): 49.1% us, 1.6% sy, 0.0% ni, 48.8% id, 0.2% wa, 0.2% hi, 0.2% si Mem: 1034676k total, 610804k used, 423872k free, 35800k buffers Swap: 1052248k total, 14220k used, 1038028k free, 314520k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 16412 root 17 0 2288 960 748 R 1.6 0.1 0:00.11 top 16052 bowieb 16 0 8288 2232 1812 S 0.3 0.2 0:03.04 sshd 1 root 16 0 3148 516 464 S 0.0 0.0 0:01.91 init 2 root RT 0 0 0 0 S 0.0 0.0 0:04.32 migration/0 3 root 34 19 0 0 0 S 0.0 0.0 0:00.34 ksoftirqd/0 4 root RT 0 0 0 0 S 0.0 0.0 0:02.32 migration/1 5 root 34 19 0 0 0 S 0.0 0.0 0:00.39 ksoftirqd/1 6 root 5 -10 0 0 0 S 0.0 0.0 0:00.13 events/0 7 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/1 8 root 5 -10 0 0 0 S 0.0 0.0 0:00.18 khelper 9 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/0 ---------------------------------------------------------------------------- --
Notice 3.7% usage on the first one and 49.1% usage on the second.
I suspect that top isn't showing me everything. I know that some versions of top had problems with showing proper CPU usage for threaded applications. Is that still a problem with the current version of top?
Bowie