(see man 2 times on how these fields are supposed to be interpreted). (small tool to convert is at procstat, assumes HZ=100) in "ticks")įield 16: cutime (utime sum for children - waited-for and "ignored"?)įield 17: cstime (stime sum for children)įield 22: start_time: in jiffies, need to compare to uptime. in 2.6.9, (starting at 1=pid, 2=(cmd).):įield 14 is utime, user space (converted via jiffies_to_clock_t(), i.e. proc/pid/stat is filled out by fs/proc/array.c:do_task_stat(), see there for the format. He has a program to translate the LSF accounting logs, see /afs/cern.ch/user/u/uschwick/Programming/LSF/AnaLsbAcct/ Ulrich already filters abnormal CPU time from the site statistics due to this bug. If the CPU time exceeds (wherever this is configured), the proccess is killed via SIGXCPU/signal24 (CPU time limit exceeded), this shold drop a core.Ĭentral LSF accounting is collected in /afs/cern.ch/project/lsf/7.0/mnt/batch/work/batch/acct. It reads /proc/PID/stat regularly, and summarizes the information into /tmp/. On the LSF side, the process responsible per machine is called "pim". On investigation, it turned out that these jobs could not have accumulated that much CPU time - in other words, the per-process statistics under /proc/PID/stat are corrupted.įiled with Red Hat as IT 127884, July 07. When I now sum up the values for all processes and compare it to the overall calculated CPU usage, I receive a slightly higher value for the aggregated value most of the time (although the values are quite close for all different CPU loads).Ĭan anyone explain to me, what's the reason for that? Are there any CPU resources that are used by more than one process and thus accounted twice or more in my accumlation? Or am I simply missing something here? I can not find any further hint in the Linux man page for the proc file system ( ) as well.FIO-Fs has reported issued with LSF killing jobs due to them exceeding the CPU time limit. When I now calculate this sum and divide it by the total amount of jiffies in the analyzed interval, I would assume the formula for one process to be processCPUUsage = ((process_utime_aft - process_utime_bef) + (process_stime_aft - process_stime_bef)) /
#Cpu utime stime how to#
((user_aft - user_bef) + (nice_aft - nice_bef) + (system_aft - system_bef) + (idle_aft - idle_bef)) * 100 %Īccording to How to calculate the CPU usage of a process by PID in Linux from C? the used jiffies for a single process can be calculated by adding utime and stime from /proc/$/stat (column 14 and 15 in this file). The formula would be totalCPUUsage = ((user_aft - user_bef) + (nice_aft - nice_bef) + (system_aft - system_bef)) / If you now sample the values at two points in time and compare the values for user, nice, system and idle at the two time points, you can calculate the average CPU usage in this interval. For now the CPU I am using is multi-cored (2 cores).Īccording to How to determine CPU and memory consumption from inside a process? it is possible to calculate all "jiffies" available in the system since startup using the values for "cpu" in /proc/stat. My assumption would be that the sum of all process CPU times would be equal to the total value for the whole CPU. The programm should be designed and implemented in C++. I need to calculate the overall CPU usage of my Linux device over some time (1-5 seconds) and a list of processes with their respective CPU usage times.
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