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Date: Wed, 1 Nov 2017 17:01:29 +0800 From: qing hao <v.qingh@...il.com> To: linux-kernel@...r.kernel.org Subject: cpuacct.stat is too much bigger than cpuacct.usage Hello, I found that on kernel linux3.10, 64-bit, not virtual machine, when I attach my process to a newly created cgroup (/sys/fs/cgroup/cpu,cpuacct/p1), the cputime collection of cpuacct.stat and cpuacct.usage have a big difference. Cputime in cpuacct.stat is too much bigger than cpuacct.usage. (I tried on linux4.4, and doesn't has such issue. I searched mailing list, but didn't find related fix.) Is there any explanation, or is this a kernel bug? Which file's CPU time is more accurate that I can trust? I need separated sys time and user time. # cat run.sh #! /bin/bash sudo echo $$ > /sys/fs/cgroup/cpu,cpuacct/p1/tasks MAX=200000 for i in $(seq ${MAX}) do echo "test" > /tmp/p1 rm /tmp/p1 done # cat cpuacct.stat cpuacct.usage user 7756 system 37760 --> utime + stime = 377s + 77s = 454s 360566710120 --> total cputime is 360s # getconf CLK_TCK 100 # pwd /sys/devices/system/cpu # cat present 0-3 # cat online 0-3 Looking forward for you reply. Thanks. -Qing
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