使用cgroup限制线程对CPU使用
利用CPU的cgroup sysfs接口，在/sys/fs/cgroup/cpu下创建测试目录：
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| root@m1:/sys/fs/cgroup/cpu# pwd
/sys/fs/cgroup/cpu
root@m1:/sys/fs/cgroup/cpu# mkdir my_test
root@m1:/sys/fs/cgroup/cpu# cd my_test/
root@m1:/sys/fs/cgroup/cpu/my_test# ls
cgroup.clone_children cpuacct.usage_all cpuacct.usage_sys cpu.shares notify_on_release
cgroup.procs cpuacct.usage_percpu cpuacct.usage_user cpu.stat tasks
cpuacct.stat cpuacct.usage_percpu_sys cpu.cfs_period_us cpu.uclamp.max
cpuacct.usage cpuacct.usage_percpu_user cpu.cfs_quota_us cpu.uclamp.min
root@m1:/sys/fs/cgroup/cpu/my_test# cat cpu.cfs_period_us
100000
root@m1:/sys/fs/cgroup/cpu/my_test# cat cpu.cfs_quota_us
-1
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写一个死循环的demo(PID是3818875)，htop查看这个demo跑起来后，对应的CPU占用率为100%：
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| 1 [ 0.0%] Tasks: 138, 464 thr; 2 running
2 [| 0.7%] Load average: 0.97 0.45 0.22
3 [| 0.7%] Uptime: 7 days, 10:12:34
4 [||||||||||||||||||||||||||||||||||||||||||100.0%]
Mem[|||||||||||||||||||||||||||||||||||||1.23G/7.75G]
Swp[||| 111M/2.00G]
PID USER PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command
3818875 sherlock 20 0 1788 432 368 R 99.7 0.0 1:59.92 ./a.out
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把PID写入测试目录的tasks文件，并把cpu.cfs_period_us一半的数值写入到cpu.cfs_quota_us，
这个表示在cpu.cfs_period_us的时间内只容许对应线程运行cpu.cfs_quota_us时间。观察
htop发现，demon死循环线程的CPU占用率大概将为50%。
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| root@m1:/sys/fs/cgroup/cpu/my_test# echo 3818875 > tasks
root@m1:/sys/fs/cgroup/cpu/my_test# echo 50000 > cpu.cfs_quota_us
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| 1 [ 0.0%] Tasks: 138, 464 thr; 2 running
2 [| 0.7%] Load average: 0.75 0.54 0.28
3 [| 0.7%] Uptime: 7 days, 10:14:10
4 [||||||||||||||||||||||||| 51.0%]
Mem[|||||||||||||||||||||||||||||||||||||1.23G/7.75G]
Swp[||| 111M/2.00G]
PID USER PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command
3818875 sherlock 20 0 1788 432 368 R 49.5 0.0 3:21.22 ./a.out
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基本逻辑
todo: …
代码分析
todo: …
