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# 58 | cgroup技术:内部创业公司应该独立核算成本
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我们前面说了,容器实现封闭的环境主要靠两种技术,一种是“看起来是隔离”的技术Namespace,另一种是用起来是隔离的技术cgroup。
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上一节我们讲了“看起来隔离“的技术Namespace,这一节我们就来看一下“用起来隔离“的技术cgroup。
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cgroup全称是control group,顾名思义,它是用来做“控制”的。控制什么东西呢?当然是资源的使用了。那它都能控制哪些资源的使用呢?我们一起来看一看。
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首先,cgroup定义了下面的一系列子系统,每个子系统用于控制某一类资源。
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* CPU子系统,主要限制进程的CPU使用率。
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* cpuacct 子系统,可以统计 cgroup 中的进程的 CPU 使用报告。
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* cpuset 子系统,可以为 cgroup 中的进程分配单独的 CPU 节点或者内存节点。
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* memory 子系统,可以限制进程的 Memory 使用量。
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* blkio 子系统,可以限制进程的块设备 IO。
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* devices 子系统,可以控制进程能够访问某些设备。
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* net\_cls 子系统,可以标记 cgroups 中进程的网络数据包,然后可以使用 tc 模块(traffic control)对数据包进行控制。
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* freezer 子系统,可以挂起或者恢复 cgroup 中的进程。
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这么多子系统,你可能要说了,那我们不用都掌握吧?没错,这里面最常用的是对于CPU和内存的控制,所以下面我们详细来说它。
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在容器这一章的第一节,我们讲了,Docker有一些参数能够限制CPU和内存的使用,如果把它落地到cgroup里面会如何限制呢?
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为了验证Docker的参数与cgroup的映射关系,我们运行一个命令特殊的docker run命令,这个命令比较长,里面的参数都会映射为cgroup的某项配置,然后我们运行docker ps,可以看到,这个容器的id为3dc0601189dd。
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```
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docker run -d --cpu-shares 513 --cpus 2 --cpuset-cpus 1,3 --memory 1024M --memory-swap 1234M --memory-swappiness 7 -p 8081:80 testnginx:1
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# docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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3dc0601189dd testnginx:1 "/bin/sh -c 'nginx -…" About a minute ago Up About a minute 0.0.0.0:8081->80/tcp boring_cohen
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```
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在Linux上,为了操作cgroup,有一个专门的cgroup文件系统,我们运行mount命令可以查看。
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```
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# mount -t cgroup
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cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
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cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_prio,net_cls)
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cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
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cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
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cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
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cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpuacct,cpu)
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cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
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cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
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cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
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cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
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cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
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```
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cgroup文件系统多挂载到/sys/fs/cgroup下,通过上面的命令行,我们可以看到我们可以用cgroup控制哪些资源。
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对于CPU的控制,我在这一章的第一节讲过,Docker可以控制cpu-shares、cpus和cpuset。
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我们在/sys/fs/cgroup/下面能看到下面的目录结构。
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```
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drwxr-xr-x 5 root root 0 May 30 17:00 blkio
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lrwxrwxrwx 1 root root 11 May 30 17:00 cpu -> cpu,cpuacct
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lrwxrwxrwx 1 root root 11 May 30 17:00 cpuacct -> cpu,cpuacct
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drwxr-xr-x 5 root root 0 May 30 17:00 cpu,cpuacct
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drwxr-xr-x 3 root root 0 May 30 17:00 cpuset
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drwxr-xr-x 5 root root 0 May 30 17:00 devices
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drwxr-xr-x 3 root root 0 May 30 17:00 freezer
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drwxr-xr-x 3 root root 0 May 30 17:00 hugetlb
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drwxr-xr-x 5 root root 0 May 30 17:00 memory
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lrwxrwxrwx 1 root root 16 May 30 17:00 net_cls -> net_cls,net_prio
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drwxr-xr-x 3 root root 0 May 30 17:00 net_cls,net_prio
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lrwxrwxrwx 1 root root 16 May 30 17:00 net_prio -> net_cls,net_prio
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drwxr-xr-x 3 root root 0 May 30 17:00 perf_event
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drwxr-xr-x 5 root root 0 May 30 17:00 pids
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drwxr-xr-x 5 root root 0 May 30 17:00 systemd
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```
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我们可以想象,CPU的资源控制的配置文件,应该在cpu,cpuacct这个文件夹下面。
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```
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# ls
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cgroup.clone_children cpu.cfs_period_us notify_on_release
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cgroup.event_control cpu.cfs_quota_us release_agent
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cgroup.procs cpu.rt_period_us system.slice
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cgroup.sane_behavior cpu.rt_runtime_us tasks
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cpuacct.stat cpu.shares user.slice
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cpuacct.usage cpu.stat
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cpuacct.usage_percpu docker
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```
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果真,这下面是对CPU的相关控制,里面还有一个路径叫docker。我们进入这个路径。
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```
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]# ls
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cgroup.clone_children
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cgroup.event_control
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cgroup.procs
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cpuacct.stat
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cpuacct.usage
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cpuacct.usage_percpu
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cpu.cfs_period_us
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cpu.cfs_quota_us
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cpu.rt_period_us
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cpu.rt_runtime_us
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cpu.shares
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cpu.stat
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3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd
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notify_on_release
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tasks
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```
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这里面有个很长的id,是我们创建的docker的id。
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```
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[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# ls
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cgroup.clone_children cpuacct.usage_percpu cpu.shares
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cgroup.event_control cpu.cfs_period_us cpu.stat
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cgroup.procs cpu.cfs_quota_us notify_on_release
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cpuacct.stat cpu.rt_period_us tasks
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cpuacct.usage cpu.rt_runtime_us
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```
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在这里,我们能看到cpu.shares,还有一个重要的文件tasks。这里面是这个容器里所有进程的进程号,也即所有这些进程都被这些CPU策略控制。
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```
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[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat tasks
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39487
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39520
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39526
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39527
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39528
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39529
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```
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如果我们查看cpu.shares,里面就是我们设置的513。
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```
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[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat cpu.shares
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513
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```
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另外,我们还配置了cpus,这个值其实是由cpu.cfs\_period\_us和cpu.cfs\_quota\_us共同决定的。cpu.cfs\_period\_us是运行周期,cpu.cfs\_quota\_us是在周期内这些进程占用多少时间。我们设置了cpus为2,代表的意思是,在周期100000微秒的运行周期内,这些进程要占用200000微秒的时间,也即需要两个CPU同时运行一个整的周期。
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```
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[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat cpu.cfs_period_us
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100000
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[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat cpu.cfs_quota_us
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200000
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```
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对于cpuset,也即CPU绑核的参数,在另外一个文件夹里面/sys/fs/cgroup/cpuset,这里面同样有一个docker文件夹,下面同样有docker id 也即3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd文件夹,这里面的cpuset.cpus就是配置的绑定到1、3两个核。
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```
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[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat cpuset.cpus
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1,3
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```
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这一章的第一节我们还讲了Docker可以限制内存的使用量,例如memory、memory-swap、memory-swappiness。这些在哪里控制呢?
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/sys/fs/cgroup/下面还有一个memory路径,控制策略就是在这里面定义的。
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```
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[root@deployer memory]# ls
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cgroup.clone_children memory.memsw.failcnt
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cgroup.event_control memory.memsw.limit_in_bytes
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cgroup.procs memory.memsw.max_usage_in_bytes
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cgroup.sane_behavior memory.memsw.usage_in_bytes
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docker memory.move_charge_at_immigrate
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memory.failcnt memory.numa_stat
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memory.force_empty memory.oom_control
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memory.kmem.failcnt memory.pressure_level
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memory.kmem.limit_in_bytes memory.soft_limit_in_bytes
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memory.kmem.max_usage_in_bytes memory.stat
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memory.kmem.slabinfo memory.swappiness
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memory.kmem.tcp.failcnt memory.usage_in_bytes
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memory.kmem.tcp.limit_in_bytes memory.use_hierarchy
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memory.kmem.tcp.max_usage_in_bytes notify_on_release
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memory.kmem.tcp.usage_in_bytes release_agent
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memory.kmem.usage_in_bytes system.slice
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memory.limit_in_bytes tasks
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memory.max_usage_in_bytes user.slice
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```
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这里面全是对于memory的控制参数,在这里面我们可看到了docker,里面还有容器的id作为文件夹。
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```
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[docker]# ls
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3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd
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cgroup.clone_children
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cgroup.event_control
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cgroup.procs
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memory.failcnt
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memory.force_empty
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memory.kmem.failcnt
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memory.kmem.limit_in_bytes
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memory.kmem.max_usage_in_bytes
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memory.kmem.slabinfo
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memory.kmem.tcp.failcnt
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memory.kmem.tcp.limit_in_bytes
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memory.kmem.tcp.max_usage_in_bytes
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memory.kmem.tcp.usage_in_bytes
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memory.kmem.usage_in_bytes
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memory.limit_in_bytes
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memory.max_usage_in_bytes
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memory.memsw.failcnt
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memory.memsw.limit_in_bytes
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memory.memsw.max_usage_in_bytes
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memory.memsw.usage_in_bytes
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memory.move_charge_at_immigrate
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memory.numa_stat
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memory.oom_control
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memory.pressure_level
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memory.soft_limit_in_bytes
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memory.stat
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memory.swappiness
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memory.usage_in_bytes
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memory.use_hierarchy
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notify_on_release
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tasks
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[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# ls
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cgroup.clone_children memory.memsw.failcnt
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cgroup.event_control memory.memsw.limit_in_bytes
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cgroup.procs memory.memsw.max_usage_in_bytes
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memory.failcnt memory.memsw.usage_in_bytes
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memory.force_empty memory.move_charge_at_immigrate
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memory.kmem.failcnt memory.numa_stat
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memory.kmem.limit_in_bytes memory.oom_control
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memory.kmem.max_usage_in_bytes memory.pressure_level
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memory.kmem.slabinfo memory.soft_limit_in_bytes
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memory.kmem.tcp.failcnt memory.stat
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memory.kmem.tcp.limit_in_bytes memory.swappiness
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memory.kmem.tcp.max_usage_in_bytes memory.usage_in_bytes
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memory.kmem.tcp.usage_in_bytes memory.use_hierarchy
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memory.kmem.usage_in_bytes notify_on_release
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memory.limit_in_bytes tasks
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memory.max_usage_in_bytes
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```
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在docker id的文件夹下面,有一个memory.limit\_in\_bytes,里面配置的就是memory。
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```
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[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat memory.limit_in_bytes
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1073741824
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```
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还有memory.swappiness,里面配置的就是memory-swappiness。
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|
|
|
|
|
```
|
|
|
|
|
[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat memory.swappiness
|
|
|
|
|
7
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
还有就是memory.memsw.limit\_in\_bytes,里面配置的是memory-swap。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat memory.memsw.limit_in_bytes
|
|
|
|
|
1293942784
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
我们还可以看一下tasks文件的内容,tasks里面是容器里面所有进程的进程号。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
[3dc0601189dd218898f31f9526a6cfae83913763a4da59f95ec789c6e030ecfd]# cat tasks
|
|
|
|
|
39487
|
|
|
|
|
39520
|
|
|
|
|
39526
|
|
|
|
|
39527
|
|
|
|
|
39528
|
|
|
|
|
39529
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
至此,我们看到了cgroup对于Docker资源的控制,在用户态是如何表现的。我画了一张图总结一下。
|
|
|
|
|
|
|
|
|
|
![](https://static001.geekbang.org/resource/image/1c/0f/1c762a6283429ff3587a7fc370fc090f.png)
|
|
|
|
|
|
|
|
|
|
在内核中,cgroup是如何实现的呢?
|
|
|
|
|
|
|
|
|
|
首先,在系统初始化的时候,cgroup也会进行初始化,在start\_kernel中,cgroup\_init\_early和cgroup\_init都会进行初始化。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
asmlinkage __visible void __init start_kernel(void)
|
|
|
|
|
{
|
|
|
|
|
......
|
|
|
|
|
cgroup_init_early();
|
|
|
|
|
......
|
|
|
|
|
cgroup_init();
|
|
|
|
|
......
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在cgroup\_init\_early和cgroup\_init中,会有下面的循环。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
for_each_subsys(ss, i) {
|
|
|
|
|
ss->id = i;
|
|
|
|
|
ss->name = cgroup_subsys_name[i];
|
|
|
|
|
......
|
|
|
|
|
cgroup_init_subsys(ss, true);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
#define for_each_subsys(ss, ssid) \
|
|
|
|
|
for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
|
|
|
|
|
(((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
for\_each\_subsys会在cgroup\_subsys数组中进行循环。这个cgroup\_subsys数组是如何形成的呢?
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
|
|
|
|
|
struct cgroup_subsys *cgroup_subsys[] = {
|
|
|
|
|
#include <linux/cgroup_subsys.h>
|
|
|
|
|
};
|
|
|
|
|
#undef SUBSYS
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
SUBSYS这个宏定义了这个cgroup\_subsys数组,数组中的项定义在cgroup\_subsys.h头文件中。例如,对于CPU和内存有下面的定义。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
//cgroup_subsys.h
|
|
|
|
|
|
|
|
|
|
#if IS_ENABLED(CONFIG_CPUSETS)
|
|
|
|
|
SUBSYS(cpuset)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#if IS_ENABLED(CONFIG_CGROUP_SCHED)
|
|
|
|
|
SUBSYS(cpu)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#if IS_ENABLED(CONFIG_CGROUP_CPUACCT)
|
|
|
|
|
SUBSYS(cpuacct)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#if IS_ENABLED(CONFIG_MEMCG)
|
|
|
|
|
SUBSYS(memory)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
根据SUBSYS的定义,SUBSYS(cpu)其实是\[cpu\_cgrp\_id\] = &cpu\_cgrp\_subsys,而SUBSYS(memory)其实是\[memory\_cgrp\_id\] = &memory\_cgrp\_subsys。
|
|
|
|
|
|
|
|
|
|
我们能够找到cpu\_cgrp\_subsys和memory\_cgrp\_subsys的定义。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
cpuset_cgrp_subsys
|
|
|
|
|
struct cgroup_subsys cpuset_cgrp_subsys = {
|
|
|
|
|
.css_alloc = cpuset_css_alloc,
|
|
|
|
|
.css_online = cpuset_css_online,
|
|
|
|
|
.css_offline = cpuset_css_offline,
|
|
|
|
|
.css_free = cpuset_css_free,
|
|
|
|
|
.can_attach = cpuset_can_attach,
|
|
|
|
|
.cancel_attach = cpuset_cancel_attach,
|
|
|
|
|
.attach = cpuset_attach,
|
|
|
|
|
.post_attach = cpuset_post_attach,
|
|
|
|
|
.bind = cpuset_bind,
|
|
|
|
|
.fork = cpuset_fork,
|
|
|
|
|
.legacy_cftypes = files,
|
|
|
|
|
.early_init = true,
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
cpu_cgrp_subsys
|
|
|
|
|
struct cgroup_subsys cpu_cgrp_subsys = {
|
|
|
|
|
.css_alloc = cpu_cgroup_css_alloc,
|
|
|
|
|
.css_online = cpu_cgroup_css_online,
|
|
|
|
|
.css_released = cpu_cgroup_css_released,
|
|
|
|
|
.css_free = cpu_cgroup_css_free,
|
|
|
|
|
.fork = cpu_cgroup_fork,
|
|
|
|
|
.can_attach = cpu_cgroup_can_attach,
|
|
|
|
|
.attach = cpu_cgroup_attach,
|
|
|
|
|
.legacy_cftypes = cpu_files,
|
|
|
|
|
.early_init = true,
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
memory_cgrp_subsys
|
|
|
|
|
struct cgroup_subsys memory_cgrp_subsys = {
|
|
|
|
|
.css_alloc = mem_cgroup_css_alloc,
|
|
|
|
|
.css_online = mem_cgroup_css_online,
|
|
|
|
|
.css_offline = mem_cgroup_css_offline,
|
|
|
|
|
.css_released = mem_cgroup_css_released,
|
|
|
|
|
.css_free = mem_cgroup_css_free,
|
|
|
|
|
.css_reset = mem_cgroup_css_reset,
|
|
|
|
|
.can_attach = mem_cgroup_can_attach,
|
|
|
|
|
.cancel_attach = mem_cgroup_cancel_attach,
|
|
|
|
|
.post_attach = mem_cgroup_move_task,
|
|
|
|
|
.bind = mem_cgroup_bind,
|
|
|
|
|
.dfl_cftypes = memory_files,
|
|
|
|
|
.legacy_cftypes = mem_cgroup_legacy_files,
|
|
|
|
|
.early_init = 0,
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在for\_each\_subsys的循环里面,cgroup\_subsys\[\]数组中的每一个cgroup\_subsys,都会调用cgroup\_init\_subsys,对于cgroup\_subsys对于初始化。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
|
|
|
|
|
{
|
|
|
|
|
struct cgroup_subsys_state *css;
|
|
|
|
|
......
|
|
|
|
|
idr_init(&ss->css_idr);
|
|
|
|
|
INIT_LIST_HEAD(&ss->cfts);
|
|
|
|
|
|
|
|
|
|
/* Create the root cgroup state for this subsystem */
|
|
|
|
|
ss->root = &cgrp_dfl_root;
|
|
|
|
|
css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
|
|
|
|
|
......
|
|
|
|
|
init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
|
|
|
|
|
......
|
|
|
|
|
css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
|
|
|
|
|
init_css_set.subsys[ss->id] = css;
|
|
|
|
|
......
|
|
|
|
|
BUG_ON(online_css(css));
|
|
|
|
|
......
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
cgroup\_init\_subsys里面会做两件事情,一个是调用cgroup\_subsys的css\_alloc函数创建一个cgroup\_subsys\_state;另外就是调用online\_css,也即调用cgroup\_subsys的css\_online函数,激活这个cgroup。
|
|
|
|
|
|
|
|
|
|
对于CPU来讲,css\_alloc函数就是cpu\_cgroup\_css\_alloc。这里面会调用 sched\_create\_group创建一个struct task\_group。在这个结构中,第一项就是cgroup\_subsys\_state,也就是说,task\_group是cgroup\_subsys\_state的一个扩展,最终返回的是指向cgroup\_subsys\_state结构的指针,可以通过强制类型转换变为task\_group。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
struct task_group {
|
|
|
|
|
struct cgroup_subsys_state css;
|
|
|
|
|
|
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
|
|
|
/* schedulable entities of this group on each cpu */
|
|
|
|
|
struct sched_entity **se;
|
|
|
|
|
/* runqueue "owned" by this group on each cpu */
|
|
|
|
|
struct cfs_rq **cfs_rq;
|
|
|
|
|
unsigned long shares;
|
|
|
|
|
|
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
|
atomic_long_t load_avg ____cacheline_aligned;
|
|
|
|
|
#endif
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
struct rcu_head rcu;
|
|
|
|
|
struct list_head list;
|
|
|
|
|
|
|
|
|
|
struct task_group *parent;
|
|
|
|
|
struct list_head siblings;
|
|
|
|
|
struct list_head children;
|
|
|
|
|
|
|
|
|
|
struct cfs_bandwidth cfs_bandwidth;
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在task\_group结构中,有一个成员是sched\_entity,前面我们讲进程调度的时候,遇到过它。它是调度的实体,也即这一个task\_group也是一个调度实体。
|
|
|
|
|
|
|
|
|
|
接下来,online\_css会被调用。对于CPU来讲,online\_css调用的是cpu\_cgroup\_css\_online。它会调用sched\_online\_group->online\_fair\_sched\_group。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
void online_fair_sched_group(struct task_group *tg)
|
|
|
|
|
{
|
|
|
|
|
struct sched_entity *se;
|
|
|
|
|
struct rq *rq;
|
|
|
|
|
int i;
|
|
|
|
|
|
|
|
|
|
for_each_possible_cpu(i) {
|
|
|
|
|
rq = cpu_rq(i);
|
|
|
|
|
se = tg->se[i];
|
|
|
|
|
update_rq_clock(rq);
|
|
|
|
|
attach_entity_cfs_rq(se);
|
|
|
|
|
sync_throttle(tg, i);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在这里面,对于每一个CPU,取出每个CPU的运行队列rq,也取出task\_group的sched\_entity,然后通过attach\_entity\_cfs\_rq将sched\_entity添加到运行队列中。
|
|
|
|
|
|
|
|
|
|
对于内存来讲,css\_alloc函数就是mem\_cgroup\_css\_alloc。这里面会调用 mem\_cgroup\_alloc,创建一个struct mem\_cgroup。在这个结构中,第一项就是cgroup\_subsys\_state,也就是说,mem\_cgroup是cgroup\_subsys\_state的一个扩展,最终返回的是指向cgroup\_subsys\_state结构的指针,我们可以通过强制类型转换变为mem\_cgroup。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
struct mem_cgroup {
|
|
|
|
|
struct cgroup_subsys_state css;
|
|
|
|
|
|
|
|
|
|
/* Private memcg ID. Used to ID objects that outlive the cgroup */
|
|
|
|
|
struct mem_cgroup_id id;
|
|
|
|
|
|
|
|
|
|
/* Accounted resources */
|
|
|
|
|
struct page_counter memory;
|
|
|
|
|
struct page_counter swap;
|
|
|
|
|
|
|
|
|
|
/* Legacy consumer-oriented counters */
|
|
|
|
|
struct page_counter memsw;
|
|
|
|
|
struct page_counter kmem;
|
|
|
|
|
struct page_counter tcpmem;
|
|
|
|
|
|
|
|
|
|
/* Normal memory consumption range */
|
|
|
|
|
unsigned long low;
|
|
|
|
|
unsigned long high;
|
|
|
|
|
|
|
|
|
|
/* Range enforcement for interrupt charges */
|
|
|
|
|
struct work_struct high_work;
|
|
|
|
|
|
|
|
|
|
unsigned long soft_limit;
|
|
|
|
|
|
|
|
|
|
......
|
|
|
|
|
int swappiness;
|
|
|
|
|
......
|
|
|
|
|
/*
|
|
|
|
|
* percpu counter.
|
|
|
|
|
*/
|
|
|
|
|
struct mem_cgroup_stat_cpu __percpu *stat;
|
|
|
|
|
|
|
|
|
|
int last_scanned_node;
|
|
|
|
|
|
|
|
|
|
/* List of events which userspace want to receive */
|
|
|
|
|
struct list_head event_list;
|
|
|
|
|
spinlock_t event_list_lock;
|
|
|
|
|
|
|
|
|
|
struct mem_cgroup_per_node *nodeinfo[0];
|
|
|
|
|
/* WARNING: nodeinfo must be the last member here */
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在cgroup\_init函数中,cgroup的初始化还做了一件很重要的事情,它会调用cgroup\_init\_cftypes(NULL, cgroup1\_base\_files),来初始化对于cgroup文件类型cftype的操作函数,也就是将struct kernfs\_ops \*kf\_ops设置为cgroup\_kf\_ops。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
struct cftype cgroup1_base_files[] = {
|
|
|
|
|
......
|
|
|
|
|
{
|
|
|
|
|
.name = "tasks",
|
|
|
|
|
.seq_start = cgroup_pidlist_start,
|
|
|
|
|
.seq_next = cgroup_pidlist_next,
|
|
|
|
|
.seq_stop = cgroup_pidlist_stop,
|
|
|
|
|
.seq_show = cgroup_pidlist_show,
|
|
|
|
|
.private = CGROUP_FILE_TASKS,
|
|
|
|
|
.write = cgroup_tasks_write,
|
|
|
|
|
},
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static struct kernfs_ops cgroup_kf_ops = {
|
|
|
|
|
.atomic_write_len = PAGE_SIZE,
|
|
|
|
|
.open = cgroup_file_open,
|
|
|
|
|
.release = cgroup_file_release,
|
|
|
|
|
.write = cgroup_file_write,
|
|
|
|
|
.seq_start = cgroup_seqfile_start,
|
|
|
|
|
.seq_next = cgroup_seqfile_next,
|
|
|
|
|
.seq_stop = cgroup_seqfile_stop,
|
|
|
|
|
.seq_show = cgroup_seqfile_show,
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在cgroup初始化完毕之后,接下来就是创建一个cgroup的文件系统,用于配置和操作cgroup。
|
|
|
|
|
|
|
|
|
|
cgroup是一种特殊的文件系统。它的定义如下:
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
struct file_system_type cgroup_fs_type = {
|
|
|
|
|
.name = "cgroup",
|
|
|
|
|
.mount = cgroup_mount,
|
|
|
|
|
.kill_sb = cgroup_kill_sb,
|
|
|
|
|
.fs_flags = FS_USERNS_MOUNT,
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
当我们mount这个cgroup文件系统的时候,会调用cgroup\_mount->cgroup1\_mount。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
|
|
|
|
|
void *data, unsigned long magic,
|
|
|
|
|
struct cgroup_namespace *ns)
|
|
|
|
|
{
|
|
|
|
|
struct super_block *pinned_sb = NULL;
|
|
|
|
|
struct cgroup_sb_opts opts;
|
|
|
|
|
struct cgroup_root *root;
|
|
|
|
|
struct cgroup_subsys *ss;
|
|
|
|
|
struct dentry *dentry;
|
|
|
|
|
int i, ret;
|
|
|
|
|
bool new_root = false;
|
|
|
|
|
......
|
|
|
|
|
root = kzalloc(sizeof(*root), GFP_KERNEL);
|
|
|
|
|
new_root = true;
|
|
|
|
|
|
|
|
|
|
init_cgroup_root(root, &opts);
|
|
|
|
|
|
|
|
|
|
ret = cgroup_setup_root(root, opts.subsys_mask, PERCPU_REF_INIT_DEAD);
|
|
|
|
|
......
|
|
|
|
|
dentry = cgroup_do_mount(&cgroup_fs_type, flags, root,
|
|
|
|
|
CGROUP_SUPER_MAGIC, ns);
|
|
|
|
|
......
|
|
|
|
|
return dentry;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
cgroup被组织成为树形结构,因而有cgroup\_root。init\_cgroup\_root会初始化这个cgroup\_root。cgroup\_root是cgroup的根,它有一个成员kf\_root,是cgroup文件系统的根struct kernfs\_root。kernfs\_create\_root就是用来创建这个kernfs\_root结构的。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask, int ref_flags)
|
|
|
|
|
{
|
|
|
|
|
LIST_HEAD(tmp_links);
|
|
|
|
|
struct cgroup *root_cgrp = &root->cgrp;
|
|
|
|
|
struct kernfs_syscall_ops *kf_sops;
|
|
|
|
|
struct css_set *cset;
|
|
|
|
|
int i, ret;
|
|
|
|
|
|
|
|
|
|
root->kf_root = kernfs_create_root(kf_sops,
|
|
|
|
|
KERNFS_ROOT_CREATE_DEACTIVATED,
|
|
|
|
|
root_cgrp);
|
|
|
|
|
root_cgrp->kn = root->kf_root->kn;
|
|
|
|
|
|
|
|
|
|
ret = css_populate_dir(&root_cgrp->self);
|
|
|
|
|
ret = rebind_subsystems(root, ss_mask);
|
|
|
|
|
......
|
|
|
|
|
list_add(&root->root_list, &cgroup_roots);
|
|
|
|
|
cgroup_root_count++;
|
|
|
|
|
......
|
|
|
|
|
kernfs_activate(root_cgrp->kn);
|
|
|
|
|
......
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
就像在普通文件系统上,每一个文件都对应一个inode,在cgroup文件系统上,每个文件都对应一个struct kernfs\_node结构,当然kernfs\_root作为文件系的根也对应一个kernfs\_node结构。
|
|
|
|
|
|
|
|
|
|
接下来,css\_populate\_dir会调用cgroup\_addrm\_files->cgroup\_add\_file->cgroup\_add\_file,来创建整棵文件树,并且为树中的每个文件创建对应的kernfs\_node结构,并将这个文件的操作函数设置为kf\_ops,也即指向cgroup\_kf\_ops 。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
|
|
|
|
|
struct cftype *cft)
|
|
|
|
|
{
|
|
|
|
|
char name[CGROUP_FILE_NAME_MAX];
|
|
|
|
|
struct kernfs_node *kn;
|
|
|
|
|
......
|
|
|
|
|
kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
|
|
|
|
|
cgroup_file_mode(cft), 0, cft->kf_ops, cft,
|
|
|
|
|
NULL, key);
|
|
|
|
|
......
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
|
|
|
|
|
const char *name,
|
|
|
|
|
umode_t mode, loff_t size,
|
|
|
|
|
const struct kernfs_ops *ops,
|
|
|
|
|
void *priv, const void *ns,
|
|
|
|
|
struct lock_class_key *key)
|
|
|
|
|
{
|
|
|
|
|
struct kernfs_node *kn;
|
|
|
|
|
unsigned flags;
|
|
|
|
|
int rc;
|
|
|
|
|
|
|
|
|
|
flags = KERNFS_FILE;
|
|
|
|
|
|
|
|
|
|
kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG, flags);
|
|
|
|
|
|
|
|
|
|
kn->attr.ops = ops;
|
|
|
|
|
kn->attr.size = size;
|
|
|
|
|
kn->ns = ns;
|
|
|
|
|
kn->priv = priv;
|
|
|
|
|
......
|
|
|
|
|
rc = kernfs_add_one(kn);
|
|
|
|
|
......
|
|
|
|
|
return kn;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
从cgroup\_setup\_root返回后,接下来,在cgroup1\_mount中,要做的一件事情是cgroup\_do\_mount,调用kernfs\_mount真的去mount这个文件系统,返回一个普通的文件系统都认识的dentry。这种特殊的文件系统对应的文件操作函数为kernfs\_file\_fops。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
const struct file_operations kernfs_file_fops = {
|
|
|
|
|
.read = kernfs_fop_read,
|
|
|
|
|
.write = kernfs_fop_write,
|
|
|
|
|
.llseek = generic_file_llseek,
|
|
|
|
|
.mmap = kernfs_fop_mmap,
|
|
|
|
|
.open = kernfs_fop_open,
|
|
|
|
|
.release = kernfs_fop_release,
|
|
|
|
|
.poll = kernfs_fop_poll,
|
|
|
|
|
.fsync = noop_fsync,
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
当我们要写入一个CGroup文件来设置参数的时候,根据文件系统的操作,kernfs\_fop\_write会被调用,在这里面会调用kernfs\_ops的write函数,根据上面的定义为cgroup\_file\_write,在这里会调用cftype的write函数。对于CPU和内存的write函数,有以下不同的定义。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
static struct cftype cpu_files[] = {
|
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
|
|
|
{
|
|
|
|
|
.name = "shares",
|
|
|
|
|
.read_u64 = cpu_shares_read_u64,
|
|
|
|
|
.write_u64 = cpu_shares_write_u64,
|
|
|
|
|
},
|
|
|
|
|
#endif
|
|
|
|
|
#ifdef CONFIG_CFS_BANDWIDTH
|
|
|
|
|
{
|
|
|
|
|
.name = "cfs_quota_us",
|
|
|
|
|
.read_s64 = cpu_cfs_quota_read_s64,
|
|
|
|
|
.write_s64 = cpu_cfs_quota_write_s64,
|
|
|
|
|
},
|
|
|
|
|
{
|
|
|
|
|
.name = "cfs_period_us",
|
|
|
|
|
.read_u64 = cpu_cfs_period_read_u64,
|
|
|
|
|
.write_u64 = cpu_cfs_period_write_u64,
|
|
|
|
|
},
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
static struct cftype mem_cgroup_legacy_files[] = {
|
|
|
|
|
{
|
|
|
|
|
.name = "usage_in_bytes",
|
|
|
|
|
.private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
|
|
|
|
|
.read_u64 = mem_cgroup_read_u64,
|
|
|
|
|
},
|
|
|
|
|
{
|
|
|
|
|
.name = "max_usage_in_bytes",
|
|
|
|
|
.private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
|
|
|
|
|
.write = mem_cgroup_reset,
|
|
|
|
|
.read_u64 = mem_cgroup_read_u64,
|
|
|
|
|
},
|
|
|
|
|
{
|
|
|
|
|
.name = "limit_in_bytes",
|
|
|
|
|
.private = MEMFILE_PRIVATE(_MEM, RES_LIMIT),
|
|
|
|
|
.write = mem_cgroup_write,
|
|
|
|
|
.read_u64 = mem_cgroup_read_u64,
|
|
|
|
|
},
|
|
|
|
|
{
|
|
|
|
|
.name = "soft_limit_in_bytes",
|
|
|
|
|
.private = MEMFILE_PRIVATE(_MEM, RES_SOFT_LIMIT),
|
|
|
|
|
.write = mem_cgroup_write,
|
|
|
|
|
.read_u64 = mem_cgroup_read_u64,
|
|
|
|
|
},
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
如果设置的是cpu.shares,则调用cpu\_shares\_write\_u64。在这里面,task\_group的shares变量更新了,并且更新了CPU队列上的调度实体。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
int sched_group_set_shares(struct task_group *tg, unsigned long shares)
|
|
|
|
|
{
|
|
|
|
|
int i;
|
|
|
|
|
|
|
|
|
|
shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
|
|
|
|
|
|
|
|
|
|
tg->shares = shares;
|
|
|
|
|
for_each_possible_cpu(i) {
|
|
|
|
|
struct rq *rq = cpu_rq(i);
|
|
|
|
|
struct sched_entity *se = tg->se[i];
|
|
|
|
|
struct rq_flags rf;
|
|
|
|
|
|
|
|
|
|
update_rq_clock(rq);
|
|
|
|
|
for_each_sched_entity(se) {
|
|
|
|
|
update_load_avg(se, UPDATE_TG);
|
|
|
|
|
update_cfs_shares(se);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
......
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
但是这个时候别忘了,我们还没有将CPU的文件夹下面的tasks文件写入进程号呢。写入一个进程号到tasks文件里面,按照cgroup1\_base\_files里面的定义,我们应该调用cgroup\_tasks\_write。
|
|
|
|
|
|
|
|
|
|
接下来的调用链为:cgroup\_tasks\_write->\_\_cgroup\_procs\_write->cgroup\_attach\_task-> cgroup\_migrate->cgroup\_migrate\_execute。将这个进程和一个cgroup关联起来,也即将这个进程迁移到这个cgroup下面。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
|
|
|
|
|
{
|
|
|
|
|
struct cgroup_taskset *tset = &mgctx->tset;
|
|
|
|
|
struct cgroup_subsys *ss;
|
|
|
|
|
struct task_struct *task, *tmp_task;
|
|
|
|
|
struct css_set *cset, *tmp_cset;
|
|
|
|
|
......
|
|
|
|
|
if (tset->nr_tasks) {
|
|
|
|
|
do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
|
|
|
|
|
if (ss->attach) {
|
|
|
|
|
tset->ssid = ssid;
|
|
|
|
|
ss->attach(tset);
|
|
|
|
|
}
|
|
|
|
|
} while_each_subsys_mask();
|
|
|
|
|
}
|
|
|
|
|
......
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
每一个cgroup子系统会调用相应的attach函数。而CPU调用的是cpu\_cgroup\_attach-> sched\_move\_task-> sched\_change\_group。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
static void sched_change_group(struct task_struct *tsk, int type)
|
|
|
|
|
{
|
|
|
|
|
struct task_group *tg;
|
|
|
|
|
|
|
|
|
|
tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
|
|
|
|
|
struct task_group, css);
|
|
|
|
|
tg = autogroup_task_group(tsk, tg);
|
|
|
|
|
tsk->sched_task_group = tg;
|
|
|
|
|
|
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
|
|
|
if (tsk->sched_class->task_change_group)
|
|
|
|
|
tsk->sched_class->task_change_group(tsk, type);
|
|
|
|
|
else
|
|
|
|
|
#endif
|
|
|
|
|
set_task_rq(tsk, task_cpu(tsk));
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在sched\_change\_group中设置这个进程以这个task\_group的方式参与调度,从而使得上面的cpu.shares起作用。
|
|
|
|
|
|
|
|
|
|
对于内存来讲,写入内存的限制使用函数mem\_cgroup\_write->mem\_cgroup\_resize\_limit来设置struct mem\_cgroup的memory.limit成员。
|
|
|
|
|
|
|
|
|
|
在进程执行过程中,申请内存的时候,我们会调用handle\_pte\_fault->do\_anonymous\_page()->mem\_cgroup\_try\_charge()。
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
|
|
|
|
|
gfp_t gfp_mask, struct mem_cgroup **memcgp,
|
|
|
|
|
bool compound)
|
|
|
|
|
{
|
|
|
|
|
struct mem_cgroup *memcg = NULL;
|
|
|
|
|
......
|
|
|
|
|
if (!memcg)
|
|
|
|
|
memcg = get_mem_cgroup_from_mm(mm);
|
|
|
|
|
|
|
|
|
|
ret = try_charge(memcg, gfp_mask, nr_pages);
|
|
|
|
|
......
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在mem\_cgroup\_try\_charge中,先是调用get\_mem\_cgroup\_from\_mm获得这个进程对应的mem\_cgroup结构,然后在try\_charge中,根据mem\_cgroup的限制,看是否可以申请分配内存。
|
|
|
|
|
|
|
|
|
|
至此,cgroup对于内存的限制才真正起作用。
|
|
|
|
|
|
|
|
|
|
## 总结时刻
|
|
|
|
|
|
|
|
|
|
内核中cgroup的工作机制,我们在这里总结一下。
|
|
|
|
|
|
|
|
|
|
![](https://static001.geekbang.org/resource/image/c9/c4/c9cc56d20e6a4bac0f9657e6380a96c4.png)
|
|
|
|
|
|
|
|
|
|
第一步,系统初始化的时候,初始化cgroup的各个子系统的操作函数,分配各个子系统的数据结构。
|
|
|
|
|
|
|
|
|
|
第二步,mount cgroup文件系统,创建文件系统的树形结构,以及操作函数。
|
|
|
|
|
|
|
|
|
|
第三步,写入cgroup文件,设置cpu或者memory的相关参数,这个时候文件系统的操作函数会调用到cgroup子系统的操作函数,从而将参数设置到cgroup子系统的数据结构中。
|
|
|
|
|
|
|
|
|
|
第四步,写入tasks文件,将进程交给某个cgroup进行管理,因为tasks文件也是一个cgroup文件,统一会调用文件系统的操作函数进而调用cgroup子系统的操作函数,将cgroup子系统的数据结构和进程关联起来。
|
|
|
|
|
|
|
|
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第五步,对于CPU来讲,会修改scheduled entity,放入相应的队列里面去,从而下次调度的时候就起作用了。对于内存的cgroup设定,只有在申请内存的时候才起作用。
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## 课堂练习
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这里我们用cgroup限制了CPU和内存,如何限制网络呢?给你一个提示tc,请你研究一下。
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欢迎留言和我分享你的疑惑和见解,也欢迎收藏本节内容,反复研读。你也可以把今天的内容分享给你的朋友,和他一起学习和进步。
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