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cgroups.go (2035B)

      1 //go:build linux
      2 // +build linux
      3 
      4 package memlimit
      5 
      6 import (
      7 	"path/filepath"
      8 
      9 	"github.com/containerd/cgroups/v3"
     10 	"github.com/containerd/cgroups/v3/cgroup1"
     11 	"github.com/containerd/cgroups/v3/cgroup2"
     12 )
     13 
     14 const (
     15 	cgroupMountPoint = "/sys/fs/cgroup"
     16 )
     17 
     18 // FromCgroup returns the memory limit based on the cgroups version on this system.
     19 func FromCgroup() (uint64, error) {
     20 	switch cgroups.Mode() {
     21 	case cgroups.Legacy:
     22 		return FromCgroupV1()
     23 	case cgroups.Hybrid:
     24 		return fromCgroupHybrid()
     25 	case cgroups.Unified:
     26 		return FromCgroupV2()
     27 	}
     28 	return 0, ErrNoCgroup
     29 }
     30 
     31 // FromCgroupV1 returns the memory limit from the cgroup v1.
     32 func FromCgroupV1() (uint64, error) {
     33 	cg, err := cgroup1.Load(cgroup1.RootPath, cgroup1.WithHiearchy(
     34 		cgroup1.SingleSubsystem(cgroup1.Default, cgroup1.Memory),
     35 	))
     36 	if err != nil {
     37 		return 0, err
     38 	}
     39 
     40 	metrics, err := cg.Stat(cgroup1.IgnoreNotExist)
     41 	if err != nil {
     42 		return 0, err
     43 	}
     44 
     45 	if limit := metrics.GetMemory().GetHierarchicalMemoryLimit(); limit != 0 {
     46 		return limit, nil
     47 	}
     48 
     49 	return 0, ErrNoLimit
     50 }
     51 
     52 // fromCgroupHybrid returns the memory limit from the cgroup v1 or v2.
     53 // It checks the cgroup v2 first, and if it fails, it falls back to cgroup v1.
     54 // TODO: make this function public in the next minor version.
     55 func fromCgroupHybrid() (uint64, error) {
     56 	limit, err := fromCgroupV2(filepath.Join(cgroupMountPoint, "unified"))
     57 	if err == nil {
     58 		return limit, nil
     59 	} else if err != ErrNoLimit {
     60 		return 0, err
     61 	}
     62 
     63 	return FromCgroupV1()
     64 }
     65 
     66 // FromCgroupV2 returns the memory limit from the cgroup v2.
     67 func FromCgroupV2() (uint64, error) {
     68 	return fromCgroupV2(cgroupMountPoint)
     69 }
     70 
     71 func fromCgroupV2(mountPoint string) (uint64, error) {
     72 	path, err := cgroup2.NestedGroupPath("")
     73 	if err != nil {
     74 		return 0, err
     75 	}
     76 
     77 	m, err := cgroup2.Load(path, cgroup2.WithMountpoint(mountPoint))
     78 	if err != nil {
     79 		return 0, err
     80 	}
     81 
     82 	stats, err := m.Stat()
     83 	if err != nil {
     84 		return 0, err
     85 	}
     86 
     87 	if limit := stats.GetMemory().GetUsageLimit(); limit != 0 {
     88 		return limit, nil
     89 	}
     90 
     91 	return 0, ErrNoLimit
     92 }