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//go:build linux
// +build linux
package memlimit
import (
"math"
"os"
"path/filepath"
"github.com/containerd/cgroups/v3"
"github.com/containerd/cgroups/v3/cgroup1"
"github.com/containerd/cgroups/v3/cgroup2"
)
const (
cgroupMountPoint = "/sys/fs/cgroup"
)
// FromCgroup returns the memory limit based on the cgroups version on this system.
func FromCgroup() (uint64, error) {
switch cgroups.Mode() {
case cgroups.Legacy:
return FromCgroupV1()
case cgroups.Hybrid:
return FromCgroupHybrid()
case cgroups.Unified:
return FromCgroupV2()
}
return 0, ErrNoCgroup
}
// FromCgroupV1 returns the memory limit from the cgroup v1.
func FromCgroupV1() (uint64, error) {
cg, err := cgroup1.Load(cgroup1.RootPath, cgroup1.WithHiearchy(
cgroup1.SingleSubsystem(cgroup1.Default, cgroup1.Memory),
))
if err != nil {
return 0, err
}
metrics, err := cg.Stat(cgroup1.IgnoreNotExist)
if err != nil {
return 0, err
}
if limit := metrics.GetMemory().GetHierarchicalMemoryLimit(); limit != 0 && limit != getCgroupV1NoLimit() {
return limit, nil
}
return 0, ErrNoLimit
}
func getCgroupV1NoLimit() uint64 {
ps := uint64(os.Getpagesize())
return math.MaxInt64 / ps * ps
}
// FromCgroupHybrid returns the memory limit from the cgroup v1 or v2.
// It checks the cgroup v2 first, and if it fails, it falls back to cgroup v1.
func FromCgroupHybrid() (uint64, error) {
limit, err := fromCgroupV2(filepath.Join(cgroupMountPoint, "unified"))
if err == nil {
return limit, nil
} else if err != ErrNoLimit {
return 0, err
}
return FromCgroupV1()
}
// FromCgroupV2 returns the memory limit from the cgroup v2.
func FromCgroupV2() (uint64, error) {
return fromCgroupV2(cgroupMountPoint)
}
func fromCgroupV2(mountPoint string) (uint64, error) {
path, err := cgroup2.NestedGroupPath("")
if err != nil {
return 0, err
}
m, err := cgroup2.Load(path, cgroup2.WithMountpoint(mountPoint))
if err != nil {
return 0, err
}
stats, err := m.Stat()
if err != nil {
return 0, err
}
if limit := stats.GetMemory().GetUsageLimit(); limit != 0 && limit != math.MaxUint64 {
return limit, nil
}
return 0, ErrNoLimit
}
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