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Improve handling of comounted cpu,cpuacct controllers (#2911)

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* Improve handling of comounted cpu,cpuacct controllers

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>
This commit is contained in:
Brad Davidson 2021-02-09 16:12:58 -08:00 committed by GitHub
parent 41fd27ab56
commit e06119729b
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 40 additions and 26 deletions
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66
pkg/daemons/agent/agent.go
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@ -184,14 +184,11 @@ func addFeatureGate(current, new string) string {
}
func checkCgroups() (kubeletRoot, runtimeRoot string, hasCFS, hasPIDs bool) {
f, err := os.Open("/proc/self/cgroup")
if err != nil {
return "", "", false, false
}
defer f.Close()
cgroupsModeV2 := cgroups.Mode() == cgroups.Unified
v2 := cgroups.Mode() == cgroups.Unified
if v2 {
// For Unified (v2) cgroups we can directly check to see what controllers are mounted
// under the unified hierarchy.
if cgroupsModeV2 {
m, err := cgroupsv2.LoadManager("/sys/fs/cgroup", "/")
if err != nil {
return "", "", false, false
@ -200,33 +197,35 @@ func checkCgroups() (kubeletRoot, runtimeRoot string, hasCFS, hasPIDs bool) {
if err != nil {
return "", "", false, false
}
for _, c := range controllers {
switch c {
case "cpu":
// Intentionally using an expressionless switch to match the logic below
for _, controller := range controllers {
switch {
case controller == "cpu":
hasCFS = true
case "pids":
case controller == "pids":
hasPIDs = true
}
}
}
f, err := os.Open("/proc/self/cgroup")
if err != nil {
return "", "", false, false
}
defer f.Close()
scan := bufio.NewScanner(f)
for scan.Scan() {
parts := strings.Split(scan.Text(), ":")
if len(parts) < 3 {
continue
}
systems := strings.Split(parts[1], ",")
// when v2, systems = {""} (only contains a single empty string)
for _, system := range systems {
if system == "pids" {
hasPIDs = true
} else if system == "cpu" {
p := filepath.Join("/sys/fs/cgroup", parts[1], parts[2], "cpu.cfs_period_us")
if _, err := os.Stat(p); err == nil {
hasCFS = true
}
} else if system == "name=systemd" || v2 {
controllers := strings.Split(parts[1], ",")
// For v1 or hybrid, controller can be a single value {"blkio"}, or a comounted set {"cpu","cpuacct"}
// For v2, controllers = {""} (only contains a single empty string)
for _, controller := range controllers {
switch {
case controller == "name=systemd" || cgroupsModeV2:
// If we detect that we are running under a `.scope` unit with systemd
// we can assume we are being directly invoked from the command line
// and thus need to set our kubelet root to something out of the context
@ -240,10 +239,23 @@ func checkCgroups() (kubeletRoot, runtimeRoot string, hasCFS, hasPIDs bool) {
if i > 0 {
kubeletRoot = "/" + version.Program
}
case controller == "cpu":
// It is common for this to show up multiple times in /sys/fs/cgroup if the controllers are comounted:
// as "cpu" and "cpuacct", symlinked to the actual hierarchy at "cpu,cpuacct". Unfortunately the order
// listed in /proc/self/cgroups may not be the same order used in /sys/fs/cgroup, so this check
// can fail if we use the comma-separated name. Instead, we check for the controller using the symlink.
p := filepath.Join("/sys/fs/cgroup", controller, parts[2], "cpu.cfs_period_us")
if _, err := os.Stat(p); err == nil {
hasCFS = true
}
case controller == "pids":
hasPIDs = true
}
}
}
// If we're running with v1 and didn't find a scope assigned by systemd, we need to create our own root cgroup to avoid
// just inheriting from the parent process. The kubelet will take care of moving us into it when we start it up later.
if kubeletRoot == "" {
// Examine process ID 1 to see if there is a cgroup assigned to it.
// When we are not in a container, process 1 is likely to be systemd or some other service manager.
@ -261,10 +273,12 @@ func checkCgroups() (kubeletRoot, runtimeRoot string, hasCFS, hasPIDs bool) {
if len(parts) < 3 {
continue
}
systems := strings.Split(parts[1], ",")
// when v2, systems = {""} (only contains a single empty string)
for _, system := range systems {
if system == "name=systemd" || v2 {
controllers := strings.Split(parts[1], ",")
// For v1 or hybrid, controller can be a single value {"blkio"}, or a comounted set {"cpu","cpuacct"}
// For v2, controllers = {""} (only contains a single empty string)
for _, controller := range controllers {
switch {
case controller == "name=systemd" || cgroupsModeV2:
last := parts[len(parts)-1]
if last != "/" && last != "/init.scope" {
kubeletRoot = "/" + version.Program