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Add kernel 5.9+ version check for MemoryQoS

Browse source 
The check runs only when MemoryQoS feature gate is enabled and
cgroups v2 is in use. It logs a warning but does not block kubelet
startup, since RHEL/LTS kernels may backport the fix without bumping
the version.

Signed-off-by: Sohan Kunkerkar <sohank2602@gmail.com>
This commit is contained in:
Sohan Kunkerkar 2026-03-11 23:50:36 -04:00
parent 757cdd0115
commit c859cb3e64
2 changed files with 22 additions and 4 deletions
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20
cmd/kubelet/app/server.go
View file

@ -63,6 +63,7 @@ import (
utilruntime "k8s.io/apimachinery/pkg/util/runtime"
"k8s.io/apimachinery/pkg/util/sets"
"k8s.io/apimachinery/pkg/util/validation/field"
utilversion "k8s.io/apimachinery/pkg/util/version"
"k8s.io/apimachinery/pkg/util/wait"
genericapiserver "k8s.io/apiserver/pkg/server"
"k8s.io/apiserver/pkg/server/flagz"
@ -120,6 +121,7 @@ import (
"k8s.io/kubernetes/pkg/kubelet/watchdog"
utilfs "k8s.io/kubernetes/pkg/util/filesystem"
"k8s.io/kubernetes/pkg/util/flock"
utilkernel "k8s.io/kubernetes/pkg/util/kernel"
"k8s.io/kubernetes/pkg/util/oom"
"k8s.io/kubernetes/pkg/util/rlimit"
"k8s.io/kubernetes/pkg/volume/util/hostutil"
@ -642,10 +644,20 @@ func run(ctx context.Context, s *options.KubeletServer, kubeDeps *kubelet.Depend
return err
}
// Warn if MemoryQoS enabled with cgroups v1
if utilfeature.DefaultFeatureGate.Enabled(features.MemoryQoS) &&
!kubeletutil.IsCgroup2UnifiedMode() {
logger.Info("Warning: MemoryQoS feature only works with cgroups v2 on Linux, but enabled with cgroups v1")
// Warn about MemoryQoS compatibility issues
if utilfeature.DefaultFeatureGate.Enabled(features.MemoryQoS) {
if !kubeletutil.IsCgroup2UnifiedMode() {
logger.Info("Warning: MemoryQoS feature only works with cgroups v2 on Linux, but enabled with cgroups v1")
} else {
kernelVersion, err := utilkernel.GetVersion()
if err != nil {
logger.Error(err, "Failed to detect kernel version for MemoryQoS compatibility check")
} else if kernelVersion.LessThan(utilversion.MustParseGeneric(utilkernel.MemoryQoSMinKernelVersion)) {
logger.Info("Warning: MemoryQoS memory.high throttling may cause process livelock on older kernels",
"currentKernel", kernelVersion,
"minimumKernel", utilkernel.MemoryQoSMinKernelVersion)
}
}
}
// Obtain Kubelet Lock File
if s.ExitOnLockContention && s.LockFilePath == "" {

6
pkg/util/kernel/constants.go
View file

@ -58,3 +58,9 @@ const TCPReceiveMemoryNamespacedKernelVersion = "4.15"
// TCPTransmitMemoryNamespacedKernelVersion is the kernel version in which net.ipv4.tcp_wmem was namespaced(netns).
// (ref: https://github.com/torvalds/linux/commit/356d1833b638bd465672aefeb71def3ab93fc17d)
const TCPTransmitMemoryNamespacedKernelVersion = "4.15"
// MemoryQoSMinKernelVersion is the minimum kernel version for safe memory.high throttling.
// Kernels older than 5.9 have a livelock bug where processes can get stuck in an infinite
// reclaim loop at the memory.high boundary.
// (ref: https://github.com/torvalds/linux/commit/b3ff92916af3156df27716bb080a407e4caf9085)
const MemoryQoSMinKernelVersion = "5.9"