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pkg/policyfilter: optimize inner policy maps memory usage #4340

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b03c640
pkg/policyfilter: optimize inner policy maps memory usage
kyledong-suse Nov 13, 2025
100c6e6
chore: add user configurable flag for policy filter inner maps
kyledong-suse Nov 17, 2025
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1 change: 1 addition & 0 deletions docs/content/en/docs/reference/helm-chart.md
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3 changes: 3 additions & 0 deletions docs/data/tetragon_flags.yaml
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1 change: 1 addition & 0 deletions install/kubernetes/tetragon/README.md
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3 changes: 3 additions & 0 deletions install/kubernetes/tetragon/templates/tetragon_configmap.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,9 @@ data:
{{- if .Values.tetragon.enablePolicyFilterDebug }}
enable-policy-filter-debug: "true"
{{- end }}
{{- if .Values.tetragon.enablePolicyFilterNoPrealloc }}
enable-policy-filter-no-prealloc: "true"
{{- end }}
{{- if .Values.tetragon.enableMsgHandlingLatency }}
enable-msg-handling-latency: "true"
{{- end }}
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2 changes: 2 additions & 0 deletions install/kubernetes/tetragon/values.yaml
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Expand Up @@ -206,6 +206,8 @@ tetragon:
enablePolicyFilterCgroupMap: false
# -- Enable policy filter debug messages.
enablePolicyFilterDebug: false
# -- Enable BPF_F_NO_PREALLOC flag for policy filter inner maps.
enablePolicyFilterNoPrealloc: false
# -- Enable latency monitoring in message handling
enableMsgHandlingLatency: false
healthGrpc:
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7 changes: 4 additions & 3 deletions pkg/option/config.go
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Expand Up @@ -92,9 +92,10 @@ type config struct {

ReleasePinned bool

EnablePolicyFilter bool
EnablePolicyFilterCgroupMap bool
EnablePolicyFilterDebug bool
EnablePolicyFilter bool
EnablePolicyFilterCgroupMap bool
EnablePolicyFilterDebug bool
EnablePolicyFilterNoPrealloc bool

EnablePidSetFilter bool

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9 changes: 6 additions & 3 deletions pkg/option/flags.go
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Expand Up @@ -93,9 +93,10 @@ const (

KeyReleasePinnedBPF = "release-pinned-bpf"

KeyEnablePolicyFilter = "enable-policy-filter"
KeyEnablePolicyFilterCgroupMap = "enable-policy-filter-cgroup-map"
KeyEnablePolicyFilterDebug = "enable-policy-filter-debug"
KeyEnablePolicyFilter = "enable-policy-filter"
KeyEnablePolicyFilterCgroupMap = "enable-policy-filter-cgroup-map"
KeyEnablePolicyFilterDebug = "enable-policy-filter-debug"
KeyEnablePolicyFilterNoPrealloc = "enable-policy-filter-no-prealloc"

KeyEnablePidSetFilter = "enable-pid-set-filter"

Expand Down Expand Up @@ -237,6 +238,7 @@ func ReadAndSetFlags() error {
Config.EnablePolicyFilter = viper.GetBool(KeyEnablePolicyFilter)
Config.EnablePolicyFilterCgroupMap = viper.GetBool(KeyEnablePolicyFilterCgroupMap)
Config.EnablePolicyFilterDebug = viper.GetBool(KeyEnablePolicyFilterDebug)
Config.EnablePolicyFilterNoPrealloc = viper.GetBool(KeyEnablePolicyFilterNoPrealloc)
Config.EnableMsgHandlingLatency = viper.GetBool(KeyEnableMsgHandlingLatency)

Config.EnablePidSetFilter = viper.GetBool(KeyEnablePidSetFilter)
Expand Down Expand Up @@ -441,6 +443,7 @@ func AddFlags(flags *pflag.FlagSet) {
flags.Bool(KeyEnablePolicyFilter, false, "Enable policy filter code")
flags.Bool(KeyEnablePolicyFilterCgroupMap, false, "Enable cgroup mappings for policy filter maps")
flags.Bool(KeyEnablePolicyFilterDebug, false, "Enable policy filter debug messages")
flags.Bool(KeyEnablePolicyFilterNoPrealloc, false, "Enable BPF_F_NO_PREALLOC flag for policy filter inner maps")

// Provide option to enable the pidSet export filters.
flags.Bool(KeyEnablePidSetFilter, false, "Enable pidSet export filters. Not recommended for production use")
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10 changes: 10 additions & 0 deletions pkg/policyfilter/map.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ import (

"github.com/cilium/tetragon/pkg/bpf"
"github.com/cilium/tetragon/pkg/config"
"github.com/cilium/tetragon/pkg/option"
)

const (
Expand All @@ -39,6 +40,11 @@ func openMap(spec *ebpf.CollectionSpec, mapName string, innerMaxEntries uint32)
// inserting a different size of inner-map, but for older kernels, we
// fix the spec here.
policyMapSpec.InnerMap.MaxEntries = innerMaxEntries
if option.Config.EnablePolicyFilterNoPrealloc {
policyMapSpec.InnerMap.Flags |= bpf.BPF_F_NO_PREALLOC
} else {
policyMapSpec.InnerMap.Flags &^= bpf.BPF_F_NO_PREALLOC
}

ret, err := ebpf.NewMap(policyMapSpec)
if err != nil {
Expand Down Expand Up @@ -185,6 +191,10 @@ func (m PfMap) newPolicyMap(polID PolicyID, cgIDs []CgroupID) (polMap, error) {
MaxEntries: uint32(polMapSize),
}

if option.Config.EnablePolicyFilterNoPrealloc {
innerSpec.Flags = bpf.BPF_F_NO_PREALLOC
}

inner, err := ebpf.NewMap(innerSpec)
if err != nil {
return polMap{}, fmt.Errorf("failed to create policy (id=%d) map: %w", polID, err)
Expand Down
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