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[v1.2 backport] Memory optimizations: remove BTF and kallsyms caches #3036

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merged 2 commits into from
Oct 23, 2024
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[v1.2 backport] Memory optimizations: remove BTF and kallsyms caches #3036

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ce41876
[ksyms] Do not cache ksyms to reduce memory consumption
tpapagian Sep 20, 2024
cc70591
[btf] Flush kernel spec (BTF) after loading a sensor
tpapagian Sep 20, 2024
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4 changes: 4 additions & 0 deletions pkg/bpf/detect.go
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Original file line number Diff line number Diff line change
Expand Up @@ -422,6 +422,10 @@ func HasMissedStatsKprobeMulti() bool {
}

func LogFeatures() string {
// once we have detected all features, flush the BTF spec
// we cache all values so calling again a Has* function will
// not load the BTF again
defer ebtf.FlushKernelSpec()
return fmt.Sprintf("override_return: %t, buildid: %t, kprobe_multi: %t, uprobe_multi %t, fmodret: %t, fmodret_syscall: %t, signal: %t, large: %t, link_pin: %t, lsm: %t, missed_stats_kprobe_multi: %t, missed_stats_kprobe: %t",
HasOverrideHelper(), HasBuildId(), HasKprobeMulti(), HasUprobeMulti(),
HasModifyReturn(), HasModifyReturnSyscall(), HasSignalHelper(), HasProgramLargeSize(),
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12 changes: 1 addition & 11 deletions pkg/ksyms/ksyms.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11,25 +11,15 @@ import (
"sort"
"strconv"
"strings"
"sync"

"github.com/cilium/tetragon/pkg/logger"
"github.com/cilium/tetragon/pkg/option"

lru "github.com/hashicorp/golang-lru/v2"
)

var (
kernelSymbols *Ksyms
setKernelSymbols sync.Once
)

func KernelSymbols() (*Ksyms, error) {
var err error
setKernelSymbols.Do(func() {
kernelSymbols, err = NewKsyms(option.Config.ProcFS)
})
return kernelSymbols, err
return NewKsyms(option.Config.ProcFS)
}

type ksym struct {
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4 changes: 4 additions & 0 deletions pkg/sensors/load.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ import (
"strings"

"github.com/cilium/ebpf"
"github.com/cilium/ebpf/btf"
cachedbtf "github.com/cilium/tetragon/pkg/btf"
"github.com/cilium/tetragon/pkg/kernels"
"github.com/cilium/tetragon/pkg/logger"
Expand Down Expand Up @@ -115,6 +116,9 @@ func (s *Sensor) Load(bpfDir string) error {
progsAdd(s.Progs)
AllMaps = append(AllMaps, s.Maps...)

// cleanup the BTF once we have loaded all sensor's program
btf.FlushKernelSpec()

l.WithField("sensor", s.Name).Infof("Loaded BPF maps and events for sensor successfully")
s.Loaded = true
return nil
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5 changes: 5 additions & 0 deletions pkg/sensors/program/loader.go
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Expand Up @@ -913,6 +913,11 @@ func doLoadProgram(

load.Prog = prog

// in KernelTypes, we use a non-standard BTF which is possibly annotated with symbols
// from kernel modules. At this point we don't need that anymore, so we can release
// the memory from it.
load.KernelTypes = nil

// Copy the loaded collection before it's destroyed
if KeepCollection {
return copyLoadedCollection(coll)
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