From e4a750b33a0b34f6630ad1ff5067e042cf34ef01 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Geyslan=20Greg=C3=B3rio?= <geyslan@gmail.com>
Date: Fri, 17 Jan 2025 07:42:59 -0300
Subject: [PATCH] perf(controlplane): introduce signal pool

It helps to reduce the stack dynamic growth and the number of
allocations, which is good for performance.
---
 pkg/ebpf/controlplane/controller.go | 34 ++++++++++++++++++++++++++---
 pkg/ebpf/controlplane/signal.go     |  4 ++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/pkg/ebpf/controlplane/controller.go b/pkg/ebpf/controlplane/controller.go
index 2112d52af753..981496054078 100644
--- a/pkg/ebpf/controlplane/controller.go
+++ b/pkg/ebpf/controlplane/controller.go
@@ -3,6 +3,7 @@ package controlplane
 import (
 	"context"
 	"fmt"
+	"sync"
 	"time"
 
 	"github.com/aquasecurity/libbpfgo"
@@ -25,6 +26,7 @@ type Controller struct {
 	lostSignalChan chan uint64
 	bpfModule      *libbpfgo.Module
 	signalBuffer   *libbpfgo.PerfBuffer
+	signalPool     *sync.Pool
 	cgroupManager  *containers.Containers
 	processTree    *proctree.ProcessTree
 	enrichDisabled bool
@@ -43,6 +45,11 @@ func NewController(
 		signalChan:     make(chan []byte, 100),
 		lostSignalChan: make(chan uint64),
 		bpfModule:      bpfModule,
+		signalPool: &sync.Pool{
+			New: func() interface{} {
+				return &signal{}
+			},
+		},
 		cgroupManager:  cgroupManager,
 		processTree:    procTree,
 		enrichDisabled: enrichDisabled,
@@ -69,16 +76,22 @@ func (ctrl *Controller) Run(ctx context.Context) {
 	for {
 		select {
 		case signalData := <-ctrl.signalChan:
-			signal := signal{}
+			signal := ctrl.getSignalFromPool()
+
+			// NOTE: override all the fields of the signal, to avoid any previous data.
 			err := signal.Unmarshal(signalData)
 			if err != nil {
 				logger.Errorw("error unmarshaling signal ebpf buffer", "error", err)
+				ctrl.putSignalInPool(signal)
 				continue
 			}
+
 			err = ctrl.processSignal(signal)
 			if err != nil {
 				logger.Errorw("error processing control plane signal", "error", err)
 			}
+
+			ctrl.putSignalInPool(signal)
 		case lost := <-ctrl.lostSignalChan:
 			logger.Warnw(fmt.Sprintf("Lost %d control plane signals", lost))
 		case <-ctrl.ctx.Done():
@@ -93,8 +106,10 @@ func (ctrl *Controller) Stop() error {
 	return nil
 }
 
+// Private
+
 // processSignal processes a signal from the control plane.
-func (ctrl *Controller) processSignal(signal signal) error {
+func (ctrl *Controller) processSignal(signal *signal) error {
 	switch signal.id {
 	case events.SignalCgroupMkdir:
 		return ctrl.processCgroupMkdir(signal.args)
@@ -111,7 +126,20 @@ func (ctrl *Controller) processSignal(signal signal) error {
 	return nil
 }
 
-// Private
+// getSignalFromPool gets a signal from the pool.
+// signal certainly contains old data, so it must be updated before use.
+func (ctrl *Controller) getSignalFromPool() *signal {
+	// revive:disable:unchecked-type-assertion
+	sig := ctrl.signalPool.Get().(*signal)
+	// revive:enable:unchecked-type-assertion
+
+	return sig
+}
+
+// putSignalInPool puts a signal back in the pool.
+func (ctrl *Controller) putSignalInPool(sig *signal) {
+	ctrl.signalPool.Put(sig)
+}
 
 // debug prints the process tree every 5 seconds (for debugging purposes).
 func (ctrl *Controller) debug(enable bool) {
diff --git a/pkg/ebpf/controlplane/signal.go b/pkg/ebpf/controlplane/signal.go
index da5aa9cea294..33360d82c981 100644
--- a/pkg/ebpf/controlplane/signal.go
+++ b/pkg/ebpf/controlplane/signal.go
@@ -19,7 +19,9 @@ func (sig *signal) Unmarshal(buffer []byte) error {
 	if err != nil {
 		return errfmt.Errorf("failed to decode signal event ID: %v", err)
 	}
+
 	sig.id = events.ID(eventIdUint32)
+
 	var argnum uint8
 	err = ebpfDecoder.DecodeUint8(&argnum)
 	if err != nil {
@@ -33,7 +35,9 @@ func (sig *signal) Unmarshal(buffer []byte) error {
 
 	evtFields := eventDefinition.GetFields()
 	evtName := eventDefinition.GetName()
+
 	sig.args = make([]trace.Argument, len(evtFields))
+
 	err = ebpfDecoder.DecodeArguments(sig.args, int(argnum), evtFields, evtName, sig.id)
 	if err != nil {
 		return errfmt.Errorf("failed to decode signal arguments: %v", err)