From a94f8ca5f95b9943570f0dc8bc48ae7f92e77357 Mon Sep 17 00:00:00 2001
From: Keisuke Umegaki <41987730+keisku@users.noreply.github.com>
Date: Fri, 24 May 2024 07:13:55 +0900
Subject: [PATCH] Fix LRU cache usage (#11)

---
 ebpf/event_handler.go | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/ebpf/event_handler.go b/ebpf/event_handler.go
index 15e2355..4eed871 100644
--- a/ebpf/event_handler.go
+++ b/ebpf/event_handler.go
@@ -13,7 +13,7 @@ import (
 
 	"github.com/cilium/ebpf/ringbuf"
 	"github.com/go-delve/delve/pkg/proc"
-	lru "github.com/hashicorp/golang-lru/v2"
+	"github.com/hashicorp/golang-lru/v2/expirable"
 	"github.com/keisku/gmon/bininfo"
 )
 
@@ -26,7 +26,17 @@ type eventHandler struct {
 
 func (h *eventHandler) run(ctx context.Context) {
 	var event bpfEvent
-	stackIdCache, _ := lru.New[int32, struct{}](16)
+	// To delete stack_addresses that is not used recently.
+	stackIdCache := expirable.NewLRU[int32, struct{}](
+		32, // cache size
+		func(key int32, _ struct{}) {
+			slog.Debug("delete stack_addresses", slog.Int("stack_id", int(key)))
+			if err := h.objs.StackAddresses.Delete(key); err != nil {
+				slog.Debug("Failed to delete stack_addresses", slog.Any("error", err))
+			}
+		},
+		time.Minute, // TTL of each cache entry
+	)
 	for {
 		if err := h.readRecord(ctx, &event); err != nil {
 			if errors.Is(err, ringbuf.ErrClosed) {
@@ -47,13 +57,7 @@ func (h *eventHandler) run(ctx context.Context) {
 			Stack:      stack,
 			Exit:       event.Exit,
 		})
-		contains, _ := stackIdCache.ContainsOrAdd(event.StackId, struct{}{})
-		if !contains {
-			slog.Debug("delete stack_addresses", slog.Int("stack_id", int(event.StackId)))
-			if err := h.objs.StackAddresses.Delete(event.StackId); err != nil {
-				slog.Debug("Failed to delete stack_addresses", slog.Any("error", err))
-			}
-		}
+		_ = stackIdCache.Add(event.StackId, struct{}{})
 	}
 }