address comments

cmd/utils/flags.go

@@ -24,11 +24,13 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"math"
 	"math/big"
 	"net"
 	"net/http"
 	"os"
 	"path/filepath"
+	godebug "runtime/debug"
 	"strconv"
 	"strings"
 	"time"
@@ -74,6 +76,7 @@ import (
 	"github.com/ethereum/go-ethereum/triedb/hashdb"
 	"github.com/ethereum/go-ethereum/triedb/pathdb"
 	pcsclite "github.com/gballet/go-libpcsclite"
+	gopsutil "github.com/shirou/gopsutil/mem"
 	"github.com/urfave/cli/v2"
 )
 
@@ -1575,18 +1578,38 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 	setRequiredBlocks(ctx, cfg)
 	setLes(ctx, cfg)
 
+	// Cap the cache allowance and tune the garbage collector
+	mem, err := gopsutil.VirtualMemory()
+	if err == nil {
+		if 32<<(^uintptr(0)>>63) == 32 && mem.Total > 2*1024*1024*1024 {
+			log.Warn("Lowering memory allowance on 32bit arch", "available", mem.Total/1024/1024, "addressable", 2*1024)
+			mem.Total = 2 * 1024 * 1024 * 1024
+		}
+		allowance := int(mem.Total / 1024 / 1024 / 3)
+		if cache := ctx.Int(CacheFlag.Name); cache > allowance {
+			log.Warn("Sanitizing cache to Go's GC limits", "provided", cache, "updated", allowance)
+			ctx.Set(CacheFlag.Name, strconv.Itoa(allowance))
+		}
+	}
+	// Ensure Go's GC ignores the database cache for trigger percentage
+	cache := ctx.Int(CacheFlag.Name)
+	gogc := math.Max(20, math.Min(100, 100/(float64(cache)/1024)))
+
+	log.Debug("Sanitizing Go's GC trigger", "percent", int(gogc))
+	godebug.SetGCPercent(int(gogc))
+
 	if ctx.IsSet(SyncTargetFlag.Name) {
 		cfg.SyncMode = ethconfig.FullSync // dev sync target forces full sync
 	} else if ctx.IsSet(SyncModeFlag.Name) {
 		value := ctx.String(SyncModeFlag.Name)
-		if err := cfg.SyncMode.UnmarshalText([]byte(value)); err != nil {
+		if err = cfg.SyncMode.UnmarshalText([]byte(value)); err != nil {
 			Fatalf("--%v: %v", SyncModeFlag.Name, err)
 		}
 	}
 
 	if ctx.IsSet(ChainHistoryFlag.Name) {
 		value := ctx.String(ChainHistoryFlag.Name)
-		if err := cfg.HistoryMode.UnmarshalText([]byte(value)); err != nil {
+		if err = cfg.HistoryMode.UnmarshalText([]byte(value)); err != nil {
 			Fatalf("--%s: %v", ChainHistoryFlag.Name, err)
 		}
 	}

internal/debug/api.go

@@ -238,6 +238,9 @@ func (*HandlerT) SetGCPercent(v int) int {
 }
 
 // SetMemoryLimit sets the GOMEMLIMIT for the process. It returns the previous limit.
+// Note:
+//   - Geth also allocates memory off-heap, particularly for fastCache and Pebble, which can be non-trivial (a few gigabytes by default).
+//   - Setting the limit too low will cause Geth to become unresponsive.
 func (*HandlerT) SetMemoryLimit(limit int64) int64 {
 	return debug.SetMemoryLimit(limit)
 }