cmd/geth: cap cache allowance

cmd/geth/main.go

@@ -19,12 +19,16 @@ package main
 
 import (
 	"fmt"
+	"math"
 	"os"
 	"runtime"
+	godebug "runtime/debug"
 	"sort"
+	"strconv"
 	"strings"
 	"time"
 
+	"github.com/elastic/gosigar"
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/cmd/utils"
@@ -188,6 +192,22 @@ func init() {
 		if err := debug.Setup(ctx); err != nil {
 			return err
 		}
+		// Cap the cache allowance and tune the garbage colelctor
+		var mem gosigar.Mem
+		if err := mem.Get(); err == nil {
+			allowance := int(mem.Total / 1024 / 1024 / 3)
+			if cache := ctx.GlobalInt(utils.CacheFlag.Name); cache > allowance {
+				log.Warn("Sanitizing cache to Go's GC limits", "provided", cache, "updated", allowance)
+				ctx.GlobalSet(utils.CacheFlag.Name, strconv.Itoa(allowance))
+			}
+		}
+		// Ensure Go's GC ignores the database cache for trigger percentage
+		cache := ctx.GlobalInt(utils.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))
+
 		// Start system runtime metrics collection
 		go metrics.CollectProcessMetrics(3 * time.Second)