cmd/geth: set default cache to 4096 (#33836)

Mainnet was already overriding --cache to 4096. This PR just makes this
the default.

cmd/geth/main.go

@@ -22,7 +22,6 @@ import (
 	"os"
 	"slices"
 	"sort"
-	"strconv"
 	"time"
 
 	"github.com/ethereum/go-ethereum/accounts"
@@ -316,18 +315,6 @@ func prepare(ctx *cli.Context) {
 	case !ctx.IsSet(utils.NetworkIdFlag.Name):
 		log.Info("Starting Geth on Ethereum mainnet...")
 	}
-	// If we're a full node on mainnet without --cache specified, bump default cache allowance
-	if !ctx.IsSet(utils.CacheFlag.Name) && !ctx.IsSet(utils.NetworkIdFlag.Name) {
-		// Make sure we're not on any supported preconfigured testnet either
-		if !ctx.IsSet(utils.HoleskyFlag.Name) &&
-			!ctx.IsSet(utils.SepoliaFlag.Name) &&
-			!ctx.IsSet(utils.HoodiFlag.Name) &&
-			!ctx.IsSet(utils.DeveloperFlag.Name) {
-			// Nope, we're really on mainnet. Bump that cache up!
-			log.Info("Bumping default cache on mainnet", "provided", ctx.Int(utils.CacheFlag.Name), "updated", 4096)
-			ctx.Set(utils.CacheFlag.Name, strconv.Itoa(4096))
-		}
-	}
 }
 
 // geth is the main entry point into the system if no special subcommand is run.

cmd/utils/flags.go

@@ -491,7 +491,7 @@ var (
 	CacheFlag = &cli.IntFlag{
 		Name:     "cache",
 		Usage:    "Megabytes of memory allocated to internal caching (default = 4096 mainnet full node, 128 light mode)",
-		Value:    1024,
+		Value:    4096,
 		Category: flags.PerfCategory,
 	}
 	CacheDatabaseFlag = &cli.IntFlag{