main: Remove Go <= 1.18 memory limits

dcrd.go

@@ -73,35 +73,25 @@ func dcrdMain() error {
 
 	// Block and transaction processing can cause bursty allocations.  This
 	// limits the garbage collector from excessively overallocating during
-	// bursts.  It does this by tweaking the target GC percent and soft memory
-	// limit depending on the version of the Go runtime.
+	// bursts.  It does this by tweaking the soft memory limit.
 	//
-	// Starting with Go 1.19, a soft upper memory limit is imposed that leaves
-	// plenty of headroom for the minimum recommended value and the target GC
-	// percentage is left at the default value to significantly reduce the
-	// number of GC cycles thereby reducing the amount of CPU time spent doing
-	// garbage collection.
+	// A soft upper memory limit is imposed that leaves plenty of headroom
+	// for the minimum recommended value and the target GC percentage is
+	// left at the default value to significantly reduce the number of GC
+	// cycles thereby reducing the amount of CPU time spent doing garbage
+	// collection.
 	//
-	// For versions of Go prior to 1.19, the ability to set a soft upper memory
-	// limit was not available, so the GC percentage is lowered instead which
-	// has the effect of preventing overallocations at the expense of more
-	// frequent GC cycles.
-	//
-	// These values were arrived at with the help of profiling live usage.
-	if limits.SupportsMemoryLimit {
-		// Enforce a soft memory limit for a base amount along with any extra
-		// utxo cache over and above the default max cache size.
-		const memLimitBase = (15 * (1 << 30)) / 10 // 1.5 GiB
-		softMemLimit := int64(memLimitBase)
-		if cfg.UtxoCacheMaxSize > defaultUtxoCacheMaxSize {
-			extra := int64(cfg.UtxoCacheMaxSize) - defaultUtxoCacheMaxSize
-			softMemLimit += extra * (1 << 20)
-		}
-		limits.SetMemoryLimit(softMemLimit)
-		dcrdLog.Infof("Soft memory limit: %s", humanizeBytes(softMemLimit))
-	} else {
-		debug.SetGCPercent(20)
+	// A limit of 1.5 GiB is used as a baseline, with an increase to the
+	// limit when the UTXO cache max size has been increased over the
+	// default.
+	const memLimitBase = (15 * (1 << 30)) / 10 // 1.5 GiB
+	softMemLimit := int64(memLimitBase)
+	if cfg.UtxoCacheMaxSize > defaultUtxoCacheMaxSize {
+		extra := int64(cfg.UtxoCacheMaxSize) - defaultUtxoCacheMaxSize
+		softMemLimit += extra * (1 << 20)
 	}
+	debug.SetMemoryLimit(softMemLimit)
+	dcrdLog.Infof("Soft memory limit: %s", humanizeBytes(softMemLimit))
 
 	// Enable http profile server if requested.  Note that since the server may
 	// be started now or dynamically started and stopped later, the stop call is