diff --git a/server/pse/pse_darwin.go b/server/pse/pse_darwin.go
index b00f1e00f6..7fd26b15c3 100644
--- a/server/pse/pse_darwin.go
+++ b/server/pse/pse_darwin.go
@@ -1,4 +1,4 @@
-// Copyright 2015-2018 The NATS Authors
+// Copyright 2015-2021 The NATS Authors
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -13,22 +13,74 @@
 
 package pse
 
+// On macs after some studying it seems that typical tools like ps and activity monitor report MaxRss and not
+// current RSS. I wrote some C code to pull the real RSS and although it does not go down very often, when it does
+// that is not reflected in the typical tooling one might compare us to, so we can skip cgo and just use rusage imo.
+// We also do not use virtual memory in the upper layers at all, so ok to skip since rusage does not report vss.
+
 import (
-	"fmt"
-	"os"
-	"os/exec"
+	"math"
+	"sync"
+	"syscall"
+	"time"
 )
 
-// ProcUsage returns CPU usage
-func ProcUsage(pcpu *float64, rss, vss *int64) error {
-	pidStr := fmt.Sprintf("%d", os.Getpid())
-	out, err := exec.Command("ps", "o", "pcpu=,rss=,vsz=", "-p", pidStr).Output()
-	if err != nil {
-		*rss, *vss = -1, -1
-		return fmt.Errorf("ps call failed:%v", err)
+type lastUsage struct {
+	sync.Mutex
+	last time.Time
+	cpu  time.Duration
+	rss  int64
+	pcpu float64
+}
+
+// To hold the last usage and call time.
+var lu lastUsage
+
+func init() {
+	updateUsage()
+	periodic()
+}
+
+// Get our usage.
+func getUsage() (now time.Time, cpu time.Duration, rss int64) {
+	var ru syscall.Rusage
+	syscall.Getrusage(syscall.RUSAGE_SELF, &ru)
+	now = time.Now()
+	cpu = time.Duration(ru.Utime.Sec)*time.Second + time.Duration(ru.Utime.Usec)*time.Microsecond
+	cpu += time.Duration(ru.Stime.Sec)*time.Second + time.Duration(ru.Stime.Usec)*time.Microsecond
+	return now, cpu, ru.Maxrss
+}
+
+// Update last usage.
+// We need to have a prior sample to compute pcpu.
+func updateUsage() (pcpu float64, rss int64) {
+	lu.Lock()
+	defer lu.Unlock()
+
+	now, cpu, rss := getUsage()
+	// Don't skew pcpu by sampling too close to last sample.
+	if elapsed := now.Sub(lu.last); elapsed < 500*time.Millisecond {
+		// Always update rss.
+		lu.rss = rss
+	} else {
+		tcpu := float64(cpu - lu.cpu)
+		lu.last, lu.cpu, lu.rss = now, cpu, rss
+		// Want to make this one decimal place and not count on upper layers.
+		// Cores already taken into account via cpu time measurements.
+		lu.pcpu = math.Round(tcpu/float64(elapsed)*1000) / 10
 	}
-	fmt.Sscanf(string(out), "%f %d %d", pcpu, rss, vss)
-	*rss *= 1024 // 1k blocks, want bytes.
-	*vss *= 1024 // 1k blocks, want bytes.
+	return lu.pcpu, lu.rss
+}
+
+// Sampling function to keep pcpu relevant.
+func periodic() {
+	updateUsage()
+	time.AfterFunc(time.Second, periodic)
+}
+
+// ProcUsage returns CPU and memory usage.
+// Note upper layers do not use virtual memory size, so ok that it is not filled in here.
+func ProcUsage(pcpu *float64, rss, vss *int64) error {
+	*pcpu, *rss = updateUsage()
 	return nil
 }