From 3f9c979830b72bb30ca6dcc0384a18be6565d04d Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@sbcglobal.net>
Date: Thu, 26 Jan 2017 00:52:29 -0500
Subject: improve cgswap

---
 cgswap.go | 70 +++++++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 50 insertions(+), 20 deletions(-)

diff --git a/cgswap.go b/cgswap.go
index 3491f17..6fab8ae 100644
--- a/cgswap.go
+++ b/cgswap.go
@@ -1,25 +1,34 @@
+// Copyright (C) 2017 Luke Shumaker <lukeshu@sbcglobal.net>
+
+// Command cgswap displays which cgroups are using swap space.
 package main
 
 import (
-	"sync"
+	"bufio"
 	"fmt"
 	"os"
-	"bufio"
-	"strings"
+	"sort"
 	"strconv"
+	"strings"
+	"sync"
 )
 
-func handleErr(err error) {
-	if err != nil {
-		panic(err)
-	}
-}
+// You may be wondering why this program is so parallel.  Needless
+// complexity, right?  Well, because processes may be very short
+// lived, we want to read each process's info as soon as possible,
+// before it goes away.
 
-type pidinfo struct {
-	VmSwap int
+type cginfo struct {
 	Cgroup string
+	VmSwap int
 }
 
+type cginfos []cginfo
+
+func (l cginfos) Len() int           { return len(l) }
+func (l cginfos) Less(i, j int) bool { return l[i].VmSwap < l[j].VmSwap }
+func (l cginfos) Swap(i, j int)      { l[i], l[j] = l[j], l[i] }
+
 func in_array(needle string, haystack []string) bool {
 	for _, straw := range haystack {
 		if needle == straw {
@@ -31,18 +40,30 @@ func in_array(needle string, haystack []string) bool {
 
 func main() {
 	dir, err := os.Open("/proc")
-	handleErr(err)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
 	fileinfos, err := dir.Readdir(-1)
-	handleErr(err)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
 
-	ch := make(chan pidinfo)
-	dat := make(map[string]int)
+	ch := make(chan cginfo)
+	var infos cginfos
+	cgroup2idx := make(map[string]int)
 	var consumers sync.WaitGroup
 	consumers.Add(1)
 	go func() {
 		for info := range ch {
-			cur, _ := dat[info.Cgroup]
-			dat[info.Cgroup] = cur + info.VmSwap
+			idx, ok := cgroup2idx[info.Cgroup]
+			if ok {
+				infos[idx].VmSwap += info.VmSwap
+			} else {
+				cgroup2idx[info.Cgroup] = len(infos)
+				infos = append(infos, info)
+			}
 		}
 		consumers.Done()
 	}()
@@ -77,7 +98,7 @@ func main() {
 							controllers := strings.Split(parts[1], ",")
 							cgroup := parts[2]
 							if heir == "0" || in_array("name=systemd", controllers) {
-								ch <- pidinfo{VmSwap: swap, Cgroup: cgroup}
+								ch <- cginfo{VmSwap: swap, Cgroup: cgroup}
 								return
 							}
 						}
@@ -90,8 +111,17 @@ func main() {
 	producers.Wait()
 	close(ch)
 	consumers.Wait()
-	for cgroup, vmswap := range dat {
-		fmt.Println(vmswap, "kB", cgroup)
+
+	sort.Sort(infos)
+
+	total := 0
+	for _, info := range infos {
+		total += info.VmSwap
+	}
+	vmswap_width := len(strconv.Itoa(total))
+
+	for _, info := range infos {
+		fmt.Printf("%[1]*d kB  %s\n", vmswap_width, info.VmSwap, info.Cgroup)
 	}
+	fmt.Printf("%[1]*d kB  %s\n", vmswap_width, total, "total")
 }
-//	grep VmSwap /proc/*/status|sed -rn 's|^/proc/([0-9]+)/status:VmSwap:\s*(\S+ \S+)$|\2 \1|p'|while read -r kb _ pid; do echo "$kb $(systemctl status "$pid"|head -n1|awk '{print $2}')"; done
-- 
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