initial commit; an addendum to the countem.sh script

Signed-off-by: Kaiwan N Billimoria <kaiwan.billimoria@gmail.com>

ch6/countem2.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+# countem.sh
+# ***************************************************************
+# * This program is part of the source code released for the book
+# *  "Linux Kernel Programming", 2nd Ed
+# *  (c) Author: Kaiwan N Billimoria
+# *  Publisher:  Packt
+# *  GitHub repository:
+# *  https://github.com/PacktPublishing/Linux-Kernel-Programming_2E
+# *
+# * From: Ch 6 : Kernel and Memory Management Internals Essentials
+# ****************************************************************
+# * Brief Description:
+# * [ADDED LATER]
+# * Counts the total number of processes, user and kernel threads currently
+# * alive on the system, and thus calculates and shows the number of user
+# * and kernel mode stacks currently in existance.
+# *
+# * For details, please refer the book, Ch 6.
+# ****************************************************************
+set -euo pipefail
+
+# First capture the info into temp files
+TMPP=/tmp/.p
+TMPT=/tmp/.t
+ps -A > ${TMPP}
+ps -LAf > ${TMPT}
+
+total_prcs=$(wc -l ${TMPP}|awk '{print $1}')
+printf "1. Total # of processes alive                        = %9d\n" ${total_prcs}
+total_thrds=$(wc -l ${TMPT}|awk '{print $1}')
+printf "2. Total # of threads alive                          = %9d\n" ${total_thrds}
+# ps -LAf shows all kernel threads names (col 10) in square brackets; count 'em
+total_kthrds=$(cat ${TMPT}|awk '{print $10}'|grep "^\["|wc -l)
+printf "3. Total # of kernel threads alive                   = %9d\n" ${total_kthrds}
+printf " (each kthread will have a kernel-mode stack)\n"
+total_uthrds=$((${total_thrds}-${total_kthrds}))
+printf "4. Thus, total # of user mode threads = (2) - (3)    = %9d\n" ${total_uthrds}
+printf " (each uthread will have both a user and kernel-mode stack)\n"
+printf "5. Thus, total # of kernel-mode stacks = (3) + (4)*2 = %9d\n" $((${total_kthrds}+(${total_uthrds}*2)))
+
+rm -f ${TMPP} ${TMPT}
+exit 0