Calcolo accurato dell'utilizzo della CPU dato in percentuale in Linux?

Secondo il codice sorgente htop, i miei presupposti sembrano validi:

(vedi static inline double LinuxProcessList_scanCPUTime(LinuxProcessList* this) funzione su LinuxProcessList.c)

// Guest time is already accounted in usertime
usertime = usertime - guest;                             # As you see here, it subtracts guest from user time
nicetime = nicetime - guestnice;                         # and guest_nice from nice time
// Fields existing on kernels >= 2.6
// (and RHEL's patched kernel 2.4...)
unsigned long long int idlealltime = idletime + ioWait;  # ioWait is added in the idleTime
unsigned long long int systemalltime = systemtime + irq + softIrq;
unsigned long long int virtalltime = guest + guestnice;
unsigned long long int totaltime = usertime + nicetime + systemalltime + idlealltime + steal + virtalltime;

E così, dai campi elencati nella prima riga di /proc/stat :(vedere la sezione 1.8 della documentazione)

     user    nice   system  idle      iowait irq   softirq  steal  guest  guest_nice
cpu  74608   2520   24433   1117073   6176   4054  0        0      0      0

Algoritmicamente, possiamo calcolare la percentuale di utilizzo della CPU come:

PrevIdle = previdle + previowait
Idle = idle + iowait

PrevNonIdle = prevuser + prevnice + prevsystem + previrq + prevsoftirq + prevsteal
NonIdle = user + nice + system + irq + softirq + steal

PrevTotal = PrevIdle + PrevNonIdle
Total = Idle + NonIdle

# differentiate: actual value minus the previous one
totald = Total - PrevTotal
idled = Idle - PrevIdle

CPU_Percentage = (totald - idled)/totald

Quello che segue è uno script bash basato sulla risposta di Vangelis. Produce un output come questo:

total 49.1803
cpu0 14.2857
cpu1 100
cpu2 28.5714
cpu3 100
cpu4 30
cpu5 25

Crea un file chiamato get_cpu_usage.sh

Eseguilo usando il seguente comando:bash get_cpu_usage.sh 0.2

L'argomento è il numero di secondi da misurare. In questo caso sono 200 millisecondi.

I contenuti sono:

#!/bin/sh

sleepDurationSeconds=$1

previousDate=$(date +%s%N | cut -b1-13)
previousStats=$(cat /proc/stat)

sleep $sleepDurationSeconds

currentDate=$(date +%s%N | cut -b1-13)
currentStats=$(cat /proc/stat)    

cpus=$(echo "$currentStats" | grep -P 'cpu' | awk -F " " '{print $1}')

for cpu in $cpus
do
    currentLine=$(echo "$currentStats" | grep "$cpu ")
    user=$(echo "$currentLine" | awk -F " " '{print $2}')
    nice=$(echo "$currentLine" | awk -F " " '{print $3}')
    system=$(echo "$currentLine" | awk -F " " '{print $4}')
    idle=$(echo "$currentLine" | awk -F " " '{print $5}')
    iowait=$(echo "$currentLine" | awk -F " " '{print $6}')
    irq=$(echo "$currentLine" | awk -F " " '{print $7}')
    softirq=$(echo "$currentLine" | awk -F " " '{print $8}')
    steal=$(echo "$currentLine" | awk -F " " '{print $9}')
    guest=$(echo "$currentLine" | awk -F " " '{print $10}')
    guest_nice=$(echo "$currentLine" | awk -F " " '{print $11}')

    previousLine=$(echo "$previousStats" | grep "$cpu ")
    prevuser=$(echo "$previousLine" | awk -F " " '{print $2}')
    prevnice=$(echo "$previousLine" | awk -F " " '{print $3}')
    prevsystem=$(echo "$previousLine" | awk -F " " '{print $4}')
    previdle=$(echo "$previousLine" | awk -F " " '{print $5}')
    previowait=$(echo "$previousLine" | awk -F " " '{print $6}')
    previrq=$(echo "$previousLine" | awk -F " " '{print $7}')
    prevsoftirq=$(echo "$previousLine" | awk -F " " '{print $8}')
    prevsteal=$(echo "$previousLine" | awk -F " " '{print $9}')
    prevguest=$(echo "$previousLine" | awk -F " " '{print $10}')
    prevguest_nice=$(echo "$previousLine" | awk -F " " '{print $11}')    

    PrevIdle=$((previdle + previowait))
    Idle=$((idle + iowait))

    PrevNonIdle=$((prevuser + prevnice + prevsystem + previrq + prevsoftirq + prevsteal))
    NonIdle=$((user + nice + system + irq + softirq + steal))

    PrevTotal=$((PrevIdle + PrevNonIdle))
    Total=$((Idle + NonIdle))

    totald=$((Total - PrevTotal))
    idled=$((Idle - PrevIdle))

    CPU_Percentage=$(awk "BEGIN {print ($totald - $idled)/$totald*100}")

    if [[ "$cpu" == "cpu" ]]; then
        echo "total "$CPU_Percentage
    else
        echo $cpu" "$CPU_Percentage
    fi
done