RFC546 - Tenex load averages for July 1973

Network Working Group B. Thomas

Request for Comments: 546 BBN-TENEX

NIC: 17792 10 August 1973

TENEX Load Averages for July 1973

This RFCpresents utilization data for the BBN and ISI TENEX systems

which may be of interest to the network community.

The graph on page 4 summarizes the load at the BBN-TENEX and USC-ISI

Hosts during the work week for the month of July 1973. The weekday

hourly load average [1] for each site is plotted versus the time of

day; the time of day is Eastern Daylight Time.

Interpreting data sUCh as this is tricky business. However, it is

difficult to resist making the following observations:

1. The shapes of the BBN and ISI curves are approximately the same;

furthermore, there is no skew between the curves. This suggests

that the user populations for the two systems have similar working

habits and are acclimated to the same time zone.

2. The significant features of both curves appear to be strongly

correlated with "normal events" in the day of a user living on

East Coast time,suggesting that the load at both sites is

influenced most strongly by such users:

a. the load begins to increase between 7-8 a.m. EDT as users begin

their daily computing;

b. it dips between 10-11 a.m. EDT (smoothed to a smaller rate of

increase in the ISI curve) as users take their coffee break;

c. the load peaks sharply between 1-2 p.m. EDT as users return

from lunch to resume their computing;

d. it decreases as the afternoon continues and as users go home

from work;

e. it reaches a local minimum between 6-7 p.m. EDT (minimum not

present in ISI curve) when most people eat dinner;

f. it increases to an evening peak between 9-10 p.m. EDT as some

users come back from dinner and after dinner activities to

resume their computing.

3. The curve for ISI is smoother than the one for BBN: the "coffee

break" dip appears only as a decrease in slope; the dinner break

and evening peak are completely smoothed out. This smoothing is

probably due to the influence of the West Coast users of the ISI

machine.

4. During July the BBN system was more heavily loaded than the ISI

system. Since the data collected did not include the number of

active jobs it is not possible to determine from the data whether

BBN had more users or just more demanding users.

The data presented on the graph is available as a side effect of the

RSEXEC system. The server programs for the RSEXEC system (RSSER

programs) communicate regularly with one another exchanging status

information. The RSSER program at each site maintains a (dynamic)

data base of the information it collects from the RSSER programs at

other sites. The NETLOAD command of the TENEX EXEC, as well as many

RSEXEC commands, makes use of information in that database.

The raw data for BBN and ISI [2] load curves (as well as data for the

other TENEX sites that run RSSER) was collected by a program which

creates daily load information files by periodically (every 3

minutes) reading load average data from the data base maintained by

RSSER. The monthly summary was produced by a program that analyzes

daily data files.

[The following graph is also available in .PS and .PDF format.]

Weekday Hourly Load Averages

July 1973

^ B BBN-TENEX

I ISI-TENEX

10 +

B

+

+ B

Load

Avg. B

I

+

*

+ I

B I B

B

5 +

B I

I

+ I

B

+ I B

B

I

I I B B

+ I

I B I

B

B I B

+ I I I

B * B

* * I I *

B B

---+--+-----------+-----------+-----------+-----------+>

0-1 AM 6-7 AM 12-1 PM 6-7 PM 12

(midnight) (noon) (midnight)

Time of Day (Eastern Daylight Time)

Endnotes

[1] The TENEX load average is a measure of CPU demand. The load

average is an average of the number of runable processes over a given

time period. For example, an hourly load average of 10 would mean

that (for a single CPU system) at any time during that hour one could

eXPect to see 1 process running and 9 others ready to run (i.e., not

blocked for I/O) waiting for the CPU.

[2] The data for BBN and ISI was chosen for presentation in this RFC

because the BBN and ISI TENEXs are two of the major time-sharing

service hosts on the network.

[ This RFCwas put into machine readable form for entry ]

[ into the online RFCarchives by Jim Larson 3/98 ]